Static properties of magnetic bubbles in garnet films with orthorhombic anisotropy

Abstract

The static properties of bubbles in (110) oriented garnet films of composition (Gd, Y)3 (Fe, Mn, Ga)5O12 have been studied. The anisotropy in these films is orthorhombic with the easy axis of magnetization perpendicular to the plane of the film and a secondary easy axis in the plane of the film. Two types of bubbles can be distinguished, A-type bubbles having no Bloch lines and B-type bubbles with Bloch lines. Magnetic fields parallel to the in-plane easy axis of magnetization have a strong influence on the diameter and on the collapse field. Whereas the properties of the B-type bubbles are independent of the sign of this in-plane field, the properties of the A-type bubbles do depend on the sign of this in-plane field. B-type bubbles easily change state and become A-type under influence of in-plane fields. At zero in-plane field the collapse fields of B-type bubbles are about 1 to 3% larger than the collapse fields of A-type bubbles. A theory is presented that takes into account the interaction between in-plane field and domain wall magnetization. In this way the experimental data obtained for the A-type bubbles are reproduced very well. The difference between the collapse fields of A- and B-type bubbles in zero in-plane field is explained by taking into account the influence of stray fields and Bloch lines on the domain wall energy.