Magnetic polarons in Eu-based films of magnetic semiconductors

Various films of magnetic semiconductors EuO, EuS, EuSe, and EuTe have been studied by low-energy muon spin relaxation (LE-mu SR) as well as by magnetization measurement techniques. LE-mu SR allows measurements of the distribution of magnetic field on the subnanometer scale unaccessible to traditional macroscopic techniques. A bound state of an electron around a positive muon-a magnetic polaron-is formed in the paramagnetic phase of Eu-based films up to room temperature. The local environment around the muon in the magnetic polaron is shown to be ferromagnetic.