Magnetic and thermodynamic properties of Nd T2Ge 2 ( T=Pd, Ag) compounds

Abstract

Physical properties of NdPd 2Ge 2 and NdAg 2Ge 2, crystallizing with the tetragonal ThCr 2Si 2-type crystal structure, were investigated by means of magnetic, calorimetric, electrical transport as well as by neutron diffraction measurements. The specific heat studies and neutron diffraction measurements were performed down to 0.30 K and 0.47 K, respectively. Both compounds exhibit antiferromagnetic ordering below T N equal to 1.5 K for NdPd 2Ge 2 and 1.8 K for NdAg 2Ge 2. Neutron diffraction data for the latter germanide indicate antiferromagnetic collinear structure described by the propagation vector k =(0.5, 0, 0.5). The Nd magnetic moments equal to 2.24(5) μ B at 0.47 K are aligned along the a-axis and have the +− sequence within the crystal unit cell. For NdPd 2Ge 2 only very small Bragg peaks of magnetic origin were observed in the neutron diffraction patterns measured below T N, thus hampering determination of the magnetic structure. Both compounds exhibit metallic-like electrical conduction. From the specific heat data the crystal electric field (CEF) levels schemes were determined. Difference between the overall CEF splitting in the two compounds is correlated with their structural parameters.