Hall effect in amorphous thinhyphen;film magnetic alloys

摘要

Amorphous magnetic alloys have unusually large extraordinary Hall coefficients (Rs) defined by the ratio of the Hall resistivity to the net magnetic moment of the alloy. We have studied the Hall effect in amorphous films in the ternary ferrimagnetic systems Cohyphen;Gdhyphen;Mo and Cohyphen;Gdhyphen;Au, alloys which exhibit compensation temperatures (Tcomp). AboveTcompthe Hall coefficientRsis positive and belowTcompthe sign ofRschanges to negative in a discontinuous manner, probably limited by the homogeneity of the sample. We have also prepared amorphous Gdhyphen;Au and Yhyphen;Co films and measuredRswhich we use to qualitatively separate the effects of the Co and Gd sublattices in the ternary alloys. We attribute the sign ofRsto a combined effect of a negative Gd and a positive Co Hall coefficient. AboveTcompthe Co is dominant and points in the direction of the applied fieldHwhile Gd is antiparallel toH. Thus, both sublattices contribute in a positive sense toRs. BelowTcompthe Gd moment is dominant and the sign ofRsis reversed for both sublattices. Values ofRsup to 25times;10minus;9OHgr;thinsp;cm/G are measured nearTcompand when Mo is presentRsis reduced to 5times;10minus;9OHgr;thinsp;cm/G. Molybdenum is known to cause a strong decrease in the moment of the cobalt sublattice and this probably is the reasonRsdecreases. Our interpretation of the Hall effect in these ferrimagnetic systems differs from other recently proposed models.