Magnetization reversal of NiFe films exchange-biased by IrMn and FeMn

We have used the transmission electron microscope to study how the magnetization reversal mechanism of thin NiFe layers exchange-biased by IrMn and FeMn varies over a wide temperature range, The reversal behaviour was qualitatively similar for layers biased by both types of antiferromagnet, At room temperature and below the most striking feature was the scale of the domain structures observed. Very high density domain structures with micron (or sub-micron) wall separations developed. By contrast at elevated temperatures, the reversal mechanism simplified. This is consistent with there being a strong local variation of the pinning strength between the NiFe and the antiferromagnetic layer, The overall temperature variation of the pinning changes much more rapidly than the magnetic properties of an isolated NiFe layer over a similar temperature range.