Structure and Magnetic Properties of Eu_1–xSr_xMnO₃ (x = 0.0, 0.25) Manganites

Eu_1–xSr_xMnO₃ (x = 0.0, 0.25) manganites have been characterized by X-ray diffraction, thermal analysis, and magnetometry. At room temperature, they have a perovskite-like structure, with space group Pbnm. Partial heterovalent substitution of Sr²⁺ for Eu³⁺ cations reduces the Jahn–Teller (JT) distortion of the crystal structure of the manganites because of the decrease in the number of Mn³⁺ ions involved in the distortion mechanism. As the temperature is raised, the europium manganites undergo a transition from an ordered to a disordered state (JT transition), and substitution of strontium for 25% of europium cations lowers the structural JT transition temperature by more than a factor of 4. The manganites undergo a paramagnetic–antiferromagnetic phase transition with a characteristic Néel temperature (T_N). Substitution of Sr for 25% of Eu cations raises T_N from 49 K at x = 0.0 to 65 K.