Displacement of magnetic domain walls at high speeds - using gallium-substd. yttrium iron garnet in pulsed magnetic field

摘要

On a substrate of gadolinium gallium garnet, a film of gallium-substd. yttrium iron garnet is formed, by epitaxial growth from the liq.phase, with a pref. direction of magnetisation perpendicular ot the plane of the film. This element is placed in a gradient magnetic field (max. 6 kOe/cm.) thus creating a domain wall, and an auxiliary static magnetic field Hy of a few hundred Oe applied perpendicular to the domain-wall. using a coil connected to a generator, a pulsed, driving magnetic field Hz is created (build-up time 8 ns, repetition frequency 100 kHz) of max. strength 16 Oe. By means of Hy and Hz, the domain-wall can be displaced from one stable position to another, and with the aid of a polariser, analyser and photomultiplier, a ray of light passing through the film will be detected by the alteration in intensity due to the Faraday effect. The detection signal can be calibrated in terms of the wall displacement using ans oscilloscope and direct observation with a polarising microscope. The high speeds produced are suitable for use in data processing applications.