Observation of magnetic domain structure and switching in barium ferrite thin films

摘要

Magnetic domain structure and switching mechanism were investigated in individual barium ferrite grains with sizes ranging from 0.5-7 /spl mu/m. Magnetic force microscopy (MFM) was used to image grains in sputtered Pt-doped barium ferrite thin films. The switching thresholds of the different grains were measured by applying successively larger magnetic fields to the sample and observing which grains switched. Application of a field to as-annealed samples swept out multidomain structures at a field of H/sub ini//spl ap/1000 Oe, which was relatively independent of grain size. It was found that, after the grains had been saturated, a different field H/sub rev/ had to be applied to saturate the grain in the opposite direction in large size grains (about 4 /spl mu/m) H/sub ini//spl ap/H/sub rev/; whereas for grains with sizes of 1-3 /spl mu/m, H/sub rev/ varies from approximately equal to H/sub ini/ to many times larger. Domain wall motion was found to dominate the reversal process in grains larger than 4 /spl mu/m, as suggested by discontinuous magnetization jumps and an inverse-cosine angular dependence of H/sub rev/. Reversal in grains with sizes between 0.5 and 1 /spl mu/m is believed to be dominated by incoherent rotation, as indicated by the angular dependence of H/sub rev/.