The effect of Eu3+ ion doping in the La sites of single-crystal La4/3Sr5/3Mn2O7 was investigated. Electron spin resonance (ESR) was applied to La4/3Sr5/3Mn2O7 and (La0.8Eu0.2)4/3Sr5/3Mn2O7 single crystals. A phase separation and phase transitions were observed from the ESR spectra data. Between 350 K and 300 K, both paramagnetic resonance (PMR) and anisotropic ferromagnetic resonance (FMR) lines were observed in the ab plane and the c axis direction, suggesting a coexistence of the paramagnetic (PM) phase and the ferromagnetic (FM) phase. The magnetization measurement reveals a spin-glass-like behavior in single-crystal (La0.8Eu0.2)4/3Sr5/3Mn2O7 below the temperature of spin freezing Tf (∼ 29.5 K).

A Fe doped rutile TiO 2 single crystal is grown in an O 2 atmosphere by the floating zone technique. Electron spin resonance (ESR) spectra clearly demonstrate that Fe 3+ ions are substituted for the Ti 4+ ions in the rutile TiO 2 matrix. Magnetization measurements reveal that the Fe:TiO 2 crystal shows paramagnetic behaviour in a temperature range from 5 K to 350 K. The Fe 3+ ions possess weak magnetic anisotropy with an easy axis along the c axis. The annealed Fe:TiO 2 crystal shows spin-glass-like behaviours due to the aggregation of the ferromagnetic clusters.