Abstract: Magnetoresistance through the spin-glass regime of amorphous Fe-Ni-P-B

Abstract

We report first detailed magnetoresistance (MR) studies of amorphous magnetically dilute FexNi1−xP14B6 alloys with x=3,5,7,11 and 13, in applied fields, B, to 22 T and for temperatures above 0.1 K. The resistance minimum, observed in all these alloys, occurs at a maximum temperature of 100 K for x=5 alloy, a consentration at which a transition from spin glass to mictomagnetic behavior has been reported.1 The (MR) in all these alloys, which can be as large as −1%, has a strong T-dependence over a wide temperature range both below and above the spin freezing temperature Tf (or Tc for x≳11). Above Tf(Tc) the B dependence of (MR) is −ve but with a curvature indicative of cluster effects. Also even at 0.2 K no saturation effects are observed in the −ve (MR) up to 22 T. The overall rise in resistance R(T)/Rmin decreases with increasing Fe conc. for x≳5. It is striking that for all these alloys the resistance is found to increase with decreasing T even at 0.1 K with no indications of any spin freezing effects. Thus the low T resistivity behavior of these amorphous alloys is markedly different from those usually observed in crystalline spin glasses. Supported by NSF grants DMR 77−08599 and DMR 76−80994 resp. 1David Onn et al., J. Appl. Phys. 49(3), 1730 (1978).