Interelement spacing and angle effects on magnetic reversal in permalloy arrays

As high density integration of magnetic devices are realized, the role of interaction between small single domain islands becomes a very important concern. In a previous paper (IEEE Trans. Magn. vol.37, p.2049-2051, (2001)), we established that interconnected 30 nm thick Ni₈₁Fe₁₉ segments switch at a single field and the process appears to be governed by parallel rotation as described by modified Jacobs-Bean chain-of-spheres model. In this study, we focus on the switching characteristics of interelement submicron Ni₈₁Fe₁₉ segments as a function of spacing. A salient result is the increase of the switching field with decreasing spacing between the segments reaching the maximum value for zero spacing. Interestingly when the segments overlap, the switching field becomes lower than the maximum. In disjointed segments, effective external field is a combination of applied field and the monopolar stray-field from neighboring islands. In connected segments arrays, the spin-spin interaction dominates so that the switching field is determined by the reverse nucleation field at the ends of the array. We also investigated the reversal behavior of the connected segments as a function of the angle, α and the external field, H. The switching field dependence on α is also shown. The reversal field reaches minimum at 45°. A coherent rotation model which includes the effect of the array geometry will be used to explain these trends.