LARGE POSITIVE MAGNETORESISTANCE AT LOW-TEMPERATURES IN A FERROMAGNETIC NATURAL MULTILAYER, LAMN2GE2

The results of magnetoresistance measurements on a naturally occurring multilayer LaMn2Ge2, which is ferromagnetic below 326 K, are reported . The magnitude of magnetoresistance is found to be positive below 70 K gradually increasing to an unusually large value (nearly 100%) at 4. 2 K in the presence of a field of 70 kOe as the temperature is lowered , similar to the recent observations by Verbanck, Temst, Mae, Schad, V an Bael, Moshchalkov, and Bruynseraede [Appl. Phys. Lett. 70, 1477 (19 97)] in Cr/Ag/Cr trilayers. The positive sign of magnetoresistance for a ferromagnet is unexpected and possible explanations are offered. (C ) 1997 American Institute of Physics.