Experimental study on interlayer magnetic coupling in sputtered Al/Fe/Al/Gd magnetic multilayer films. 2. Hysteresis curves of x-ray magnetic circular dicroism at the Gd-L3 edge

The spacer thickness dependence of the interlayer magnetic coupling (IMC) between Gd and Fe layers separated by Al spacers has been studied. Magnetization measurement and X-ray magnetic circular dicroism (XMCD) spectroscopy at the Gd-L3 edge have been carried out on sputtered Fe (20 A)/Al (R A)/Gd (40 A) multilayer films (MLFs) for R=0, 5, 10, and 100 and on some reference films. Experimental data at low magnetic fields below 1 kOe are carefully investigated. A simple theoretical model is introduced to evaluate the strength of IMC. The energy of IMC is represented by the term JMFe·MGd, in which MFe and MGd denote the average overall magnetic moments of Fe and Gd layers, respectively. It is found that J, which is evaluated from the magnetization curves and the Gd-XMCD signals, is 370 x 104 Oe·cm2/emu for MLF of R=0, and can be reduced by one order of magnitude when R is changed from 0 to 10. Most of characteristic features of the experimental data are ascribed to the varing magnetization of Gd layers. It is found that 40 A Gd layers, which are paramagnetic at 5 K when isolated using 100 A Al spacers, show magnetic hysteresis when sandwiched between Fe layers. (author)