Magnetization reversal in sub-100 nm pseudo-spin-valve element arrays

The magnetization reversal exhibited by arrays of 70-nm-wide pseudo-spin-valve (PSV) elements has been investigated by measurements of minor hysteresis loops. Samples were patterned from sputtered NiFe (6 nm)/Cu (3 and 6 nm)/Co (4 nm)/Cu (4 nm) magnetic thin film stacks. The overall room temperature magnetic behavior of the arrays can be understood by considering a distribution of switching fields for both the hard (Co) and soft (NiFe) magnetic layers. Such layers interact through exchange and magnetostatic coupling. Increasing the lengths of the elements leads to narrower switching field distributions and higher mean switching fields (particularly for the hard layer). On the other hand, decreasing the thickness of the Cu spacer leads to an increase of the switching field of the hard layer. Results obtained are well described by a model that treats each PSV as a coupled pair of rectangular single-domain films and uses the values of the interaction field between layers deduced from experimental minor loops.