Magnetic domain imaging with a scanning kerr effect microscope

Abstract

A method for imaging magnetic domains with spatial resolution of less than 0.5 μm is described. The xhethod employs the mapeto optic Ken effcct and is applicable far obseming surface domain stmctwes, even if the magnetic surface of interest is covered by a thick transparent overcoat. Polarized laser light, incident at an oblique angle, is focused to a diffractian limited spot onto a surface whose magnetization is modulated at a heit frequency by a magnetic field. The modulation in the polarization of the light due tu the modulation of the magnetization beneath the spot is measured with the use of a lock in amplifier. AI image of the magnetization changes is then constructed by scanning the spot. Domains are reveded because areas of domain w d motion have larger magnetbation changes than areas of magnctizatian rotation within domains, Since this approach ininimizes noise and eliminates namagnetic signals, the domain image contrast is greatly enhanced. With 0.3 mW of laser power on a spot and a detection bandwidth of 10 Hz, signal to noise ratios of 6s db and a magnetization rotation sensitivity of 0.06' have been obtained in permtoy. Results of domain images in thin film inductive heads are presented. This technique is ideally suited far the study of the dynamics of wall motion and magnetization rotation in magnetic films. © 1986 IEEE