Competition Between Interlayer Exchange and Zeeman Energies on the Way to Saturation of Magnetization in Fe/Cr Multilayers

We have studied the field and temperature dependence of magnetization on ion-beam sputtered Fe/Cr multilayers. The samples were characterized by small angle x-ray reflectivity and grazing incidence x-ray diffraction techniques. The temperature dependence of the magnetization at the saturation field (Hsat) is interpreted in terms of the spin-wave theory with an additional paramagnetic contribution from the nanometer size Cr. At moderately high magnetic fields but below Hsat, an unusual increase in the magnetization with temperature, for samples of higher Cr thickness, was observed. The presence of an anomalous peak, especially for the highest Cr thickness sample at around room temperature and at magnetic fields as high as 2 T, is believed to appear as a result of an intricate competition between the Fe–Fe interlayer exchange coupling and the Zeeman energy of the outer Fe spins for the requirement of the minimum energy state.