The role of trapping levels of nonequilibrium electrons during the formation of pinning centers for domain walls in the magnetic semiconductor CdCr2Se4

A complex study of electrical conductivity and photoconductivity in constant and variable electric fields, thermally stimulated conductivity, and the photoferromagnetic effect are carried out in the temperature range 10–300 K for a CdCr2Se4 magnetic semiconductor with various concentrations of Ga impurity and Se vacancies (VSe). The phenomenon of hopping photoinduced conduction is observed for the first time. It is shown that shallow donor levels that exchange photoelectrons trapped by them with Cr3+ magnetic ions may be responsible for the photoferromagnetic effect. As a result of this exchange, the Cr3+ ions acquire valence and spin instabilities, which lead to nonequilibrium pinning of the domain wall by these ions.