Magneto-optic measurements in the 1.5–6.7 eV range for thick fcc and hcp Co films (abstract)

Abstract

As the development of solid-state diode lasers for shorter wavelengths is progressing steadily, the approach for high-density magneto-optical recording at shorter wavelengths becomes more feasible. Therefore, the study of magneto-optical effects in a wavelength range shorter than blue is essential for the exploration of new materials for such high-density recording media. In this study, a novel magneto-optical measurement system covering a wide wavelength range from 185 to 900 nm (1.5–6.7 eV) at temperatures from 80 to 600 K has been built. In order to cover such a wide wavelength range, two lamp sources are used: a high-power deuterium lamp for photon energies above 4 eV and a Xe lamp for less than 4 eV. A “continuous” calibration principle has been utilized to assure a high accuracy for measurement of rotation and ellipticity. The entire measurement is automated and computer controlled by software written in Labview. In Co/Pt-based multilayers, the origin of the high negative Kerr rotation at around 4 eV is generally attributed to the polarized Pt. On the other hand, the texture of these layers is generally strongly fcc. Therefore, the Kerr rotation of fcc Co, rather than hcp Co, should be known to understand these layers, and to be able to estimate the respective contributions from the Pt and the Co layers. In this work, results for thick hcp and fcc Co layers are shown. A 1000 Å Co (111) film showed a maximum Kerr rotation of about −0.5° at 4 eV, which is higher by about −0.1° than the rotation obtained for hcp Co. Further, a positive Kerr rotation of about +0.3° was found at about 6 eV. For 1000 Å fcc Co (100) films Kerr rotations between +0.3 and +0.4° were found at 5.5–6 eV. These values coincide with almost zero Kerr ellipticity. Above this photon energy the Kerr rotation decreases again.