Effects of silver doping at the A-site on the structure, surface morphology, and magnetic behavior of La1−xAgxSrMn2O5+δ (x = 0.1 and 0.2)

Abstract

This study explores the impact of silver substitution at the A-site on the structural, morphological, and magnetic properties of La_1−xAg_xSrMn₂O_5+δ compounds, specifically for doping levels x = 0.1 and 0.2. The samples were synthesized using a conventional solid-state reaction method. X-ray diffraction (XRD) analysis confirmed that both compositions crystallize in a single-phase orthorhombic structure with the Pnma space group. Surface morphology and grain distribution were characterized via scanning electron microscopy (SEM), revealing microstructural changes associated with Ag doping. Temperature-dependent magnetization measurements indicate that Ag substitution leads to a reduction in overall magnetization, while the Curie temperature (T_p), associated with the ferromagnetic-to-paramagnetic transition, remains essentially unaffected. This transition was identified from the derivative of the magnetization versus temperature curves. At lower temperatures, subtle anomalies in the magnetization data suggest the possible emergence of short-range antiferromagnetic interactions or charge ordering tendencies, without evidence of a distinct AFM phase transition. Magnetocaloric properties were also evaluated, showing notable variations in magnetic entropy change (−ΔS_m) near the transition temperatures. The compounds exhibit relatively high values of relative cooling power (RCP), highlighting their potential for magnetic refrigeration applications.