Anomalous magnetoresistance near the spin reorientation transition of dilute Gd-Y single crystals

We report very detailed measurements of the magnetoresistance (MR) in the vicinity (+/-5 K) of the spin reorientation temperature (T-SR) for pure Gd and Gd1-xYx single crystals with x = 0.025 and 0.075. The temperature dependence of the a-axis magnetoresistance in pure Gd is always negative in the temperature range studied. In the dilute Gd - Y samples the low-field MR changes from negative above T-SR to positive for T<T-SR, becoming again negative below some lower temperature T*, where another phase transition takes place. (C) 2004 Elsevier B. V. All rights reserved.