An electron spin resonance study of Eu doping effect in La_4/3Sr_5/3Mn₂O₇ single crystal

The effect of Eu³⁺ ion doping in the La sites of single-crystal La_4/3Sr_5/3Mn₂O₇ was investigated. Electron spin resonance (ESR) was applied to La_4/3Sr_5/3Mn₂O₇ and (La_0.8Eu_0.2)_4/3Sr_5/3Mn₂O₇ 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 (La_0.8Eu_0.2)_4/3Sr_5/3Mn₂O₇ below the temperature of spin freezing T_f (～ 29.5 K).