We have investigated the magnetic and magneto-optical propertices of the compositionally modulated Co/NM (NM = Pd, Pt) multilayers. The origins of perpendicular magnetic anisotropy and magneto-optical effects were investigated. The samples were prepared at the Ar sputtering pressure of 10 mTorr by a dc magnetron sputtering technique. To measure the magneto-optical effects of the samples, we have constructed a magneto-optical (MO) hysteresis loop tracer which could measure not only the Kerr rotational angle but also the Kerr ellipticity, using a HeNe laser (632.8 nm) as a light source and an electromagnet with a maximum applied field of ± 15 kOe. The Kerr rotational angle was measured by adopting a differential detection method using a polarizing beam splitter and a home-made differential amplifier. The Kerr ellipticity was measured by inserting a quarter-wave plate in the path of the reflected beam. The MO-loop tracer could measure the Kerr rotational angle and ellipticity up to ± 1.4° with a noise level of less than 0.005°.
The effects of Pd predeposition layer on magnetic properties in compositionally modulated Co/Pd multilayers were also investigated. The thickness of Pd predeposition layer was varied from 0 to 1000Å with 100-Å interval. It was observed that the magnetic properties of the saturation magnetization, the perpendicular anisotropy energy, and the coercivity were remained relatively constant until the thickness of predeposition layer was up to 600Å. However, those were rapidly increased with the predeposition-layer thickness when the thickness was thicker than 700Å. The results were caused by change of the microstructure of the multilayers deposited on different predeposition-layer thicknesses.
