Magnetic precursor effects, electrical and magnetoresistance anomalies, and heat-capacity behavior of Gd alloys

The electrical resistivity (rho), magnetoresistance (Delta rho/rho), beat capacity (C), and magnetization (M) behavior in a number of Gd alloys are reported. Particular attention is paid to the rho and Delta rho/rho behavior at temperatures just above respective long-range magnetic ordering temperatures (T-0). In some compounds, e.g., GdNi2Sn2 and GdPt2Ge2, there is an enhancement of rho prior to long-range magnetic order over a wide temperature range which can be highlighted by the suppression of rho caused by the application of a magnetic field. However, such features are absent in many other Gd compounds, e.g., GdCu2Ge2, GdAg2Si2,GdAu2Si2, GdPd2Ge2, and GdCo2Si2. Attempts to relate these features to magnetic precursor effects in C are made. We observe interesting features in the C data, like shoulders and additional transitions in the magnetically ordered state and peak values of C at T-0 varying from one compound to the other. The implications of these observations are discussed. In addition, various Delta rho/rho anomalies, including large positive values at low temperatures in some cases, and the sensitivity of magnetoresistance to held-induced magnetic transitions in comparison with the isothermal M data, are also brought out. [S0163-1829(98)03438-9].