In our rapidly advancing technological landscape, magnetic materials serve as crucial functional components across industries including manufacturing, healthcare, electronics, and energy. Among these, neodymium iron boron (NdFeB) permanent magnets, commonly called neodymium magnets, reign supreme with their exceptional magnetic properties such as high energy product and coercivity, earning them the title "King of Magnets." However, their extraordinary strength also presents significant safety challenges. This report provides an in-depth examination of neodymium magnets' magnetic properties, applications, safety risks, and future development trends, offering comprehensive technical guidance and safety recommendations for researchers, engineers, and the general public.

Magnetic materials can generate magnetic fields or respond to external magnetic fields. They are classified into permanent magnets (retaining magnetism after magnetization) and soft magnets (easily magnetized and demagnetized).

Magnetism originates from electron motion within materials. Both electron spin and orbital movement generate magnetic moments, whose arrangement determines material magnetism:

• Paramagnetism: Random magnetic moment alignment produces weak magnetization under external fields that disappears when removed.
• Diamagnetism: Electron orbital motion induces opposing magnetic moments under external fields.
• Ferromagnetism: Spontaneous magnetization domains with aligned moments produce strong magnetism.
• Ferrimagnetism: Unequal opposing magnetic moments from different ions create net magnetism.
• Antiferromagnetism: Equal opposing magnetic moments result in zero net magnetism.

Neodymium magnets belong to rare-earth permanent magnets, primarily composed of neodymium (Nd), iron (Fe), and boron (B). Their exceptional performance stems from unique crystal and electronic structures:

Neodymium magnets feature a tetragonal crystal system with high magnetocrystalline anisotropy, meaning preferred magnetization directions along specific crystal axes (typically the c-axis).

Neodymium's unfilled 4f electron shell generates substantial magnetic moments, while iron contributes additional moments. Strong exchange interactions between these elements create ordered magnetic alignment, with boron stabilizing the crystal structure.

Key parameters characterize neodymium magnets:

• Remanence (Br): Residual magnetic induction after external field removal.
• Coercivity (Hcb): Reverse field strength required to demagnetize.
• Intrinsic Coercivity (Hcj): Field strength to reduce magnetic polarization to zero.
• Maximum Energy Product (BH)max: Peak value of B×H product on demagnetization curve.
• Curie Temperature (Tc): Temperature at which magnetism is lost.

Neodymium magnets are graded by energy product (e.g., N35-N52), with higher numbers indicating stronger magnetism. Suffixes denote temperature resistance (SH=150°C, UH=180°C, EH=200°C).

Gaussmeters or teslameters measure magnetic fields using Hall or magnetoresistance effects:

Voltage generated perpendicular to current and field directions, proportional to field strength.

Material resistivity changes under magnetic fields.

Note: Actual performance depends on shape, size, grade, temperature, and environment.

• Motors/Generators: Enhance efficiency and power density in servos, wind turbines, etc.
• Sensors: Improve sensitivity in position/speed detectors.
• Magnetic Couplings: Enable contactless power transmission.

• MRI Systems: Generate strong imaging fields.
• Therapeutic Devices: Used in pain-relief applications.

• Audio Equipment: Critical for high-quality speakers and headphones.
• Microphones: Boost sensitivity and signal clarity.

• Toys/Stationery: Enable innovative designs in magnetic puzzles and tools.
• Jewelry: Combine fashion with potential therapeutic benefits.

Powerful attraction forces can cause severe injuries. Protective measures include using tools, gloves, and isolation protocols for large magnets.

Strong fields may disrupt devices like phones and credit cards. Maintain safe distances or implement shielding.

Magnetic fields can interfere with cardiac devices. Warning signs should be posted in public areas.

Small magnets pose intestinal perforation risks if swallowed. Keep away from children and secure in products.

High temperatures degrade magnetic properties. Select appropriate temperature grades and cooling solutions.

Grain boundary diffusion (adding dysprosium/terbium) and nanocrystalline technologies aim to boost coercivity and energy density.

Laser cutting and thin-film deposition enable smaller magnets for microelectronics and medical implants.

Advanced coatings (nickel, epoxy) and alloying (with aluminum/copper) improve durability.

Shortened manufacturing processes and recycling initiatives reduce environmental impact.

Neodymium magnets' unparalleled strength drives technological innovation but demands rigorous safety protocols. Future advancements will focus on optimizing performance while addressing environmental and safety concerns through material science breakthroughs and responsible engineering practices.