Giant Uniaxial Anisotropy in the Magnetic and Transport Properties of CePd5Al2
Abstract
Electrical resistivity rho, magnetic susceptibility chi, magnetization M and specific heat measurements are reported on a singlecrystalline sample of CePd5Al2, showing successive antiferromagnetic orderings at TN1=4.1 K and TN2=2.9 K. The temperature dependence of TN1 shows a Kondo metal behavior with large anisotropy, rhoc/rhoa=3.2 at 20 K, and opening of a superzone gap along the tetragona c-direction below TN1. Both TN1 and TN2 gradually increase with applying pressure up to 2.5 GPa. The data of chi(T) and M(B) in the paramagnetic state were analyzed using a crystalline electric field (CEF) model. It led to a Kramers doublet ground state with wave functions consisting primarily of |+-5/2>, whose energy level is isolated from the excited states by 230 and 300 K. This CEF effect gives rise to the large anisotropy in the paramagnetic state. In the ordered state, the uniaxial magnetic anisotropy is manifested as Mc/Ma=20 in B=5 T and at 1.9 K, and chic/chia=25 in B=0.1 T and at 4 K. This huge uniaxial magnetic anisotropy in the antiferromagnetic states can be interpreted in terms of isotropic magnetic interaction among the Ce3+ moments governed by the strong CEF. In powder neutron diffraction experiments, magnetic reflections were observed owing to the antiferromagnetic ordered states below TN1, however, no additional reflection was found below TN2.