Interaction of domain walls with localized stress fields in magnetostrictive films

Abstract

The interaction of magnetic bubble domains with overlying patterned metallizations is described in terms of a model in which local stress fields from the metal edges perturb the energy of domain walls through inverse magnetostriction. Examined in detail is the case in which a straight wall passes under the edge of a metal film deposited in either tension or compression. Using a simple form for the stress field generated at such a boundary, we show that the domain-wall energy is substantially perturbed in the immediate vicinity of the edge. This gives rise to either an attractive or repulsive interaction, depending on the signs of the stress and of the magnetostriction coefficients. The predictions of the model are examined by observing experimentally the interaction of straight domain walls and bubbles with metal stripes under compression. Comparison of the predicted and observed forces required to pull the domain walls away from the metal edges verifies the model calculations over almost two decades of metal stress. The use of a space layer to reduce the stress in the magnetic material is found to significantly lower the bubble-metallization interaction, thereby permitting improved device performance.