Neodymium Magnet Guide: Grades, Shapes and Motor Applications

Quick answer: A neodymium magnet is a permanent magnet produced from a neodymium-iron-boron (NdFeB) alloy. In its sintered form it belongs to the strongest commercial permanent magnet family, with a maximum energy product of roughly 23-53 MGOe across the grade range a specialist factory manufactures. Grade codes such as N42SH or 48EH carry two different pieces of information at once - magnetic strength and resistance to demagnetization at temperature - which is why the highest number on a datasheet is not automatically the right choice for a motor, sensor or magnetic assembly.

This guide is written for buyers and engineers who are at the research stage: you know a permanent magnet will be part of the design, and you need to understand what you are actually specifying before you contact suppliers. It explains what sintered NdFeB magnets are, where they are used, how grades, shapes and coatings are selected, how a magnet factory is qualified, and what should be validated before a production order is placed.

Sintered NdFeB permanent magnets are supplied as blocks, discs, rings, arcs, trapezoids and customer-specific shapes. Image: JLmagnet.

Why "Neodymium Magnet" Is Harder to Specify Than It Looks

The difficulty is rarely the material itself. Sintered NdFeB is a well-established permanent magnet category, and its basic behaviour is predictable. The difficulty lies in four layers of detail that all interact with each other.

1. The grade code combines two properties. A designation such as N42SH, 48H or N48EH encodes both a magnetic strength level and a temperature class. The letter groups - M, H, SH, UH, EH and AH - correspond to progressively higher intrinsic coercivity (Hcj), which is what resists demagnetization when the magnet gets hot. A strong grade with a low coercivity class and a slightly weaker grade with a high coercivity class can behave completely differently in the same motor.
2. Temperature and the magnetic circuit interact. Where a magnet actually sits in the circuit determines its operating temperature, not the ambient temperature of the device. The practical check is the hot demagnetization curve - Hcj at the working temperature - rather than the room-temperature grade alone.
3. Form and magnetization direction change the assembly, not just the magnet. An integrated radial or multipole ring can replace a set of glued segments, which removes a gluing step and improves concentricity and dynamic balance. That decision belongs in the specification phase, because it changes tooling, tolerances and cost structure.
4. Supplier differences are invisible on a spec sheet. Two suppliers can quote the same grade and the same drawing, yet differ in magnetic property fluctuation lot to lot, dimensional pass rate, coating adhesion, and whether a magnetic property test report travels with each batch. These are the differences that show up months later in production.

For a buyer in the research stage, the practical conclusion is that a neodymium magnet should be specified as a system component - grade, geometry, magnetization, coating and documentation together - rather than as a commodity item chosen by price per kilogram.

Industry Background: Where Sintered NdFeB Magnets Are Used

Sintered NdFeB permanent magnets serve automotive, consumer electronics, synchronous motor, wind power, medical device, aerospace and general magnetic application industries. Their function is usually as rotor or stator magnets, sensor elements, or key components inside magnetic chucks, separators and coupling assemblies. Because the material delivers high energy density in a small volume, it is normally selected when torque density, weight or installation space matter more than the lowest possible material cost.

This is also why the comparison with older magnet families is not a simple quality ranking. Sintered NdFeB offers the highest energy product among commercial permanent magnets, which enables smaller, lighter and more efficient motors - relevant for drive motors, electric power steering (EPS) and robotics. Ferrite magnets remain cheaper for cost-sensitive, low-performance applications, and the choice between them depends on torque density targets and cost targets, not on one material being universally better.

Two structural trends shape current sourcing behaviour. First, motors and generators increasingly run hotter and faster, so demand has shifted toward high-coercivity classes (SH, UH, EH and AH) and toward grain-boundary-diffusion grades that reach high operating temperatures with less heavy rare earth. Second, rare earth export controls and supply-chain localisation have made heavy-rare-earth content a compliance question as much as a technical one. Buyers increasingly ask for Dy/Tb-free formulations, export compliance documentation, and buffer-stock planning alongside the technical datasheet.

The Supplier Side: What a Sintered NdFeB Magnet Factory Provides

Ningbo Jinlun Magnet Technology Co., Ltd. (brand name JLmagnet, website jlmagnet.com) is a Chinese manufacturer of sintered NdFeB permanent magnets. The company was founded in 1996 as Cixi Jiwei Magnetoelectric Material Factory and formally incorporated in 2006, and has over 30 years of experience in the R&D, production and sales of sintered NdFeB magnets. It is based in Cixi, Ningbo, Zhejiang Province, and is a national high-tech enterprise as well as a national-level "Specialized, Refined, Distinctive and Innovative Little Giant" enterprise.

Manufacturing takes place across two production sites covering a total factory area of approximately 80,000 m², with approximately 400 employees, including an R&D team of 45 engineers and technicians. Annual production capacity reaches 8,000 tons of high-performance magnets. The company owns full vertical production capacity covering melting, hydrogen-decrepitation, powder preparation, pressing, sintering, precision CNC machining, multi-type surface treatment and final performance testing - so blank production, machining, plating and testing are not outsourced across separate suppliers. Digital-intelligent workshops run on ERP, MES and WMS systems to achieve full-lot traceability from raw material input to finished-product delivery.

Accreditations cover IATF 16949 (automotive quality management, obtained in 2019), ISO 9001 (quality management), ISO 14001 (environmental management) and an Intellectual Property Management System. The company holds over 60 invention and utility-model patents covering magnet formulation, grain-boundary diffusion, machining processes and tooling devices. Its NdFeB materials for new-energy vehicle motors were selected as "Made in Zhejiang Excellence". Exports account for approximately 30% of company revenue, mainly to Europe, America and other overseas markets, with magnets shipped to more than 20 countries and regions.

Product forms and shapes

The structural configuration includes discs, cylinders, rings, blocks, arcs (tiles), trapezoids, multipole radial rings, Halbach components and custom shapes. Product model codes follow a naming convention in which the shape letter and dimensions are combined - for example D (disc or column), F (block) and R (arc) - with features such as steps, holes or chamfers appended after a hyphen. Documented examples include D15×3.8 (disc), D50×D13.5×20-D20×8 (ring with counterbore), F18×9.5×2 (block) and R90×R85×40×50 (arc).

Multipole NdFeB ring magnets, such as the 42H OD25 × ID16 × H5 mm type with 8 or 12 poles, are used in encoders, BLDC servo motors, EPS motors, spindle motors and magnetic coupler assemblies.

Standard geometries are only part of the offer. The engineering team supports full shape customisation - blocks, rings, arcs and more complex parts - together with custom magnetization patterns such as radial, multipole and Halbach orientations, and magnetic-circuit simulation, magnetic-field analysis and material-selection optimisation for customers who need the magnet designed into a specific magnetic circuit.

Grade coverage and temperature classes

The manufactured grade range covers N25-N58, 33M-56M, 30H-56H, 30SH-56SH, 30UH-54UH, 28EH-48EH and 28AH-42AH. Across this range, remanence (Br) runs from approximately 9.6 to 14.7 kGs (0.96 to 1.47 T) and maximum energy product from 23 to 53 MGOe. Intrinsic coercivity thresholds are ≥12 kOe for N and M classes, ≥16 kOe for H, ≥20 kOe for SH, ≥25 kOe for UH and ≥30 kOe for EH.

Maximum working temperature follows the class: 70-80°C for N, 100°C for M, 120°C for H, 150°C for SH, 180°C for UH and 200°C for EH, with grain-boundary-diffusion grades used for the highest-temperature applications. The company also develops heavy-rare-earth-free formulations that maintain high coercivity and energy product with less than 0.1% heavy rare earths and remain stable from -50°C to 150°C, and has developed CeFeB hybrid rare-earth technology that saves 30%-50% of critical rare earths. Its grain-boundary-diffusion process is reported to raise coercivity by 5-10 kOe while using less than 0.6 wt% heavy rare earth for 200°C applications.

A 45SH segment magnet, model OR32.5 × IR29 × H24.9 × 60°, diametrally magnetized with a standard Ni-Cu-Ni coating for permanent magnet motor assembly.

Coatings and corrosion protection

NdFeB material corrodes if it is left unprotected, so coating choice is part of the specification rather than an afterthought. Multiple anti-corrosion options are available - zinc, nickel, epoxy and parylene coatings - and the company runs an in-house electroplating centre with standard systems including bright Ni-Cu-Ni, matte Ni-Cu-Ni, single-layer Ni, black oxide, colour zinc, chemical Ni and epoxy. Bright or matte Ni-Cu-Ni is the usual choice for general motors, colour zinc or chemical Ni suits cost-sensitive parts, epoxy resins suit high-humidity environments, and Everlube or parylene coatings are used for special conditions. Salt-spray and high-temperature aging tests are part of the reliability testing the in-house test centre supports.

Quality control, testing and consistency

Magnetic performance is controlled within ±2% fluctuation, and the key dimensional pass rate is 99.5%, with magnetic property test reports (Br, Hcj and (BH)max) issued per batch. Typical pre-shipment checks include magnetic property measurement on a BH curve tester, dimensional inspection against the drawing, coating thickness and adhesion checks, salt-spray testing for plated parts, and appearance sampling. The company operates a municipal-level Magnet Engineering & Technology Center certified as a provincial-level laboratory, equipped with more than 300 sets of domestic and imported production and inspection machines, and supports third-party inspection such as SGS or TUV on request. It serves more than 3,000 customers with a repurchase rate above 85%.

Step-by-Step: How to Specify a Neodymium Magnet

Most specification errors are avoidable if the following sequence is followed before a drawing is released.

1. Define the operating condition, not the ambient condition. Establish the maximum temperature the magnet itself will reach, the expected demagnetization field from the coil or armature, and whether the duty cycle is continuous or cyclic.
2. Select the grade family from temperature and demagnetization risk. N or M classes typically suit 70-100°C operation; H (120°C), SH (150°C), UH (180°C) and EH (200°C) classes are used as the thermal requirement rises. For EPS and drive motors, high-coercivity grades such as N38SH, N42SH, 45SH, N48H or UH classes are commonly considered, depending on operating temperature and demagnetization resistance.
3. Choose the form factor against the assembly method. Discs, blocks and arcs cover most motor and sensor layouts; radial rings and multipole rings simplify rotor assembly by removing segment gluing; Halbach and custom assemblies suit specialised magnetic circuits.
4. Fix magnetization direction, pole count and tolerances on the drawing. Pole count, magnetization direction and tolerance requirements must be confirmed before tooling development, because they determine tooling and magnetizing fixtures.
5. Choose the coating for the environment. Match the plating system to humidity, salt exposure and automotive requirements, and request salt-spray data where relevant.
6. Validate with a sample, then scale. Confirm the demagnetization curve at the operating temperature, check dimensional capability, and only then move to batch production with the agreed inspection and documentation package.

Use Cases: Motors, Sensors and Magnetic Assemblies

Automotive auxiliary motors and EPS. A 45SH segment magnet such as OR32.5 × IR29 × H24.9 × 60° is diametrally magnetized and sized for permanent magnet motor assembly, with a maximum continuous operating temperature up to 150°C and a Ni-Cu-Ni coating as standard. Radially oriented rings and multipole rings are also used in automotive auxiliary EPS motors.

Servo motors, spindle motors and automation. Radially oriented NdFeB ring magnets, documented in a 40H OD18 × ID10 × H4 mm, 4/6 pole configuration, are used in small industrial BLDC servo motors and in high-speed spindle motors for automation equipment. Their integrated one-piece design removes segment gluing, improves concentricity and dynamic balance, and produces a smoother sinusoidal field with lower torque ripple.

Encoders, sensors and speed measurement. High-precision magnetic encoders, precision magnetic speed sensors and position sensors are among the most common uses of multipole and radial rings, where stable pole-to-pole consistency matters more than raw strength. A documented multipole ring example is 42H OD25 × ID16 × H5 mm with 8 or 12 poles, holding dimensional tolerance within ±0.05 mm.

Pumps, HVAC and compressors. Segment magnets are used in permanent magnet BLDC motors for industrial pumps, servo motors for automation equipment, high-efficiency electric generators, HVAC fan motors, electric vehicle auxiliary motors and compressor motors for refrigeration.

Magnetic coupling and transmission assemblies. Radially oriented rings suit magnetic couplers and magnetic transmission assemblies, where the integrated ring simplifies rotor assembly and saves assembly cost compared with spliced segment magnets. Block magnets such as the 38M L20×W10×T5 mm type are also used in magnetic coupling assemblies, together with automated door and window actuators.

Generators, medical and aerospace equipment. Wind turbine generators, medical devices and aerospace subsystems use sintered NdFeB magnets as rotor or stator components and sensor elements, where working conditions range from ambient to mid-high temperature, and high-temperature grades are selected per material class.

Comparison Table: NdFeB Grade Families and Temperature Classes

The table below summarises the grade families a sintered NdFeB manufacturer typically offers, together with the intrinsic coercivity threshold and maximum working temperature associated with each class. It is a starting point for selection, not a substitute for checking the demagnetization curve at the actual operating temperature.

Across this grade range, remanence (Br) is approximately 9.6-14.7 kGs (0.96-1.47 T) and maximum energy product is 23-53 MGOe. Custom magnetization, dimensional tolerance and coatings are produced per drawing.

Structural Options at a Glance

Shape selection is driven by how the magnet is mounted and how the field must be oriented. The following table maps documented product forms to their magnetization characteristics and typical applications.

Frequently Asked Questions

Can sintered NdFeB magnets be supplied without heavy rare earths (Dy/Tb-free)?

Yes. Heavy-rare-earth-free formulations are available that maintain high coercivity and energy product with less than 0.1% heavy rare earths and remain stable from -50°C to 150°C. This matters to buyers facing rare earth supply and export-control risk, including European buyers localising supply chains. CeFeB hybrid rare-earth technology has also been developed, saving 30%-50% of critical rare earths. When sourcing under export-control conditions, the practical checks are: confirm the grade and its heavy rare earth content with the supplier, request export compliance documents and shipping history for your destination, plan buffer stock for lead-time fluctuations, prefer low-heavy-rare-earth or heavy-rare-earth-free grades where the design allows, and work with the supplier's documentation team on customs declarations such as HS code and certificate of origin. As a final technical step, ask for the demagnetization curve of the Dy/Tb-free grade at your operating temperature.

Can a supplier provide radial magnetized rings and multipole rings for motors and sensors?

Yes. Multipolar and radial orientation technologies are used to produce multipole rings and radial rings with high pole-to-pole consistency, widely used in small motors, sensors and actuators. Custom magnetization patterns - radial, multipole and Halbach - are available. For motor and sensor projects, confirm the pole count, magnetization direction and tolerance requirements in the drawing before tooling development. Automotive projects should also verify supplier credentials: JLmagnet passed IATF 16949 automotive quality management certification in 2019 and supplies magnets for automotive motors including EPS and drive motors, with NdFeB materials for new-energy vehicle motors selected as "Made in Zhejiang Excellence".

What are the MOQ and commercial terms for an international magnet order?

For standard production, the minimum order quantity is typically 10 kg, with sample orders excluded and confirmed as needed. Common payment terms are T/T, for example 30% deposit with the balance against a copy of the bill of lading, or L/C at sight. Delivery terms are commonly EXW, FOB Ningbo or CIF, and framework agreements with agreed payment schedules can be discussed for long-term cooperation. Incoterms and bank details should always be confirmed in writing. Cost is driven mainly by grade and heavy rare earth content, shape complexity, machining tolerance and coating system, so the same physical size can carry very different pricing depending on these four factors.

How should a sample or first lot be validated before mass production?

Work from the drawing outward. Ask for the demagnetization curve at the operating temperature, not just the room-temperature grade. Typical pre-shipment checks are magnetic property measurement on a BH curve tester, dimensional inspection to the drawing, coating thickness and adhesion checks, salt-spray testing for plated parts, and appearance sampling. Magnetic performance should be controlled within ±2% fluctuation with a key dimensional pass rate of 99.5%, and magnetic property test reports covering Br, Hcj and (BH)max should accompany each batch or lot. Where additional assurance is needed, third-party inspection by organisations such as SGS or TUV can be arranged. Requesting SPC data and demagnetization curves for delivered lots is a reasonable supplier-qualification step.

What lead time should buyers plan for?

Sample orders typically take around 15 days, while batch orders run around 25 days, subject to grade, shape complexity and coating. Schedule confirmations should be made with sales before order placement, and agile response with rapid delivery options is available for qualified customers. To start a technical review, send the drawing, operating temperature, pole count and coating requirement to JLmagnet at sales00@jlmagnet.com to request a sample, a quotation or the full product profile - the 2026 company profile PDF can be downloaded here.

Conclusion: Reducing Risk Before the First Purchase Order

The neodymium magnet family is broad enough that two buyers can order "an N42 neodymium magnet" and receive components that behave quite differently in service. The variables that decide the outcome are known and manageable: the grade family matched to real operating temperature and demagnetization risk, the shape and magnetization pattern matched to the assembly method, the coating matched to the environment, and a supplier whose batch consistency and documentation can be verified rather than assumed.

JLmagnet manufactures sintered NdFeB permanent magnets in blocks, discs, rings, arcs, trapezoids, multipole radial rings, Halbach components and custom shapes, across N, M, H, SH, UH, EH and AH grade families, with in-house melting, sintering, machining, plating and testing, IATF 16949 and ISO 9001 certification, and per-batch magnetic property test reports. Buyers who are still in the research stage can move faster by sending the operating conditions and drawing for technical feedback, magnetic-circuit simulation support and a sample before committing to tooling.

Magnets are inspected and packed before shipment; magnetic property test reports are issued per batch.