Low-temperature properties of the Yb-based heavy-fermion antiferromagnets YbPtIn, YbRhSn, and YbNiGa

The crystallographic and low-temperature properties of the equiatomic Yb-ba sed compounds YbPtIn, YbRhSn (hexagonal ZrNiAl structure), and YbNiGa (orth orhombic epsilon-TiNiSi structure) are studied by means of x-ray diffractio n, magnetic susceptibility, magnetization, electrical resistivity (rho), ma gnetoresistance, thermoelectric power, and specific-heat (Cp) measurements. The magnetic susceptibility follows a Curie-Weiss law with effective magne tic moments close to the value of Yb3+ and shows strong magnetocrystalline anisotropy. At low temperature the three compounds exhibit the typical prop erties of antiferromagnetic (AFM) Kondo lattices, namely a logarithmic incr ease of rho(T), enhanced electronic Cp coefficients gamma(0), and a reduced entropy gain below the ordering temperature. The values of gamma(0) > 350 mJ/molK(2) are among the largest of known Yb-based magnetic Kondo lattices. Two AFM transitions in each compound evidence a competition between single -ion anisotropy and frustration of the magnetic interactions due to the top ology of the underlying crystal structure. The ground-state properties are discussed and compared with those of other f-electron compounds showing sim ilar characteristics concerning magnetic frustration.