The rare earth
magnetic material is new type metal permanent magnetic material which appeared in the 1960s, it is an alloy that composed of rare earth metal elements(samarium, Neodymium mixture rare-earth metal) and excessive metal(such as cobalt, iron).And it is made out by pressing and sintering of powder metallurgy method, then magnetized in a magnetic field. Along with the developing of computer and communication industry,r are earth permanent magnets get rapidly develop,e specially NdFeB magnets industry.
Rare earth permanent magnetic material is metallic compound, which composed of different rare-earth elements and excessive metal elements (Fe, Co,Ni etc), and it is new type permanent magnetic material that got rapid development during the nearest 20 years.
Rare earth magnets developed very speedily , it is now widely used in many fields, and become to be an important material basis for contemporary technique. samarium-cobalt alloys were used to produce rare-earth permanent motors since the 1980s, the product including a servo motor, drive motor, auto starter, military motor, aero motor etc, part of them was sold for export.
Rare earth magnets not only have high remanence strength and high maximum energy product but also have very high coercivity. This is no any permanent magnetic materials can be compared with it. So far, the coercivity of sintered cobalt basis rare earth permanent magnets can be up to 800KA/m, and the coercivity of sintered iron-based rare earth permanent magnets can be up to 850KA/m.
In the visible, rare earth permanent magnets have below performance advantages:
(1) High magnetic property: have very high remanence intensity(B), high maximum energy(B.H) and high coercivity especially intrinsic coercive force. The remanence strength of sintered cobalt-based rare earth permanent magnets is up to 1.2T, which is close to the highest value of AlNiCo permanent magnets, and coercive force can be up to 800kA/m which is about 3 times of the value for ferrite permanent magnets.
(2) straight demagnetization characteristic: its demagnetization curve is an almost straight line. The recovery line coincides with demagnetization curve, the reversible magnetic inductivity is close to 1.0.
(3)High-temperature resistance: the Curie temperature of for sintered cobalt based rare earth magnets can be up to 850, so it suits for high working temperature, the working temperature is about 300 ℃.
(4)Temperature stability is better: reversible temperature coefficient of remanence strength for cobalt based permanent magnets can be made to 0.03%, which is close to the value of AlNiCo permanent magnets.
