Magnetotransport Properties of Heavy-Fermion Ferromagnet YbPtGe

The transverse magnetoresistivity rho(H), Hall coefficient R-H, and specific heat C for H parallel to a below 10 kOe for the moderate heavy-fermion ferromagnet YbPtGe with the Curie-temperature T-C = 5.4 K are reported. It is observed that the rho(H)(T) values for the currents along the three crystallographic axes markedly decrease below 30 K with increasing applied magnetic field up to 90 kOe. Below T-C, rho(H)(H) at low fields show peak structures for H parallel to a and H parallel to b, and a shoulder for H parallel to c, the positions of which correspond to those of shoulders that observed in the field dependence of the magnetization. The sharp peak of C(T) due to magnetic transition decays and shifts to the low-temperature side with increasing field for H parallel to a up to 3 kOe. The H-T phase diagram below T-C is proposed from those measurements. In addition, R-H(T) for I parallel to b and H parallel to c at 10 kOe increases from a value close to the expected Hall coefficient for a carrier concentration of 1 hole/f.u. with decreasing temperature from 300 K, and shows a peak at 8 K. By the application of a magnetic field, this peak decays and shifts to higher temperatures. R-H(T, H) for I parallel to b and H parallel to a is similar to that for I parallel to b and H parallel to c. These peaks of R-H(T) are ascribed to the extraordinary Hall effect due to the skew scattering of conduction carriers.