Magnetic and thermal studies on ErCo2–ErAl2

Abstract

Details of the magnetization behavior of the pseudobinary system ErCo2–ErAl2 at temperatures from 1.6 to about 70 K are presented and compared with previous neutron diffraction experiments. ErCo2 shows a first‐order phase transition at 33 K from ferrimagnetic order to paramagnetism. Replacement of Co by Al destroys this unusual feature and initially results in enhanced magnetic exchange with increasing ordering temperatures, although the Co moment is rapidly decreasing due to electron transfer. The moment on Co sites is completely quenched beyond 30 mole% ErAl2. Disordered magnetic components on Er sites which develop in the pseudobinary region and have been identified with neutrons can be partly forced into the field direction, but the saturation values are limited by the anisotropy. The origin of disorder is discussed as being either a consequence of the disorder on crystallographic sites or of the changing valence electron concentration. Differential thermal analysis shows only the onset of magnetic ordering and no signs of subsequent magnetic transitions at lower temperatures (down to 4.2 K) for materials with only partial magnetic order.