Angle and thickness dependence of magnetoresistance peaks in thin nickel films

In this paper, we report a dependence of the magnetoresistance in thin nick el films on the angle theta between the magnetic field and the film surface . We find a strong variation of the magnetic field difference between two M R peaks (FDMP). In thinner films less than 400 Angstrom thick, the FDMP is well explained by a 1/cos theta function, which can be obtained using the c oncept of an effective magnetization field. However, in thicker films, the FDMP's rate of increase is found to become faster than 1/cos theta. This di fferent behavior is considered to be related to both the grain formation an d the grain size in the films. Consequently, due to the different grain con figuration, randomization of the magnetization vectors during the reversed magnetic field process in thicker films might be achieved through a three-d imensional process while in thinner films this is achieved through a two-di mensional process. (C) 2000 Published by Elsevier Science Ltd.