Permanent Magnet FAQ — Specifications, MOQ & Lead Times

Neodymium Magnet Safety

The neodymium magnets we sell are extremely strong. They must be handled with care to avoid personal injury or damage to the magnets.

Powerful attraction forces can cause serious injury.

Neodymium magnets are more powerful than other kinds of magnets.  The incredibly powerful force between magnets can often be surprising to those unfamiliar with their strength.

Fingers and other body parts can be pinched between two magnets.  With larger magnets, injuries of this type can be severe.

Neodymium magnets are not for children.

Neodymium magnets are not toys.  Children should not be allowed to handle neodymium magnets.  Small magnets can pose a choking hazard.  If multiple magnets are swallowed, they can attach to one another through intestine walls.  This can cause a severe health risk, requiring immediate, emergency surgery if correctly diagnosed.

Neodymium magnets can affect pacemakers.

The strong magnetic fields near a neodymium magnet can affect pacemakers, ICDs and other implanted medical devices.  Many of these devices are made with a feature that deactivates it with a magnetic field.  Therefore, care must be taken to avoid inadvertently deactivating such devices.

Neodymium magnets are brittle and fragile.

Neodymium magnets are made of a hard, brittle material.  Despite being made of metal, and the shiny, metallic appearance of their nickel plating, they are not as durable as steel.

Neodymium magnets can peel, chip, crack or shatter if allowed to slam together.  Eye protection should be worn when handling magnets, since shattering magnets can launch small pieces at great speeds.

Neodymium magnets are not easily drilled or machined.

Magnets can affect magnetic media.

The strong magnetic fields near neodymium magnets can damage magnetic media such as floppy disks, credit cards, magnetic I.D. cards, cassette tapes, video tapes or other such devices. They can also damage televisions, VCRs, computer monitors and CRT displays. Avoid placing neodymium magnets near electronic appliances.

Neodymium magnets can become demagnetized at high temperatures.

While operating temperatures are often listed as 80°C (175°F), the actual maximum operating temperature of a magnet can vary depend on the grade, magnet shape and how it is used.

Neodymium magnet powder or dust is flammable.

Avoid drilling or machining neodymium magnets.  When ground into a dust or powder, this material is highly flammable.

Those with nickel allergies should avoid prolonged contact with magnets.

A small percentage of people have a nickel allergy, where an allergic reaction can cause redness and a skin rash.  Those with nickel allergies should avoid directly handling nickel plated neodymium magnets.

Strong magnetic fields can interfere with compasses and navigation.

IATA (International Air Transport Association) and US Federal rules and regulations cover shipping magnets by air and ground delivery.  Magnetic fields can influence compasses or magnetometers used in air transport.  They can also affect internal compasses of smartphone and GPS devices.

Neodymium magnets can corrode.

Neodymium magnets can rust or corrode in the presence of moisture.  While the three layer, nickel-copper-nickel plating on most of our magnets provides enough protection for many applications, they are not waterproof.  If used underwater, outdoors or in a moist environment, they can corrode and lose magnetic strength

Magnet Design Considerations

Basic problems of permanent magnet design revolve around estimating the distribution of magnetic flux in a magnetic circuit, which may include permanent magnets, air gaps, high permeability conduction elements, and electrical currents.

Basic problems of permanent magnet design revolve around estimating the distribution of magnetic flux in a magnetic circuit, which may include permanent magnets, air gaps, high permeability conduction elements, and electrical currents. Exact solutions of magnetic fields require complex analysis of many factors, although approximate solutions are possible based on certain simplifying assumptions. Obtaining an optimum magnet design often involves experience and tradeoffs.

Finite Element Analysis

Magnetic Design has become a critical feature of Magnet Ap- plications growth and we seek to work with our customers to real- ize their ideas. Finite Element Analysis(FEA) modeling programs are used to analyze magnetic problems

in order to arrive at more exact solutions, which can then be tested and fine tuned against a prototype of the magnetic structure. Using FEA models flux densities, torques, and forces may be calculated. Results can be output in various forms, including plots of vector magnetic potentials, flux density maps, and flux path plots.

Magnet Applications uses a suite of 2D and 3D transient FEA modeling packages backed-up with in house design software and many years experience, not just in magnetics but also in general engineering expertise. This allows us to undertake a wide range of design con- tracts and across many industries including automotive, defense, and across many applications including sensors, Brushless DC (BLDC) motors. The length of design contract ranges from a few hours to many days and we pride ourselves on the cost effectiveness of this service.

The BH Curve

The basis of magnet design is the BH curve, or hysteresis loop, which characterizes each magnet material. This curve describes the cycling of a magnet in a closed circuit as it is brought to saturation, demagnetized, saturated in the opposite direction, and then demagnetized again under the influence of an external magnetic field.

The second quadrant of the BH curve, commonly referred to as the “Demagnetization Curve”, describes the conditions under which permanent magnets are used in practice. A permanent magnet will have a unique, static operating point if air-gap dimensions are fixed and if any adjacent fields are held constant. Otherwise, the operating point will move about the demagnetization curve, the manner of which must be accounted for in the design of the device.

The three most important characteristics of the BH curve are the points at which it intersects the BH axes (at Br – the residual induction – and Hc – the coercive force – respectively), and the point at which the product of BH are at a maximum (BH max – the maximum energy product). Br represents the maxi- mum flux the magnet is able to produce under closed circuit conditions. In actual useful operation permanent magnets can only approach this point. Hc represents the point at which the magnet becomes demagnetized under influence of an externally applied magnetic field. BH max represents the point at which the product of BH, and the energy density of the magnetic field into the air gap surrounding the magnet, is at a maximum. The higher this product, the smaller need be the volume of the magnet. Designs should also account for the variation of the BH curve with temperature.

Measurement of BH curves requires specialist equipment. The most common types are DC Hyteresis graphs (Permeameter) where the magnet is driven around its BH loop in a DC electromagnet with sensing coils to the measure the BH of the magnet. Magnet Ap- plications has a temperature controlled permeameter which can BH curves at temperatures from ambient up to 150°C. We use this data to qualify our materials and to supply accurate material data for our design software.

Magnet Assembly Considerations

The following points should be considered when designing magnet assemblies. Proper affixing, fastening, potting and welding methods protect both the magnets and the people handling them.

The following points should be considered when designing magnet assemblies.

Affixing Magnets to Housings

Magnets can be successfully affixed to housings using adhesives. Cyanoacrylate adhesives which are rated to temperatures up to 180° C with fast cure times avoid the need for fixtures to hold the magnets in place while the bond cures. Adhesives with higher temperature ratings are also available, but these require oven curing and fixturing of the magnets to hold them in a vacuum. Potential outgassing of the adhesives should be considered.

Mechanical Fastening

When arrays of magnets must be assembled, especially when the magnets must be placed in repelling positions, it is very important to consider safety issues. Modern magnet materials such as the Rare Earths are extremely powerful, and when in repulsion they can behave as projectiles if adhesives were to break down. It is recommended that in these situations mechanical fastening be included in the design in addition to adhesives. Potential methods of mechanical retention include encasement, pinning, or strapping the magnets in place with non-magnetic metal components.

Potting

Magnet assemblies may be potted to fill gaps or to cover entire arrays of magnets. Potting compounds cure to hard and durable finishes and are available to resist a variety of environments, such as elevated temperatures, water flow, etc. When cured, the potting compounds may be machined to provide accurate finished parts.

Welding

Assemblies which are required to be hermetically sealed can be welded using either laser welding (which is not affected by the presence of magnetic fields) TIG welding (using appropriate shunting elements to reduce the effect of magnetic fields on the weld arc). Special care should be taken when welding magnetic assemblies so that heat dissipation of the weld does not affect the magnets.

Permanent Magnet Stability & Changes

Permanent magnets can experience changes in performance due to circuit reluctance, adverse fields, shock, temperature, machining and coatings. Understanding these factors helps engineers design reliable magnetic systems.

Reluctance Changes

These changes occur when a magnet is subjected to permeance changes such as changes in air gap dimensions during operation. These changes will change the reluctance of the circuit, and may cause the magnet’s operating point to fall below the knee of the curve, causing partial and/or irreversible losses. The extent of these losses depend upon the material properties and the extent of the permeance change. Stabilization may be achieved by pre-exposure of the magnet to the expected reluctance changes.

Adverse Fields

External magnetic fields in repulsion modes will produce a demagnetizing effect on permanent magnets. Rare Earth magnets with coercive forces exceeding 15KOe are difficult to affect in this manner. However, Alnico which has a lower coercive force will encounter magnetic losses in the presence of any magnetic repelling force, including similar magnets. Applications involving Ceramic magnets with coercive forces of 4KOe should be carefully evaluated in order to assess the effect of external magnetic fields.

Shock, Stress and Variation

Below destructive limits, these effects are very minor on modern magnet materials. However, rigid mag- net materials are brittle in nature and can be easily damaged or chipped by improper handling. Samarium Cobalt in particular is a fragile material and special handling precautions must be taken to avoid damage. Thermal shock when Ceramics and Samarium Cobalt magnets are exposed to high temperature gradients can cause fractures within the material and should be avoided.

Physical Characteristics and Machining of Magnets

Sintered Samarium Cobalt and Ceramic magnets exhibit small cracks within the material that occur dur- ing the sintering process. Provided that cracks do not extend more than halfway through a section, they do not normally affect the operation of the magnet. This is also true from small chips that may occur during machining and handling of these magnets, especially on sharp edges. Magnets may be tumbled to break the edges, this is done to avoid “feathering’ of sharp edges due to the brittle nature of materials. Tumbling can achieve edge breaks of 0.003” to 0.010”. Although sintered NdFeB is relatively tough as com- pared to Samarium Cobalt and Ceramic, it is still brittle and care must be taken in handling. Bonded NdFeB is not as brittle as the sintered materials but it is softer and must be handled with care as well. Because of these inherent material characteristics, it is not advisable to use any permanent magnet material as a structural component of an assembly.
Rare Earth, Alnico, and Ceramic magnets are machined by grinding, which may considerably affect the magnet cost. Maintaining simple geometries and wide tolerances is therefore desirable from an economic point of view. Rectangular or round sections are preferable to complex shapes. Square holes (even with large radii) and very small holes are difficult to machine and should be avoided. Magnets may be ground to virtually any specified tolerance. However, to reduce cost, tolerances of less than 0.001” should be avoided if possible.
Cast Alnico materials exhibit porosity as a natural con- sequence of the casting process. This may become a problem with small shapes which are machined out of larger casting, but can account for a large portion of the smaller fabricated magnets. This may cause a problem where uniformity or low variation is critical and it may be advisable either to use a sintered Alnico or another material. In spite of its slightly lower magnetic properties, sintered Alnico may yield a higher or more uniform net density, resulting in equal or higher magnetic output.
In applications where the cosmetic qualities of the magnet are of a concern, special attention should be placed on selecting the appropriate material, since cracks, chips, pores, and voids are common in rigid magnet materials.

Coatings

Samarium Cobalt, Alnico, and Ceramic materials are corrosion resistant and do not require to be coated against corrosion. Alnico is easily plated for cosmetic qualities and Ceramics may be coated to seal the surface which will otherwise be covered by a thin film of ferrite powder.
NdFeB magnets, both sintered and bonded, are susceptible to corrosion and consideration should be given to the operating environment to determine if coating is necessary. Nickel or tin plating may be used for NdFeB magnets, however, the material must be properly prepared and the plating process properly controlled for successful plating.
Aluminum Chromate or Cadmium Chromate vacuum deposition (PVD) is a successful process that can provide a coating thickness as low as 0.0003”. Teflon, Parylene, various epoxies and other organic coatings are relatively inexpensive and are also successful as NdFeB coatings. A further option for critical applications is to apply two types of protective coatings or to encase the magnet in a stainless steel or other housing to reduce the chances of corrosion.
The effectiveness of coatings on customer’s parts can be tested in Magnet Applications Temperature and Humidity Controlled Environmental Chamber. For further information please contact our sales team.

Permanent Magnet Rotor Assemblies

Empire Magnetics specializes in the manufacturing of magnets and magnetic assemblies, providing cutting-edge solutions for a wide range of applications. Our permanent magnet rotor assemblies are designed for BLDC motors, generators, and more, made from the finest quality materials including NdFeB and multi-pole ring magnets.

Understanding Permanent Magnet Rotor Assemblies

Permanent magnet rotor assemblies are critical components in various applications, including BLDC motors, generators, and magnetic couplings. They consist of a rotor equipped with permanent magnets (such as NdFeB) to ensure efficient and reliable magnetic field generation. The interaction between the magnetic fields produced by the rotor and the stator (the stationary part of the motor or generator) enables the conversion of electrical energy to mechanical energy, or vice versa.

Empire Magnetics' permanent magnet rotor assemblies utilize NdFeB and multi-pole ring magnets, making them the ideal choice for those seeking high-quality, reliable, and efficient magnetic solutions for their BLDC motors and other applications. We also offer metal sleeve and carbon fiber sleeve solutions.

High-Performance Permanent Magnets

Our rotor assembly portfolio includes rare earth magnets such as NdFeB and SmCo to ensure maximum magnetic field strength and superior performance. Our multi-pole ring magnets provide uniform magnetic fields that help improve motor efficiency. In addition to radially magnetized ring magnets, we also offer polar anisotropic ring magnets (also known as Halbach ring magnets). We also produce laminated magnets suitable for high-temperature motor applications.

Strict Quality Control

From raw material selection to final product testing, we maintain strict quality control measures throughout the entire production process. This commitment to quality ensures that our permanent magnet rotor assemblies meet or exceed industry standards and customer expectations.

Multi-pole ring magnet rotor magnetic field distribution test

Rotor Retaining Sleeves

We recognize the importance of rotor retaining sleeves in high-speed SPM machines, as they play a crucial role in preventing structural failure. To meet various requirements, we offer multiple rotor sleeve options, including stainless steel, titanium alloy, Inconel, and carbon fiber. Our sleeves are designed to accommodate segment magnets and ring magnets, providing flexibility and efficiency for different permanent magnet rotor configurations.

Engineering Halbach Arrays for Peak-Performance Magnetic Systems

We work with engineers to prototype and produce Halbach magnetic assemblies. For researchers and students, we also offer standard Halbach assemblies available for immediate purchase.

Introduction to Halbach Arrays

A Halbach array is a special arrangement of permanent magnets that enhances the magnetic field on one side while weakening it on the other. This principle was first invented by James (Jim) M. Winey at Magnepan in 1970.

However, it was Klaus Halbach, a German physicist, who designed the Halbach array during his time at Berkeley Lab. Although Mr. Halbach was highly successful as a particle accelerator designer, he is best known for his work on particle accelerator magnetic systems. In the 1980s, he invented this special magnet arrangement for focusing the electron beams of accelerators.

Applications of Halbach Array Assemblies

Halbach assemblies are widely used across various industries due to their unique magnetic field characteristics, which enhance performance in applications such as:

• High-Performance Motors: To achieve lightweight and high-performance motors, Halbach arrangements of NdFeB magnets are commonly used in rotor assemblies. We have manufactured Halbach rotor assemblies for motors used in robotics and medical equipment.
• Synchrotron Light Sources: Halbach arrays are used in synchrotron light sources to produce highly focused, intense magnetic fields. These fields are essential for bending the path of charged particles, which then emit synchrotron light.
• Synchrotron Radiation: In synchrotron radiation production, Halbach arrays create the required magnetic environment to accelerate particles to high speeds, producing valuable radiation for various analytical techniques.
• Accelerators: In particle accelerators, Halbach arrays focus and guide particle beams. Their ability to produce strong, uniform magnetic fields with minimal stray fields makes them ideal for undulators and wigglers.
• Flywheel Energy Storage: Halbach arrays improve the efficiency and performance of flywheel energy storage systems by concentrating the magnetic field on one side, reducing energy loss and improving overall storage capacity.
• Superconducting Magnetic Bearings: Superconducting magnetic bearings use Halbach arrays to achieve stable, frictionless levitation of rotors, ideal for applications requiring minimal friction and high precision.
• Passive Magnetic Bearings: For passive magnetic bearings, Halbach arrays provide the necessary magnetic field to support and stabilize rotating shafts without physical contact, reducing maintenance requirements.
• Magnetocaloric Heat Generation: The magnetocaloric effect can be used in heat pumps and energy systems. Halbach arrays, which maximize magnetic field strength on one side, can enhance the efficiency of magnetocaloric systems.

Ensuring Compliance: Halbach Assemblies with Hitachi-Licensed Magnets

To avoid potential legal disputes, companies selling products containing NdFeB magnets in North America or Japan typically mandate the use of Hitachi-licensed neodymium magnets in their assemblies. In China, there are several Hitachi-licensed NdFeB manufacturers. Thanks to our strategic partnerships with some of these licensed manufacturers, we can efficiently source licensed magnets (even in small batches) and provide Halbach assemblies that comply with local regulations.

Custom Halbach Assemblies by Empire Magnetics

Engineers often require more complex designs for circular Halbach assemblies, meaning most Halbach arrays are custom-built to customer specifications. At Empire Magnetics, we have extensive experience in designing and manufacturing Halbach assemblies using NdFeB or SmCo magnets in aluminum or copper housings. With two decades of expertise, we possess the knowledge and skills to assemble magnets precisely and efficiently, ensuring optimal performance and customer satisfaction.

Overmolded and Insert-Molded Magnetic Devices

NdFeB magnets are widely used in consumer goods, electronics, automotive, and various other industries. Despite their versatility, these magnets are brittle and susceptible to breakage and corrosion. Encapsulating them in plastic or rubber materials serves the dual purpose of protection and aesthetic enhancement.

Why Overmold NdFeB Magnets?

In consumer goods, electronics, automotive, and various other industries, NdFeB magnets have extensive applications. Despite their versatility, these magnets are brittle and prone to breakage and corrosion. Wrapping them in plastic or rubber materials serves the dual purpose of protection and aesthetic enhancement.

However, not all magnet companies possess expertise in plastic injection molding, and vice versa. This is where Empire Magnetics comes in.

Managing High Temperatures When Overmolding NdFeB Magnets

Insert molding is a plastic injection molding technique in which an insert is placed into the mold cavity and molded with plastic to form a single solid piece. NdFeB magnets are susceptible to high temperatures, which can lead to demagnetization. This risk is particularly pronounced during the plastic injection molding process. The degree to which the magnet surface is exposed to molten plastic at high temperatures determines whether the magnet is pre-magnetized or magnetized after molding. In the latter case, the entire insert-molded piece is placed in a magnetizing coil for magnetization.

Using Non-Magnetic Mold Steel for Insert Molding

If the insert-molded NdFeB magnet is sufficiently thick along its magnetization direction, or if brief exposure to the plastic flow does not cause demagnetization, another issue arises: the magnet may be attracted to the mold steel, which is typically ferromagnetic. If we need to insert a magnetized NdFeB magnet into the mold, we choose non-magnetic mold steel, even though it typically has a shorter mold life. This choice is particularly common for irregularly shaped products that are difficult to fit into magnetizing coils.

Magnetic Wheels: Enabling Mobility and Stability for Climbing Robots

Magnetic wheels are essential components for climbing robots, providing the adhesion and traction needed to traverse ferromagnetic surfaces safely and efficiently.

Magnetic Wheel Design

Determining the torque and speed requirements of the drive system is key to selecting magnetic wheels. The design and material selection must meet user requirements, including maximum torque design values and speed ranges.

Load Torque Design

Optimization of Magnetic Wheels

• Magnetic circuit design optimization: Enhancing torque density through design, such as adding weak magnetic elements inside the magnetic ring, effectively increases external magnetic force, resulting in higher torque compared to similar products.
• Surface treatment: Knurling can increase the surface roughness of the wheel, thereby enhancing the friction of the magnetic wheel. If higher friction is needed during operation, we can add an external rubber sleeve.

Magnetic Material Basis

Magnetic wheels rely on high-performance bonded or sintered NdFeB rings. The magnetic powder morphology and domain alignment directly influence the adhesion force and torque capacity of the final wheel assembly.

Empire Magnetics Standard Round Magnetic Wheels

All dimensions are in millimeters (mm).

Empire Magnetics Standard Arc Magnetic Wheels

*Pull force strength is measured at 0mm, 3mm, and 5mm distance from a steel plate.

All dimensions are in millimeters (mm).

Magnetic Wheel Manufacturer

At Empire Magnetics, we are excited to be an early participant in your new projects. Our passion for magnets extends from material selection and design optimization to providing magnetic solutions. We hope to bring our knowledge and experience to the forefront by actively participating in your upcoming projects. Work with our magnet experts to get the right magnetic solution.

Image credits: Cililun & Fzmag & Climbing-robots

Polar Anisotropic Ring Magnets: Better Than Radial Ring Magnets for BLDC Motors

Polar anisotropic ring magnets are a type of multi-pole ring magnet that exhibit higher magnetic flux density compared to radially anisotropic ring magnets of the same material grade and dimensions. This key advantage has led motor designers to increasingly choose these innovative multi-pole ring magnets over their radially magnetized counterparts.

Introduction: Polar Anisotropic Ring Magnets

A polar anisotropic ring magnet is a type of multi-pole ring magnet that exhibits higher magnetic flux density compared to a radially anisotropic ring magnet of the same material grade and dimensions. This key advantage has prompted motor designers to increasingly select this innovative multi-pole ring magnet over its radially magnetized counterpart in various applications.

The orientation of this type of multi-pole ring magnet is similar to that in a Halbach array, which is why it is also referred to as a "Halbach multi-pole ring magnet." This arrangement results in enhanced magnetic flux density (field strength) on one side of the magnet. Consequently, its magnetic field strength exceeds that of an equivalent radially anisotropic (radially magnetized) ring magnet.

Orientation of Polar Anisotropic Ring Magnets

Advantages and Disadvantages: Polar Anisotropic Ring Magnets for Motors

Advantages

• Polar anisotropic ring magnets have higher magnetic flux density than their radially oriented counterparts, providing enhanced performance in various applications.
• The magnetic flux density on the outer diameter surface of this multi-pole ring magnet displays as a sine wave without a magnetic axis, resulting in improved motor efficiency and reduced material weight.
• The sinusoidal magnetic field around the motor circumference reduces cogging torque, resulting in quieter and smoother operation.

Disadvantages

• The magnetic pole flux density variation of these multi-pole ring magnets is higher than that of radially oriented ring magnets, which may negatively impact performance in certain applications.
• Compared to segmented magnets and radially magnetized ring magnets, these multi-pole ring magnets have higher manufacturing costs, making them a more expensive option for certain applications.

Applications of Polar Anisotropic Multi-Pole Ring Magnets

Polar anisotropic ring magnets are widely used in various industries that require high torque or high-speed performance. These magnets have proven indispensable in many fields, including power tools, robotics, home appliances, medical devices, and more. Each application typically requires a specific number of poles customized to its unique requirements. For example, coreless motors, also known as hollow cup motors, typically use 4-pole ring magnets for optimal functionality and efficiency. The versatility and adaptability of polar anisotropic ring magnets make them the preferred choice for numerous cutting-edge technology and industrial applications.

Parylene Coated Magnets

Parylene coating is a specialized conformal coating technique that provides superior biocompatibility, corrosion resistance, and moisture protection for magnets used in medical, automotive, and aerospace applications.

What is Parylene Coating?

Parylene (poly-para-xylylene) is a protective polymer coating applied through a chemical vapor deposition (CVD) process. Unlike liquid coatings, Parylene is deposited as a gas, forming a truly conformal, pinhole-free film that uniformly coats all exposed surfaces of the magnet, including complex geometries and internal cavities.

For NdFeB and SmCo magnets, Parylene coating offers exceptional protection against moisture, salt spray, and corrosive environments while maintaining extremely thin coating thicknesses (typically 5-50 microns). This makes it particularly valuable for magnets used in medical implants, sensors, and other applications where biocompatibility and miniaturization are critical.

Key Advantages of Parylene Coating

• Biocompatibility: Parylene C and N coatings meet ISO 10993 biocompatibility standards, making them suitable for medical implants and devices that contact human tissue.
• Corrosion resistance: Provides an excellent moisture and chemical barrier, dramatically improving the corrosion resistance of NdFeB magnets in harsh environments.
• Uniform thickness: The CVD process ensures a truly conformal coating with uniform thickness across all surfaces, including edges, corners, and irregular geometries.
• Thin profile: Coating thickness can be controlled from a few microns to tens of microns, minimizing dimensional impact on precision magnet assemblies.
• Dielectric insulation: Parylene offers excellent dielectric properties, providing electrical insulation for magnets used in electronic assemblies.

Raw Material & Corrosion Mechanism

NdFeB magnets begin as fine magnetic powder. Without protection, intergranular corrosion can propagate rapidly in humid or saline environments. Parylene conformal coating seals these boundaries, extending service life in medical and automotive applications.

Parylene Coating Process

The Parylene coating process involves three main steps: vaporization of the dimer, pyrolysis to form the reactive monomer, and polymerization on the magnet surface at room temperature. This process ensures a stress-free, conformal coating without the thermal expansion issues associated with high-temperature coating methods.

Applications of Parylene Coated Magnets

Parylene coated magnets are essential in applications requiring biocompatibility, corrosion resistance, and miniaturization:

• Medical implants: Magnetic sensors, drug delivery devices, hearing implants, and surgical instruments where biocompatibility is critical.
• Automotive sensors: Magnets in engine compartments and underbody applications exposed to moisture, salt, and temperature cycling.
• Aerospace: Magnets in avionics and control systems requiring lightweight, corrosion-resistant protection.
• Consumer electronics: Miniature magnets in smartphones, wearables, and audio devices where thin protective coatings are essential.

Micro Magnets

Micro magnets, also known as miniature magnets, are permanent magnets with dimensions typically below one millimeter. In some cases, dimensions below 0.50mm are required. They can be made from NdFeB (N55 grade), SmCo, AlNiCo, and FeCrCo materials.

Definition of Micro Magnets

Micro magnets, also known as miniature magnets, are permanent magnets with dimensions typically below one millimeter. In some cases, dimensions below 0.50mm are required. They can be made from NdFeB (N55 grade), SmCo, AlNiCo, and FeCrCo magnets.

Among these permanent magnet materials, NdFeB is the most preferred due to its superior magnetic properties. However, NdFeB magnets are susceptible to corrosion, requiring surface coating. One of the challenges in manufacturing micro NdFeB magnets lies in surface coating. For medical applications, special coatings such as tin, gold, and Parylene are required. SmCo magnets are characterized by high temperature resistance and excellent stability. AlNiCo magnets are typically chosen for their temperature stability.

Applications of Micro Magnets

Applications in Magnetic Implant Devices

Micro magnets are transforming medical technology, providing innovative solutions for healthcare challenges. These miniature devices are driving the development of implantable medical technology, with the potential to improve patient outcomes and enable more precise treatments. Key advancements include:

• Miniaturization: Compact, powerful magnetic devices suitable for minimally invasive surgery.
• Wireless functionality: Charging and data transmission without physical connections.
• Diverse applications: From regulating fluid flow in hydrocephalus to enhancing cochlear implants.
• Safety advances: Sealing technology and MRI compatibility ensure patient safety.
• Future potential: Expanding uses in cardiac support, drug delivery, and other medical fields.

As research progresses, micro magnets will play an increasingly important role in healthcare and technological advancement.

Applications in Cardiovascular Medicine

In the field of cardiovascular medicine, micro magnets are revolutionizing treatment methods. They can improve imaging precision, enable targeted therapy, control thrombi, guide minimally invasive procedures, and provide innovative diagnostics. These micro magnets are reshaping heart health, bringing a brighter future for patients.

Applications in Sensors

Micro magnets are used in sensors to detect and measure physical properties such as magnetic fields, temperature, pressure, and acceleration.

Micro Magnetic Engineering

In an ever-shrinking technological world, the demand for components that match this trend is evident. Enter micro magnetic engineering, a discipline dedicated to the design and implementation of tiny magnetic materials across various applications. This field explores the roles and applications of four permanent magnet materials: Sm2Co17, NdFeB N55, AlNiCo, and FeCrCo.

Single-Pole Radially Magnetized Ring Magnets

Single-pole or monopole radially magnetized ring magnets are a remarkable and highly specialized type of magnet designed for specific applications. In this article, we explore the unique properties and applications of these fascinating magnets.

Characteristics of Single-Pole Radial Ring Magnets

Radially magnetized ring magnets are produced from oriented NdFeB powder and magnetized so that the field vector points from the inner diameter to the outer diameter (or vice versa). This one-pole configuration is ideal for rotary encoders, high-speed motors, and precision magnetic couplings.

Radially magnetized magnets are unique. Unlike ordinary ring magnets that have north and south poles on flat surfaces, the magnetic field of a radially magnetized ring magnet is distributed circularly or radially within the ring. This is achieved by aligning the magnetic domains in the radial direction.

At first glance, these magnets may look like standard ring magnets, but their true distinction lies in the magnetization method. As the name suggests, a single-pole radially magnetized ring magnet has only one magnetic pole on the inner diameter, while the outer diameter acts as the opposite pole. This special monopole configuration sets them apart and opens up many possibilities for uses that ordinary magnets cannot handle.

Single-Pole Radial Ring Magnet Specifications

The specifications of single-pole radial ring magnets can vary significantly depending on the specific application and design requirements. Below is the general range of these dimensions:

• Outer Diameter (OD): Ranging from a few millimeters (e.g., 2-3mm) to several inches (e.g., up to 6 inches or more), depending on customer requirements.
• Inner Diameter (ID): The inner diameter is a few millimeters smaller than the outer diameter.
• Height (H): From 0.5mm to several millimeters, e.g., 10mm.

We can custom-produce radially magnetized ring magnets according to your needs. Since one-time tooling costs are incurred, if the dimensions are close to your requirements, we recommend purchasing samples from our existing radial ring magnet inventory.

Applications of Single-Pole Radial Ring Magnets

The single-pole radial magnetization pattern is achieved by aligning magnetic domains in the radial direction, providing a uniform field around the circumference.

The unique characteristics of these magnets have several interesting implications and applications:

• Precision positioning: Single-pole radial ring magnets excel in precision positioning for rotary encoders. Their monopole design provides accurate and consistent feedback, which is essential for applications requiring high-precision positioning such as robotics and automation. They help ensure precise control in CNC machines, where accurate positioning is critical to the manufacturing process.
• AI data center cooling: Used in motors for cooling AI data computing centers.

Our Inventory of Single-Pole Radial Ring Magnets

Radial Ring Magnet Supplier - Empire Magnetics

At Empire Magnetics, we are excited to be an early participant in your new projects. Our passion for magnets extends from material selection and design optimization to providing magnetic solutions. We hope to bring our knowledge and experience to the forefront by actively participating in your upcoming projects.

Empire Magnetics works closely with design engineers, participating in review, optimization, and manufacturing of precision permanent magnets, multi-pole ring magnets, Halbach arrays, soft magnetic composite components, and custom magnetic assemblies — from early prototype development through full-volume production.

Trusted by engineers across medical, robotics, aerospace, and industrial automation industries in Europe, America, and Asia.

Frequently Asked Questions