Ion Implanted Patterns for Magnetic Bubble Propagation

Abstract

Localized ion implantation through photoresist masks has been used to produce rails which guide bubbles in garnet epitaxial films. Implantation expands the lattice so that the implanted regions are in lateral compression. In garnets with negative magnetostriction, these shallow regions have stress‐induced easy axes parallel to the film surface. Bubbles adhere to the edges of the implanted regions due to magnetostatic and magnetostrictive effects. Using overlaying conductor patterns, bubbles in these tracks have been propagated at frequencies up to 600 kHz. No harmful effects on mobility or coercivity have been observed and “hard bubbles” are suppressed under the implanted regions. Ion implantation also provides a new method of producing field‐access bubble propagation patterns directly in garnet films. The in‐plane magnetization in the implanted regions can be rotated by an in‐plane applied field. Bubbles in the underlying garnet follow the moving poles at the edges of the implanted regions. The implanted layer thus takes the place of a superimposed Permalloy pattern. Propagation at 100 kHz rate has been achieved in a 35 Oe rotating field using a simple repeated half circle pattern implanted with protons (2×1016/cm2 at 100 keV in YGdTmFe4.3Ga0.7O12). This propagation method requires no metallization, leaves the surface of the film planar and allows clear optical viewing of the propagating bubbles.