Residual resistivity ratio and its relation to the magnetoresistance behavior in LaMn 2Ge 2-derived alloys

Abstract

Results of low temperature magnetoresistance ( Δρ/ ρ) and isothermal magnetization (M) measurements on polycrystalline ferromagnetic(T C close to 300 K) natural multilayers, LaMn 2± x Ge 2− y Si y , are reported. It is found that the samples with large residual resistivity ratio, ρ(300K)/ ρ(4.2K), exhibit large positive magnetoresistance at high magnetic fields. The Kohler's rule is not obeyed in these alloys. In addition, at 4.5 K, there is a tendency towards linear variation of Δρ/ ρ with magnetic field with increasing ρ(300K)/ ρ(4.2K); however, the field dependence of Δρ/ ρ does not track that of M, thereby suggesting that the magnetoresistance originates from non-magnetic layers. It is interesting that these experimental findings on bulk polycrystals are qualitatively similar to what is seen in artificially grown multilayer systems recently.