INVAR PROPERTIES IN THE RARE EARTH-3D TRANSITION-METAL ALLOYS

The RCo2 and R2Fe17 compounds (R = rare earth) exhibit Invar-like thermal expansion anomalies below their ordering temperatures. These spontaneous volume magnetostrictions are discussed by considering their magnetic properties. In RCo2 compounds there is no intrisinc Co-moment is induced by the exchange and applied fields. The volume expansion anomaly is associated with the onset of the 3d magnetic moment. IN R2Fe17 compounds there is an intrisinc Fe- moment. Magnetic structures give evidence for positive and negative exchange interactions between Fe atoms which are strongly distance dependent. The thermal expansion anomaly is a result of this distance of the magnetic interactions. © 1979.