RESIDUAL RESISTIVITY RATIO AND ITS RELATION TO THE MAGNETORESISTANCE BEHAVIOR IN LAMN2GE2-DERIVED ALLOYS

Results of low temperature magnetoresistance (Delta rho/rho) and isoth ermal magnetization (M) measurements on polycrystalline ferromagnetic (T-C close to 300 K) natural multilayers, LaMn2+/-x,Ge2-ySiy are repor ted. It is found that the samples with large residual resistivity rati o, rho(300K)/rho(4.2K), exhibit large positive magnetoresistance at hi gh magnetic fields. The Kohler's rule is not obeyed in these alloys. I n addition, at 4.5 K, there is a tendency towards linear variation of Delta rho/rho with magnetic field with increasing rho(300K)/rho(4.2K); however, the field dependence of Delta rho/rho 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 artifi cially grown multilayer systems recently. (C) 1998 Elsevier Science Lt d. All rights reserved.