Types of magnets: Shape magnets: square magnets, tile magnets, special-shaped magnets, cylindrical magnets, ring magnets, wafer magnets, bar magnets, magnetic frame magnets, attribute magnets: samarium cobalt magnets, ferrite magnets, AlNiCo magnets, FeCrCo magnets, industrial magnets: magnetic components, motor magnets, rubber magnets, plastic magnets, etc. Magnets are divided into permanent magnets and soft magnets. Permanent magnets are combined with strong magnetism, so that the spin of magnetic substances and electron angular momentum are arranged in a fixed direction. Soft magnetism is the addition of electricity. When the current is removed, the soft iron will gradually lose its magnetism. Magnetic materials have also been widely used in the military field. For example, ordinary mines or mines can only explode on contact with the target, and thus have limited effect. And if sensor magnets are installed on mines or mines, since tanks or warships are made of steel, when they are close (without touching the target), the sensors can detect changes in the magnetic field and cause the mines or mines to explode, increasing the lethality.
A neodymium magnet (also known as NdFeB, NIB or Neo magnet) is the most widely used type of rare-earth magnet. It is a permanent magnet made from an alloy of neodymium, iron, and boron to form the Nd2Fe14B tetragonal crystalline structure. Developed independently in 1984 by General Motors and Sumitomo Special metals, neodymium magnets are the strongest type of permanent magnet commercially available. Because of different manufacturing processes, they are divided into two subcategories, namely sintered NdFeB magnets and bonded NdFeB magnets. They have replaced other types of magnets in many applications in modern products that require strong permanent magnets, such as electric motors in cordless tools, hard disk drives and magnetic fasteners. Neodymium is a metal that is magnetic, specifically it has antiferromagnetic properties, however in pure form its magnetic properties only appear at low temperatures, below 19 K (−425.5 °F). However, some compounds of neodymium with transition metals such as iron are ferromagnetic, with Curie temperatures well above room temperature, and these are used to make neodymium magnets. The strength of neodymium magnets is the result of several factors. The most important is that the tetragonal Nd2Fe14B crystal structure has exceptionally high uniaxial magnetocrystalline anisotropy (HA ≈ 7 T – magnetic field strength H in units of A/m versus magnetic moment in A·m2). This means a crystal of the material preferentially magnetizes along a specific crystal axis but is very difficult to magnetize in other directions. Like other magnets, the neodymium magnet alloy is composed of microcrystalline grains which are aligned in a powerful magnetic field during manufacture so their magnetic axes all point in the same direction. The resistance of the crystal lattice to turning its direction of magnetization gives the compound a very high coercivity, or resistance to being demagnetized.
