Micromagnetism and high temperature coercivity of MnBiÕAl multilayers

The micromagnetic properties of multilayered MnBi/Al films have been investigated and compared to pure MnBi thin films. Pure MnBi films reveal an anomalous increase of the high temperature coercivity, which has been explained on the basis of a hybrid domain wall pinning model. The multilayer-type preparation of MnBi/Al thin films results in significantly reduced MnBi particle size of approximately 40 nm. The smaller particle size leads to a change of the dominant magnetization reversal process from one driven by domain wall movement toward coherent rotation. This was investigated via magnetic force microscopy imaging and micromagnetic calculations. The absence of domain walls during magnetization reversal results in a clear suppression of the increase of the high temperature coercivity observed in pure MnBi films. © 2000 American Institute of Physics. @S0021-8979~00!01620-0#