Magnets

What Is a Permanent Magnet?

Permanent Magnet Physics Definition

At the atomic level, permanent magnetism arises from the alignment of magnetic domains: microscopic regions where groups of atoms orient their magnetic moments in the same direction. When a sufficient proportion of these domains align through a manufacturing process called "magnetization," the material produces a net external magnetic field strong enough for practical use.

Three key properties define a permanent magnet's performance

Types of Permanent Magnets by Material

In product design, selecting the wrong magnet material is one of the most costly mistakes one can make. The following text provides a structured overview of the three dominant categories of permanent magnets currently available on the market, accompanied by intuitive comparative data, with the aim of offering you robust support during the material selection process.

Neodymium (NdFeB)

GME supplies sintered neodymium (NdFeB) magnets in grades N35–N52, factory-direct with OEM/ODM custom shapes, the world's strongest permanent magnet material.

BHmax Range: 33 – 52 MGOe

Max. Working Temp: 80°C – 200°C

Grades Available: N35–N52, M, H, SH, UH, EH

Coating Required: Yes (NiCuNi / Epoxy)

Applications: EV Motors, Wind Turbines, Robotics

MRI Adjacent, Consumer Electronics.

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Samarium Cobalt (SmCo)

GME manufactures samarium cobalt (SmCo) magnets for aerospace, defense, and downhole applications requiring uncompromising high-temperature performance.

(BHmax) Range: 16 – 32 MGOe

Maximum Operating Temperature: 250°C – 350°C

Available Grades: Sm2Co5, Sm2Co17

Coating Requirement: Typically requires no coating

Applications: Aerospace, Downhole Oil & Gas Exploration, Defense Sensors, Satellite Systems.

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Alnico

GME supplies Alnico magnets by both casting and sintering.

Maximum Energy Product (BHmax) Range: 1.5 – 11 MGOe

Maximum Operating Temperature: 540°C

Temperature Coefficient (Br): -0.02%/°C (Lowest)

Manufacturing Process: Casting or Sintering

Applications: Guitar Pickups, Aerospace Instrumentation, Flow Meters, High-Temperature Sensors.

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How to Choose the Right Permanent Magnet Material

Material selection is the single most critical decision in magnet procurement. The wrong choice costs you in rework, warranty claims, and performance failures. Use this decision matrix

Examples and Industrial Applications of Permanent Magnets

From everyday consumer devices to critical industrial systems, permanent magnets are at the core of how the modern world moves, senses, and generates power.

Smartphone Speakers

NdFeB disc magnets in earpieces convert signals to sound.

Hard Disk Drives

NdFeB arc magnets position read/write heads with nanometer precision.

EV Traction Motors

High-grade NdFeB (SH/UH) arc magnets in rotor assemblies.

Guitar Pickups

Alnico 2/5 for vintage tone; NdFeB for modern high-output.

Refrigerator Door Seals

Flexible ferrite strips maintain an airtight closure without latches.

Headphones & Earbuds

NdFeB drivers deliver a wide frequency response in compact form. 

E-Bike Hub Motors

NdFeB arc magnets for silent, efficient propulsion.

MagSafe / Wireless Charging

NdFeB ring arrays for precise alignment and power transfer.

Magnetic Door Catches

Pot magnets in steel cups provide tool-free secure closure.

Electric Toothbrushes
NdFeB magnets in silent brushless motors.

How Do Permanent Magnets Work? 

Permanent magnets work because their internal magnetic domains are aligned. When these domains point in the same general direction, the material creates a magnetic field around itself. This magnetic field can attract ferromagnetic materials and interact with other magnetic fields.
 

Magnetic Domain Theory and Field Generation

Every atom with unpaired electrons acts as a tiny magnetic dipole, a microscopic bar magnet. In most materials, these atomic dipoles point in random directions and cancel each other out, producing no net magnetic field.

In ferromagnetic materials (iron, nickel, cobalt, and their alloys), quantum mechanical exchange interactions force neighboring atomic moments to align parallel. This alignment forms magnetic domains: regions typically 10–100 micrometers in size where millions of atoms collectively point in the same direction.

Before magnetization: Domains exist, but they point in random directions, with a net external field of zero.

After magnetization: An external field above the material's saturation threshold forces domains to align with the net external field, strong and persistent.

Once aligned, the domain walls cannot easily reverse their orientation due to the material's magnetocrystalline anisotropy. This is what makes NdFeB magnets so powerful: the Nd₂Fe₁₄B crystal structure has exceptionally high anisotropy energy.

Understanding Coercivity, Remanence, and the BH Curve

The BH curve is the fundamental tool for characterizing and comparing permanent magnets. Every magnet datasheet references it.

Comparisons: Permanent Magnets vs. Temporary Magnets vs. Electromagnets

Do Permanent Magnets Lose Their Magnetism Over Time?

This is one of the most common questions from engineers specifying magnets for long-life applications. The short answer: a well-specified permanent magnet, properly handled, will retain >95% of its original flux density for decades, sometimes over 100 years.

The Four Real Causes of Demagnetization

1. Elevated Temperature (Most Common)

Exceeding the maximum working temperature causes partial, potentially irreversible flux loss. Standard N-grade NdFeB has a max of 80°C; EH-grade extends this to 200°C. Always operate at least 30°C below the rated maximum.
2. Opposing Magnetic Fields

External fields opposing the magnet's field and exceeding its intrinsic coercivity (Hci) can partially or fully demagnetize it. This is why high-Hci grades (SH, UH, EH) are critical in motor applications.
3. Physical Shock and Vibration

Severe mechanical impact can jolt domain walls out of alignment. More of a concern for Alnico (lower coercivity) than for NdFeB or SmCo. Handle large magnets (50mm+) with dedicated separation tools.
4. Corrosion (NdFeB Specific)

Uncoated NdFeB in humid or salt-spray environments will corrode and lose magnetic performance. Always specify the correct coating (NiCuNi, Epoxy, Gold) based on your operating environment.

Custom Magnet Shapes & OEM Manufacturing

GME manufactures custom permanent magnets from 2D/3D drawings in any shape, disc, block, ring, arc, countersunk, or fully custom profile.

Shape: Disc / Cylinder Magnet
Typical Applications: Sensors, speakers, medical devices, pot magnets
Available Materials: NdFeB, SmCo, Alnico, Ferrite

Shape: Block / Rectangle Magnet
Applications: Magnetic chucks, holding fixtures, motor assemblies
Available Materials: NdFeB, SmCo, Alnico, Ferrite

Shape: Ring / Annular Magnet
Applications: Bearings, loudspeakers, rotary encoders
Available Materials: NdFeB, SmCo, Ferrite

Shape: Arc / Segment Magnet
Applications: Motor rotors, generator assemblies, wind turbines
Available Materials: NdFeB, SmCo, Ferrite

Shape: Countersunk Magnet
Applications: Mechanical fastening, furniture, fixtures
Available Materials: NdFeB, Ferrite

Shape: Custom Magnet
Applications: Per 2D/3D drawing any shape within material constraints
Available Materials: NdFeB, SmCo

Surface Coating Options

NdFeB magnets require surface protection in most applications. The coating you choose affects corrosion resistance, operating temperature range, electrical conductivity, and cost.

Submit Your Requirements

How to Order Custom Magnets from GME:

Submit your drawing (DXF/STEP/PDF) or describe your requirements.
Receive material recommendation + DFM feedback within 24h.
Approve sample - production in 15-30 days.

Quality Assurance: Testing and Compliance Standards

GME's in-house QA lab tests every production batch against IEC 60404-5 (coercivity), IEC 60404-8-1 (remanence), and ASTM A977 (BHmax). Coating reliability is verified by ISO 9227 salt spray testing (24–200h depending on coating type) and ISO 2409 adhesion cross-cut. All dimensional data is logged to ±0.05mm tolerance. ISO 9001:2008 certified. CE and RoHS documentation available for every standard product line.

In-Process Quality Controls

Every production batch at our Xiamen facility goes through a documented, multi-stage quality control process, not just a final inspection.

Raw Material Verification Every incoming NdFeB and SmCo alloy batch is verified by XRF composition analysis before it enters production. Particle size distribution and density are measured post-sintering to confirm the batch meets grade specification before magnetization.

Magnetic Performance Testing. This is where most suppliers cut corners. GME tests every production batch, not just samples, against the following parameters:

Coating & Reliability Testing: A magnet that tests well magnetically but fails in the field due to coating delamination is still a defective product. GME applies the following coating verification tests:

Salt Spray Test

Coating Adhesion Test

Thermal Cycling Test

High Humidity Test

Certifications Overview

CE

RoHS Test Report

SGS

ISO 14001:2004

ISO 9001:2008

Safety Handling and Shipping Guidelines for Strong Magnets

"Strong magnets, especially neodymium, require careful handling and proper storage to ensure safety for both personnel and equipment.

How to Safely Handle Powerful Neodymium Magnets

Strong NdFeB magnets are capable of causing serious injury and equipment damage. The following guidelines are mandatory for safe handling:

Personal Protection:

✅ Always wear leather

cards, hard drives, and magnetic media (permanent data loss risk).

Separation and Handling Technician gloves, magnet chips are sharp and can lacerate skin.

✅ Wear eye protection when separating magnets above N45 grade or above 50mm size.

✅ Keep magnets away from pacemakers, cochlear implants, and other electronic medical devices (minimum 30cm).

✅ Keep away from credit cards, hard drives, and magnetic media (permanent data loss risk).

Separation and Handling Technique:

❌ Never allow two strong magnets to snap together. The impact can shatter the magnets and send fragments at high velocity.

✅ Sliding magnets apart rather than pulling directly requires significantly less force and prevents snapping.

✅ For magnets above 80mm: use dedicated separator tools or hardwood wedges; never use bare hands.

✅ Store magnets with cardboard or plastic spacers between units and in individually labeled bags or trays.

Environmental Storage:

Keep in a dry, temperature-controlled environment (10–30°C, <60% RH).

Do not store near strong opposing magnetic fields or large ferromagnetic structures.

Keep NdFeB magnets in their original anti-corrosion packaging until the point of use.

Great Magtech (Xiamen) Electric Co., Ltd is one of the most experienced magnets manufacturers and suppliers in China. Welcome to wholesale magnets from our factory.