Magnetization Reversal in Focussed Ion-Beam Implanted YIG Patterns

Abstract

Magnetization reversal in Bi- and Ga-substituted YIG film rectangular patterns, formed by micro-lapping and subsequent acid etching, is based on the nucleation and extension of reverse domains. As the pattern size is reduced from 300×300 μm to less than 100×100 μm, the nucleation field (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> ) increases from 100 to 530 Oe, equal to the anisotropy field. To control the H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</inf> , an artificial magnetic defect was formed in the center of the pattern by using focussed ion-beam implantation. When Ge- or Si-ions were implanted at 50 keV in a spot 0.3 μm in diameter, the H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> dropped to less than 330 Oe. As the Ge ion-implanted area was extended, the H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> gradually decreased. Assuming that the ion-implanted region is a reverse-domain nucleus, the H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> was calculated as the external field for which the maximum total magnetic energy is attained. Theoretical values of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> agreed well with experimental ones.