magnet

A magnet is an object that produces a magnetic field and exerts forces on other magnets or magnetic materials. Some materials are naturally magnetic, such as lodestone, but magnets are often manufactured from alloys such as iron, nickel, cobalt, or specialized permanent magnets like NdFeB and SmCo.

Magnetic fields arise from moving electric charges and electron spin. In permanent magnets, microscopic regions called domains realign during magnetization, giving rise to a net magnetic moment. When heated above the Curie temperature or exposed to strong opposing fields, magnets can lose their magnetization.

Magnetic poles are conventionally described as north and south; like poles repel and opposite poles attract. Magnetic fields form dipole patterns around magnets and extend into surrounding space, influencing magnetic materials.

Key properties of magnets include remanent magnetization (residual magnetization after external field is removed), coercivity (resistance to demagnetization), and saturation magnetization. Materials are classified as ferromagnetic (highly responsive), paramagnetic, or diamagnetic.

Common applications span navigation (compasses), electric machines (motors, generators), transformers and inductors, magnetic storage (hard disks, tape), medical imaging (MRI), and magnetic separation techniques. Magnetic materials enable data to be stored as magnetized regions corresponding to binary information.

The Earth's magnetic field originates in convection and spin in the outer core, creating a giant natural magnet. Strong magnets can pose hazards due to attraction to ferrous objects.