The magnetic anisotropy of 111 oriented garnet bubble films

Abstract

In order to tailor magnetic materials for bubble applications it is important to have a model that can be used to predict the effective anisotropy of a given composition or to select a composition that will have the correct anisotropy to achieve desired bubble size and Q. A model is described in this paper which seems to agree with observed anisotropies over the complete range of bubble sizes for 111 oriented films of mixed rare earth garnets. The elements of the model are as follows: (a) The total effective anisotropy, K T=KS+KG; (b) KS=-10 12λ111Δa/2.9; (c) KG=J ijKijxixj@qL, where the sum is over all pairs of ions involving Sm or Eu, in amount xi, and smaller ions such as Y, Tm, Yb, Lu, in amount xj, where x is the atomic abundance (0-3) in the formula unit. (d) Both λ111 and KG are reduced by A/A0 corresponding to the dilution by Ga or CaGe. The paper gives values for Kij, λ111 and A/A0 to be used. A rationale for the model is also given although the principal justification for the model is its apparent success in projecting values of magnetic anisotropy in 111 oriented films.