Kerr Effect Investigations of Magnetic Interlayer Interactions in EuS-PbS Multilayers

Kerr magnetometry was employed to study the temperature dependence of magnetization and magnetic hysteresis loops in ferromagnetic EuS-PbS semiconductor multilayers in the temperature range T=3-35 K at low magnetic fields H≤150 Oe. For EuS-PbS/KCl(100) structures with ultrathin non-magnetic PbS spacer of 1~nm, we observed a maximum on the temperature dependence of magnetization at low fields H≤30 Oe. For higher fields, we found for these structures a regular mean-field-like increase in magnetization with decreasing temperature. The same regular behavior was also found for EuS-PbS/KCl structures with thicker PbS spacer, as well as for all EuS-PbS/BaF$\text{}_{2}$(111) multilayers independently of spacer thickness. For qualitative interpretation of these findings, we consider two magnetic contributions to the total energy of EuS-PbS multilayers: the Zeeman energy and the antiferromagnetic interlayer exchange coupling between ferromagnetic EuS layers via diamagnetic PbS spacer.