${\mathrm{Ge}}_{1-x}{\mathrm{Mn}}_x\mathrm{Te}$ is shown to be a multiferroic semiconductor, exhibiting both ferromagnetic and ferroelectric properties. By ferromagnetic resonance we demonstrate that both types of order are coupled to each other. As a result, magnetic-field-induced ferroelectric polarization reversal is achieved. Switching of the spontaneous electric dipole moment is monitored by changes in the magnetocrystalline anisotropy. This also reveals that the ferroelectric polarization reversal is accompanied by a reorientation of the hard and easy magnetization axes. By tuning the GeMnTe composition, the interplay between ferromagnetism and ferroelectricity can be controlled.

Low temperature, infrared, and visible-ultraviolet absorption spectra of yttrium aluminum garnet (YAG) bulk crystals and epitaxial layers doped with Ce are presented. In the region of intra-configurational 4f–4f transitions, the spectra of the bulk YAG crystals exhibit existence of at least two different Ce3+ related centers, a major one associated with Ce in regular positions substituting yttrium and also additional center, due to so called antisite positions in the garnet host, i.e., ions in the Al positions. Crystal field analysis based on exchange charge model exhibit excellent agreement with the experimental data for major Ce3+ center.