Remanence and coercivity in exchange coupled amorphous R-TM/Fe bilayers and multilayers (abstract)

Abstract

We have investigated the hysteresis behavior of rare-earth (R)-transition metal (TM) bilayers and multilayers consisting of a fine mixture of hard and soft phases. The films with bilayer thickness in the range of 5–100 Å were fabricated using a dc sputtering system. X-ray diffraction was used to check the crystal structure and multilayer structure. The magnetic properties were measured with a SQUID magnetometer in the temperature range of 10–300 K with fields up to 55 kOe. A strong exchange coupling between the hard magnetic phase (R-TM) and the soft phase (Fe) leads to a smooth hysteresis loop in samples with a certain thickness range. The remanent magnetization is enhanced significantly at the expense of a reduced coercivity. For example, in NdFe/Fe multilayer films, the reduced remanence increases from 0.63 to 0.92 at 10 K while the coercivity decreases from 9.3 to 1 kOe as the Fe layer thickness is varied from 0 to 10 nm. The effect of interface roughness on the exchange coupling has been investigated via different sputtering pressures and rates. The dependence of magnetic hysteresis on the layer thickness and temperature has been examined and the results will be reported.