Giant Uniaxial Anisotropy in the Magnetic and Transport Properties of CePd5Al2

TL;DR

This study reports on the anisotropic magnetic and transport properties of CePd5Al2, revealing successive antiferromagnetic orderings, strong uniaxial anisotropy driven by crystal electric field effects, and pressure-dependent magnetic transitions.

Contribution

It provides detailed experimental analysis of CePd5Al2's magnetic anisotropy and ordering, highlighting the role of CEF effects in uniaxial anisotropy and pressure effects on magnetic transitions.

Findings

Successive antiferromagnetic transitions at 4.1 K and 2.9 K.

Large uniaxial magnetic anisotropy with M_c/M_a=20.

Pressure increases T_N1 and T_N2 up to 2.5 GPa.

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 T_N1=4.1 K and T_N2=2.9 K. The temperature dependence of T_N1 shows a Kondo metal behavior with large anisotropy, rho_c/rho_a=3.2 at 20 K, and opening of a superzone gap along the tetragona c-direction below T_N1. Both T_N1 and T_N2 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 M_c/M_a=20 in B=5 T and at 1.9 K, and chi_c/chi_a=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 Ce^{3+} moments governed by the strong CEF. In powder neutron diffraction experiments, magnetic reflections were observed owing to the antiferromagnetic ordered states below T_N1, however, no additional reflection was found below T_N2.