The hard-magnetic properties of rare earth-transition metal alloys

The intermetallic phases formed between the rare earth metals (R) and the elements of the 3-d transition series are a large group of new substances with interesting magnetic properties. They have been studied intensely in the last decade. Their properties are reviewed with a view toward their usefulness for permanent magnets. Some aspects of the recently developed magnets based on certain RCo5compounds are discussed. The prediction is made that second-generation rare earth magnets can be developed using R2(Co,Fe)17alloys. These should have energy products and thermal stability superior even to sintered SmCo5, while being less expensive. Experimental evidence supporting this claim is discussed.