Magnetoresistance of Pd3Fe and PdFe

Abstract

The ferromagnetic anisotropy of resistivity Δρ/ρ0= (ρ∥-ρ⊥)/ρ0 of the alloy Pd70Fe30 has been measured below 295 K, for each of five different thermal treatments. At 4.2 K, Δρ/ρ0 reaches 9.4% in the atomically ordered state (of Pd3Fe type), but is only 5.4% in the disordered state. In Pd75Fe25, the effect of ordering on Δρ/ρ0 is much smaller than in Pd70Fe30, and has the opposite sign. A similar sign reversal with varying iron concentration has been observed earlier in the Ni-Fe series. Most features of our Δρ/ρ0 data, including the sign reversal, can be explained on the basis of the well-known linear relation between Δρ/ρ0 and the ratio ρ↓/ρ↑ of the resistivities for spin-down and spin-up 4s electrons. In Pd50Fe50, ordering (of PdFe type) has little effect on Δρ/ρ0. At 295 K, where phonon scattering dominates over impurity scattering, Δρ/ρ0 is always smaller than 1% in all samples.