The negative volume magnetostriction of GdAl2 with a cubic Laves structure

Spontaneous volume magnetostriction of the intermetallic compound GdAl2 is studied from the X-ray diffraction measurement at low temperature. It was found that GdAl2exhibits the ferromagnetic transition at TC ∼170 K without lowering of crystal symmetry of a cubic C15 Laves structure. The temperature dependence of the lattice constant a is in good agreement with that of the volume thermal expansion, in which negative spontaneous volume magnetostriction has been observed. It indicates that the magnetic exchange interaction can be described by the distance between the Gd moments. From these experimental results, the origin of the negative magnetostriction is discussed on the basis of the localized spin model of ferromagnetism.