Magnetism of PrPtAl

Abstract

Recently Kitazawa et al. have found experimentally that the Van Vleck paramagnet PrPtAl shows canted order below 5.8 K. Paying attention to the crystal structure we study theorerically its magnetic properties. PrPtAl takes orthorhombic structure with space group Pnma. There exist four units of PrPtAl in the unit cell. The crystalline electric field (CEF) at one Pr ion is related to those at other three Pr ions by inversion and mirror reflection, respectively. Thus the Van Vleck susceptibility tensors for four sites are classified into two groups and their principal axes become the mirror reflection of another. The magnetization which tends to align along the easy axes of the Van Vleck susceptibility tensor at each sites is forced by the isotropic exchange interaction and then canted magnetic order can occur. On the basis of a simplified CEF Hamiltonian, mean field calculation is done, which reproduces some charactaristics of the experimental results.