MAGNETIC PRECURSOR EFFECTS, ELECTRICAL AND MAGNETORESISTANCE ANOMALIES, AND HEAT-CAPACITY BEHAVIOR OF GD ALLOYS

The electrical resistivity (rho), magnetoresistance (Delta rho/rho), b eat capacity (C), and magnetization (M) behavior in a number of Gd all oys are reported. Particular attention is paid to the rho and Delta rh o/rho behavior at temperatures just above respective long-range magnet ic 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 su ppression of rho caused by the application of a magnetic field. Howeve r, 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 inter esting features in the C data, like shoulders and additional transitio ns in the magnetically ordered state and peak values of C at T-0 varyi ng from one compound to the other. The implications of these observati ons are discussed. In addition, various Delta rho/rho anomalies, inclu ding 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].