Effect of Low-level Doping With Strontium On Structure, Magnetism, and Electron States in SmMnO₃ Manganite

Manganites of rare earth elements are currently promising materials for electronics, catalysis, current sources and other applications. Their widespread demand is caused by a variety of structural and magnetic effects connected with substitutions in the sublattices of rare earth element and manganese. Substitutions of rare earth element by Sr, Ca, or Ba in manganites are known to impact the Jahn-Teller (JT) transition temperature as well as the concentration of Mn³⁺ and Mn⁴⁺ ions, which influences the efficiency of double exchange in magnetic orderings. In this work, solid solution Sm_1-xSr_xMnO₃ with low concentrations of the substituting element x = 0; 0.15; 0.25 has been studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermal analysis, and magnetometry. Samarium manganites have a perovskite-like orthorhombic structure (Pbnm space group). It has been shown that the Sm-by-Sr substitution leads to a gradual increase in the valence of manganese from 3 + to intermediate value 3.67+. This is accompanied by an increase Néel temperature in (T_N) from 56 K at x = 0 to 90 K at x = 0.25, in the paramagnetic Curie temperature (Θ) from − 30.3 K at x = 0 to 119.9 K at x = 0.25, as well as in the value of the saturation magnetic moment (µ_S) from 0.27 µB at x = 0 to 3.49 µB at x = 0.25. In addition, such substitution leads to a decrease in the temperature of the JT structural transition from 996 ºC at x = 0.0 to 252 ºC at x = 0.25. The relationship between the magnetic properties and the crystal structure of samarium manganites is discussed.