Hard Magnetic Materials
Magnetic materials can produce magnetic fields, which generate forces attracting or repelling ferromagnetic materials and other magnets. Magnetic material can be divided into soft and hard magnets. Soft magnets are those materials easy to magnetize and demagnetize, while hard magnets are difficult to do so and retain strong magnetism after the removal of applied magnetic field. Hard magnets are also called permanent magnets, which include Neodymium magnets, SmCo magnets, AlNiCo magnets and Ferrite magnets. As neodymium and samarium are rare earth elements, Neodymium magnets and SmCo magnets form rare earth permanent magnets.
Magnetic material exist in nature in a fascinating way as the earth we live on is a huge magnet itself. Ongoing research and innovation in the field has advanced the developments of a variety of magnetic materials, which play an increasingly important role in our modern life and industrial world. The applications of magnetic materials cover a broad span of areas, such as aerospace, transportation, information technology, industrial automation, consumer electronics, medical devices and clean energy.
Sintered Neodymium Magnets
Sintered neodymium magnet is the strongest magnetic material commercially available today. It is largely made of alloy of neodymium, iron and boron, and the chemical formula is Nd2Fe14B. Sintered NdFeB neodymium magnet exhibits high magnetic energy product in small size with high coercive forces. Examples of applications include permanent magnet motors, loudspeakers, magnetic separators, wind power generators, computer hard drive, and MRI devices.
Hot Pressed Neodymium Magnets
Hot pressed neodymium magnets include hot-pressed isotropic NdFeB magnets and hot-extruded anisotropic NdFeB magnets, which have high magnetic energy product and high coercive forces with precise tolerance. The hot-extruded anisotropic NdFeB magnet is particular good for the manufacture of radial ring magnets of small size with high magnetic performance requirements.
Bonded Neodymium Magnets
Bonded neodymium magnets can be pressed or extruded in complex forms, and magnetized into different patterns with multiple poles. It gives greater flexibility over shapes can be made and enables high precision for small sizes. Typical applications include sensors, brushless DC motors, stepper motors and actuators.
Samarium cobalt magnets exist in two alloy varieties, SmCo5 being the original and Sm2Co17 being the more commonly used. Samarium cobalt magnets have excellent magnetic stability, very low temperature coefficient, and superior corrosion resistance. It is often used in high temperature applications and poor working environments with high magnetic performance requirements.
AlNiCo magnets are manufactured by either casting or sintering process. Aluminum nickel cobalt magnet is the permanent magnet material with the highest curie temperature. Cast magnet can be produced in complex shapes with low cost. AlNiCo magnet has low coercive force, and is easily demagnetized if not handled properly.
Ferrite magnets can be produced through sintering and injection molding. They have good resistance to demagnetization, and enjoy cost advantage with relatively low magnetic performance. Injection molded ferrite magnets incur higher tooling cost, and can be made into intricate shapes with tight tolerances. Ferrite magnets are widely used in motors, consumer electronics, household appliances, information and communication products, and consumer goods.
Increasingly Extensive Demand of Hard Magnetic Materials Application
Permanent magnetic materials, also known as hard magnetic materials, are materials that still have magnetism after the magnetization field is removed. Soft magnetic materials have strong magnetic induction strength when the magnetization field exists, and lose magnetism when the magnetization field is removed. Hard and soft here do not mean hard and soft in mechanical properties, but in magnetic properties. Hard magnetism means that a magnetic material can retain its strong magnetism (magnetism for short) for a long time after being magnetized by an external magnetic field, and is characterized by strong coercivity. Coercivity is the magnetic field strength that makes magnetized materials undergo demagnetization and reduce the residual magnetism (residual magnetic flux density or residual magnetization) to zero.
At present, the application market of magnetic materials products in China is expanding rapidly. Magnetic materials matching components are increasingly demanded in the domestic market. In accordance with the requirements of environmental protection, oil-free automobiles and motorcycles are the direction of future development, which will bring a broad market to the development of rare earth permanent magnets. “Green Lighting Project” is also a major energy-saving project in our country. The development of energy-saving lamps requires the use of a large number of high-end ferrite soft magnetic cores and anti-interference magnetic cores.
With the increasing number of car production and speakers used, the demand for ferrite permanent magnet materials is also increasing. The development of computers has driven the development of related supporting components. Magnetic disks, optical disk drives and printer drive heads are the largest “users” of NdFeB. Multimedia acoustics also demands permanent magnetic materials (hard magnetic materials) in a large amount.