Magnetic precursor effects in Gd alloys

The behaviour of electrical resistivity ($\rho$) and magnetoresistance in the vicinity of respective magnetic ordering temperatures in a number of Gd alloys is reported. In some compounds, e.g., GdNi_2Sn_2 and GdPt_2Ge_2, 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., GdCu_2Ge_2, GdAg_2Si_2, GdAu_2Si_2, GdPd_2Ge_2 and GdCo_2Si_2. Attempts to relate such features to magnetic precursor effects in heat capacity are made. On the basis of our studies, we suggest that better understanding of magnetic precursor effects in Gd alloys will be helpful to throw light on some of the current trends in magnetism. Various other interesting findings in the magnetically ordered state in some of these alloys are also brought out.