A system for measurement of domain wall motion in amorphous rare earth-transition metal alloys

A system has been developed for measuring domain wall motion in amorphous rare earth-transition metal alloys. A one-dimensional scanning technique is utilized oscillating a focused HeNe laser spot over the magnetization pattern in the film. Domain walls are detected through the polar Kerr effect as the spot scans the film. A magnetic field is applied to the film in order to move the domain walls. The maximum line scanning rate is about 250 Hz. The spot diameter at a 632.8 nm wavelength is limited to about 8 µm by the 0.46 numerical aperture of the focusing objective. the beam waist of the laser. and aberrations. The domain wall position can be measured to within ±1 µm. The apparatus is described and domain wall motion measurements are presented.