The effect of Eu3＋ ion doping in the La sites of single-crystal La4/3Srs/3Mn2O7 was investigated. Electron spin resonance （ESR） was applied to La4/3Sr5/3Mn2O7 and （Lao.8Euo.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 （Lao.8Euo.2）4/3 Sr5/3Mn2O7 below the temperature of spin freezing Tf （- 29.5 K）.
A polycrystalline sample Ndo.5Sro.3Cao.2MnO3 is prepared by the conventional solid state reaction method. The structure and magnetic properties are investigated with x-ray diffraction （XRD） patterns, a superconducting quantum in- terference device （SQUID）, and electron spin resonance （ESR）. The sample is in single phase with the space group Pbnm symmetry. With the decrease of temperature, Ndo.sSro.3Cao.2MnO3 undergoes three magnetic transitions： ferromagnetic transition at Tc ≈ 210 K, charge-ordering at Tco ≈ 175 K, and antiferromagnetic transition at TN = 155 K. In addition, the activation energy Ea ≈ 52.78 meV can be extracted by curve fitting.
