Magnetoresistive tunnel junctions deposited on laterally modulated substrates

Co/Al₂O₃/NiFe tunnel junctions were deposited on misoriented silicon substrates. A thermal treatment activates a step bunching mechanism on the silicon surface leading to a modulated topology with a nanometric lateral period. The bottom magnetic electrode and the barrier follow this topology. Such junctions present good magnetotransport characteristics with a magnetoresistance about 14% at room temperature. Due to the uniaxial anisotropy induced by the topological modulation, the antiparallel configuration of the magnetization is well defined leading to perfect square magnetoresistance cycles at all temperatures. The magnetic behavior of patterned junctions has been investigated by transport measurements and Kerr microscopy. More than inducing a strong uniaxial anisotropy, the modulated topology is shown to strongly influence the switching mechanism of the magnetization.