Critical behavior of the magnetoresistance of Gd near the Curie point: an experimental test of theoretical models

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Abstract
High-resolution magnetoresistance measurements, Delta rho (T,H), have been performed on a single crystal of Gd, with the electric current and magnetic field (H) directed along the c axis. The data cover the immediate vicinity of the Curie temperature Tc(1.4*10-3c; 8*10-4-2, T> epsilon , where h is reduced field) for h/ epsilon or approximately=6*10-2, but with h/ epsilon still much smaller than 1, a new regime appears, characterised by a strong departure from the previous dependence. Below Tc the low-field theoretical prediction Delta rho varies as h was found to be valid over a wide range of the ratio h/ mod epsilon mod , at least up to h/ mod epsilon mod approximately 0.9; the temperature dependence of Delta rho was in disagreement with the theoretical expectations ( Delta rho varies as mod epsilon mod 1- alpha - beta delta ), the results showing a much weaker temperature dependence just below TC. A brief discussion is also presented for experimental situations where the low-field condition h>> mod epsilon mod begins to fail.