Analysis of the magnetoresistance contributions in a nanocrystallized Cr-doped FINEMET alloy

Abstract The magnetoresistance (MR) was measured at 200, 250 and 300 K in magnetic fields up to B =12 T for a nanocrystallized Fe 63.5 Cr 10 Nb 3 Cu 1 Si 13.5 B 9 alloy. Both the longitudinal (LMR) and transverse (TMR) component of the magnetoresistance decreased from B =0 to about 0.1 T. This could be ascribed to a giant MR (GMR) effect due to spin-dependent scattering of conduction electrons along their path between two Fe–Si nanograins via the non-magnetic matrix. Such a scattering may occur if the nanograin moments are not or only weakly coupled in the absence of a strong exchange coupling (due to the high Cr content in the matrix) and/or only weak dipole–dipole coupling is present (due to sufficiently large separations between the nanograins). For larger fields, the GMR saturated and a slightly nonlinear increase in MR with B was observed due to a contribution by the residual amorphous matrix. The anisotropic MR effect (AMR≡LMR−TMR) was negative for all fields and temperatures investigated. By measuring the MR of melt-quenched Fe 100− x Si x solid solutions with x =15, 18, 20, 25 and 28, the observed AMR could be identified as originating from the Fe–Si nanograins having a D0 3 structure.