Magnetic Materials Knowledge Base
Magnetic Materials Glossary
Concise definitions of common magnetic-materials and application-engineering terms. Each entry links to related products so you can move from concept to selection in one click.
Magnetic properties
Remanence
剩磁Br- The magnetic flux density that remains in a magnetised material after an external magnetising field is removed. Measured in tesla (T) or gauss (G), Br defines the maximum flux the material can supply and is a primary figure of merit for permanent magnets.
Coercivity
矫顽力Hcb- The reverse magnetic field strength required to reduce the magnet's flux density (B) to zero after saturation. Higher Hcb means the magnet better resists partial demagnetisation from external fields. Reported in kA/m or Oe.
Intrinsic coercivity
内禀矫顽力Hcj- The reverse field needed to reduce the material's intrinsic magnetisation (J) to zero. Hcj reflects resistance to irreversible demagnetisation at operating temperature and is the key parameter for selecting magnets used in motors, generators and high-temperature environments.
Maximum energy product
最大磁能积(BH)max- The largest value of B·H on the demagnetisation curve, expressed in kJ/m³ or MGOe. It represents the maximum magnetic energy stored per unit volume and is the headline performance grade of a permanent magnet (e.g. N52 ≈ 52 MGOe).
Curie temperature
居里温度Tc- The temperature at which a ferromagnetic material loses its permanent magnetisation and becomes paramagnetic. Above Tc the magnet cannot function; practical max operating temperatures are well below Tc. NdFeB ≈ 310–400 °C, SmCo ≈ 700–800 °C, ferrite ≈ 450 °C.
Magnetic anisotropy
磁各向异性- Directional dependence of a magnet's magnetic properties. Anisotropic magnets are aligned during pressing so the easy axis points in one direction, yielding much higher (BH)max than isotropic magnets, which can be magnetised in any direction but with lower performance.
Temperature grade (N/M/H/SH/UH/EH)
耐温牌号（N/M/H/SH/UH/EH）- NdFeB suffixes that grade the maximum operating temperature and Hcj: N ≤ 80 °C, M ≤ 100 °C, H ≤ 120 °C, SH ≤ 150 °C, UH ≤ 180 °C, EH ≤ 200 °C. Selecting the right grade prevents irreversible demagnetisation in motors and high-temperature assemblies.
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Magnet materials
NdFeB (neodymium-iron-boron)
钕铁硼（NdFeB）- The strongest commercial permanent magnet material. Ternary alloy Nd₂Fe₁₄B with the highest (BH)max and room-temperature performance, used in EV traction motors, sensors, hard drives, audio devices and industrial assemblies. Produced as sintered, bonded, hot-pressed and flexible forms.
Sintered NdFeB
烧结钕铁硼- Powder metallurgy NdFeB: powder pressed in a magnetic field, sintered, machined and coated. Delivers the highest (BH)max (up to N52) but is brittle and oxidation-sensitive, requiring a protective coating (NiCuNi, zinc, epoxy, parylene).
Bonded NdFeB
粘结钕铁硼- NdFeB powder mixed with a polymer (epoxy, nylon, PPS) and injection- or compression-moulded into complex shapes with tight tolerances. Lower (BH)max than sintered but enables intricate geometries and isotropic or anisotropic magnetisation.
Hot-pressed NdFeB
热压钕铁硼- Hot-deformed NdFeB produced by pressing MQ powder at high temperature, yielding anisotropic magnets without heavy rare earths. Combines high Hcj with near-net-shape radial rings for precision motor rotors and sensors.
Samarium cobalt (SmCo)
钐钴（SmCo）- Rare-earth permanent magnet (SmCo₅ or Sm₂Co₁₇) with excellent temperature stability (up to 250–350 °C), high corrosion resistance and low temperature coefficient. Used in aerospace, automotive sensors, instrumentation and any application where NdFeB's temperature limit is insufficient.
Samarium iron nitrogen (SmFeN)
钐铁氮（SmFeN）- Fourth-generation rare-earth magnet (Sm₂Fe₁₇N₃) with high Curie temperature (~470 °C) and strong corrosion resistance. Manufactured as bonded or injection-moulded magnets for wearable, magnetic-health and consumer-electronics applications where oxidation and skin contact matter.
AlNiCo
铝镍钴（AlNiCo）- Early permanent-magnet alloy of aluminium, nickel, cobalt and iron. Excellent temperature stability (up to ~500 °C) and corrosion resistance but low Hcj, so it is easily demagnetised by external fields. Used in instruments, sensors, holding magnets and high-temperature devices.
Ferrite (ceramic) magnet
铁氧体（陶瓷）磁体- Sintered oxide magnet (Ba/SrFe₁₂O₁₉) with low (BH)max but very low cost, high corrosion resistance and no rare-earth content. The default choice for high-volume, cost-sensitive applications: speakers, motors, magnetic chucks, fridge magnets.
Flexible magnet
柔性磁体- Bonded ferrite or NdFeB powder in a flexible rubber or plastic binder, extruded or rolled into sheets, strips and profiles. Easily cut, bent and adhesive-applied for seals, latches, signage, door gaskets and curved-surface applications.
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Processes & treatment
Grain boundary diffusion (GBD)
晶界扩散（GBD）- A process that introduces Dy or Tb only along NdFeB grain boundaries, raising Hcj while using far less heavy rare earth than conventional alloying. It is the basis of low-Dy / heavy-rare-earth-free high-coercivity NdFeB grades.
Heavy rare earth (HRE)
重稀土（HRE）- Dysprosium (Dy) and terbium (Tb), added to NdFeB to raise Hcj for high-temperature grades. Supply and price are volatile, so heavy-rare-earth-free (HRE-free) and GBD technologies are increasingly used to reduce dependence.
Magnet coating / plating
磁体镀层- Protective surface treatment on NdFeB to prevent oxidation and corrosion. Common options: NiCuNi (multi-layer nickel), zinc, epoxy, parylene, Al-ion-plating, passivation. Coating choice depends on environment, temperature and automotive (IATF 16949) requirements.
Magnetisation direction
充磁方向- The direction along which a magnet is magnetised by an external field after shaping. Common patterns: axial, diametral, radial, multipole (N-S-N-S... around the circumference), Halbach. Correct pattern is essential for motors, encoders and sensors.
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Components & devices
Halbach array
海尔贝克阵列（Halbach 阵列）- An arrangement of permanent magnets that rotates the magnetisation direction by 90° from one block to the next, concentrating flux on one side while nearly cancelling it on the other. Used to strengthen the field in motors, maglev, particle accelerators and magnetic chucks without adding material.
Magnetic circuit
磁路- The closed path that magnetic flux follows through a magnet, soft-magnetic pole pieces, air gaps and back-iron. Designing this path — balancing flux density, leakage and reluctance — is magnetic circuit design, the core engineering service that turns a magnet into a working device.
Magnetic encoder
磁性编码器- A position sensor that reads a multi-pole magnetic scale or ring with a Hall or magnetoresistive sensor to measure angular or linear displacement. Robust to dust, oil and vibration where optical encoders fail; standard in servomotors, robotics and automotive actuators.
Magnetic scale
磁栅尺- A linear or rotary ruler carrying a precisely pitched multi-pole magnetisation pattern (e.g. 1 mm, 5 mm pole pitch). Read by a magnetic sensor head to provide absolute or incremental position feedback in machine tools and automation.
Magnetic coupler (coupling)
磁力联轴器- A torque-transmitting device with two magnet rings separated by a non-magnetic containment shell. Transmits torque through the wall of a sealed vessel with no physical contact, enabling hermetic pumps, mixers and vessels for hazardous, sterile or high-purity fluids.
Hall-effect sensor magnet
霍尔传感器磁体- A precision magnet (disc, ring or multi-pole) paired with a Hall-effect IC to detect position, speed, current or field. Magnet geometry, grade and magnetisation pattern are tuned to the IC's sensing range so the output is linear and stable across temperature.
Permanent magnet motor rotor
永磁电机转子- The rotating assembly inside a BLDC, PMSM, servo or traction motor, carrying permanent magnets in surface-mount, interior (IPM) or Halbach configurations. Magnet grade, segmentation and skewing determine efficiency, cogging torque and field-weakening performance.
Magnetic gear
磁力齿轮- A contactless gear that transmits torque between input and output rotors via interacting magnetic pole pairs, achieving a fixed gear ratio without meshing teeth. Provides overload protection, zero backlash, low noise and hermetic isolation — used in precision drives, pumps and cleanroom equipment.
Magnetic filtration
磁过滤- Removal of ferrous particles from coolants, lubricants, slurries or process liquids using high-gradient magnetic filters, grids or tubes. Captures particles below the size that conventional filters can catch, extending fluid life and protecting downstream equipment.
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