Magnetic and Transport Properties of Single-Crystal YbPtGe

Abstract

The magnetic and transport properties of single-crystal YbPtGe with the TiNiSi-type orthorhombic structure are presented. It is revealed that YbPtGe is a ferromagnet with T C = 5.4 K. Although both of its paramagnetic and ferromagnetic states show uniaxial anisotropy, its easy axis changes from the a -axis in the paramagnetic state to the c -axis below T C . Magnetizations at 2 K along the a -, b -, and c -axes saturate to constant values of 1.5 µ B for 6 kOe, 0.55 µ B for 2 kOe, and 1.1 µ B for 1 kOe, respectively. The magnetic contribution to the specific heat shows a Schottky anomaly centered at 90 K due to the crystalline electric field (CEF) effect that splits the eight-hold J -multiplet of the Yb 3+ ion into four doublets. The Sommerfeld coefficient γ is estimated to be 209 mJ/(mol·K 2 ) below T C . The magnetic entropy released up to T C is 52% of that of R ln 2, expected for the doublet ground state. Therefore, YbPtGe is a middle-classed heavy-fermion compound with a ferromagnetic transition.