Magnetic circular dichroism in amorphous GdCoMo films

Extending earlier studies of the polar Kerr effect θ of bias sputtered amorphous GdCoMoArO films, we have studied the ellipticity ε of the reflected light, which arises from magnetic circular dichroism. In certain cases ε is comparable in size to θ. A surface layer formed by oxidation gives a contribution which adds to the bulk θ but substracts from the bulk ε. The surface layer can be removed and the samples passivated simply by sputter etching. The substrate interface has appreciably different θ and ε from the bulk. The bulk θ and ε both drop with increase in Mo. θ appears insensitive to Gd and O while ε increases with Gd or O.