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Perpendicular magnetic tunnel junctions (p-MTJs) were patterned into nanopillars using electron-beam lithography to study their scaling and switching behaviour. Magnetoresistance measurements of annealed and unannealed p-MTJ films using scanning probe microscopy showed good agreement with Monte Carlo modeling. p-MTJ pillars demonstrated clear parallel magnetic states, both 'up' or both 'down' following AC-demagnetization. Significant variability in the resistance of p-MTJ pillars was observed and attributed to edge features generated during patterning or local inhomogeneity in the MgO layer.

A study of macroscopic quantum tunneling (MQT) of the magnetic moment in systems with quadratic and higher order uniaxial anisotropy and Zeeman interaction is presented. By using the instanton technique, under the giant spin approximation, the escape rate or probability per unit of time Gamma that the system undergoes a transition between coherent or metastable states is calculated. Using an effective particle potential we also determine the escape temperature T(e)(T), which marks the transition from quantum tunneling to thermal activation. A discussion is presented about the different models and the behavior of the magnetic system under the tunneling regime.

The investigation of the role of interactions in magnetic wire arrays is complex and often involves substantial simplifications. In this paper analytical expressions taking into consideration the geometry of the wires and dipolar interactions between them have been obtained. An expansion of these terms, at first order, can be easily evaluated and shows a good agreement with the total expression for the energy. The extent of the interwire magnetostatic coupling has also been investigated, and it is shown that the number of wires required to reach a size independent magnetic state in the array strongly depends on the relative magnetic orientation of the wires.