Magnetic Properties of Antiferromagnetic GdAlO3

Abstract

Specific‐heat and magnetic‐susceptibility measurements on GdAlO₃ show that it undergoes a transition to antiferromagnetism at 3.69°K. Magnetization measurements on a single crystal at temperatures down to 0.6°K in fields up to 70 kOe show that the ordered state is a simple two‐sublattice structure with the orthorhombic b axis as the axis of alignment. The spin flop, exchange, and anisotropy fields have been found to be 11.2 kOe, 20 kOe to 25 kOe, and 2.3 kOe to 3.0 kOe, respectively. No parasitic ferromagnetism is observed. Optical absorption studies of Er³⁺ and Dy³⁺ in GdAlO₃ observe the spin flop and confirm that in the ordered structure the distorted simple cubic lattice of Gd³⁺ ions divides into two sublattices with each ion surrounded by six nearest neighbors belonging to the opposite sublattice.