Dysprosium containing bubble garnet composition for ion‐implanted contiguous disk devices

摘要

A new bubble garnet composition containing dysprosium (DySmLuBiCa)3(FeGe)5O12 has been investigated for use in 4‐μm period ion‐implanted contiguous disk (CD) devices. The most significant property of the material is its low value of difference in magnetostriction constants, δλ(=λ100-λ111=+1.4×10-6). The low δλ is attained by substituting Dy ions into the dodecahedral sites. The Gilbert damping parameter α is moderate. The present Dy‐containing garnet showed several favorable characteristics with respect to bubble propagation in 4‐μm period He+ implanted CD devices. Those characteristics are (1) small minimum drive field, (2) suppression of bubble jumping to adjacent CD ‘‘good’’ tracks, even in 6‐μm loop period, (3) smooth followup of bubble positions to drive field directions, and so on. These characteristics in bubble propagation along CD tracks are interpreted by the in‐plane magnetization reversal at the pattern edge, which is related to δλ and stress relief. Smaller δλ decreases threefold symmetric behavior of charged wall movement along pattern edges.