Engineering Sr‐Site Vacancies to Tailor Magnetocaloric and Magnetic Properties in Gd‐Doped La 0.67 Sr 0.33 MnO 3
Parvathy Namboothiri, B. Arun, M. VasundharaABSTRACT
We report the structural, chemical, magnetic, and magnetocaloric properties of Gd 3+ ‐substituted La 0.67 Sr 0.33 MnO 3 : stoichiometric La 0.6 Gd 0.07 Sr 0.33 MnO 3 (LSMO‐Gd) and its Sr‐deficient composition, La 0.6 Gd 0.07 Sr 0.33‐ x MnO 3 ( x = 0.07) (LS d MO‐Gd). Both compounds were synthesized by the solid‐state method and their phase formation was confirmed by X‐ray diffraction along with Rietveld refinement confirmed the formation of a rhombohedral R ‐3 c perovskite structure, with a minor Mn 3 O 4 secondary phase detected only in the Sr‐deficient sample. Scanning electron microscopy revealed dense microstructures with an average grain size of ∼5 µm, while energy‐dispersive X‐ray spectroscopy and elemental mapping confirmed homogeneous elemental distribution. X‐ray photoelectron spectroscopy showed mixed Mn 3+ /Mn 4+ valence states in LSMO‐Gd, whereas LS d MO‐Gd exhibited the coexistence of Mn 2+ , Mn 3+ , and Mn 4+ due to Sr‐site deficiency. X‐ray fluorescence spectroscopy further verified the intended compositional variation through reduced SrO and increased La 2 O 3 /Gd 2 O 3 fractions in LS d MO‐Gd. Magnetic measurements revealed that Sr‐site deficiency shifts the T C closer to room temperature. Although the Sr‐deficient sample exhibits a slightly lower Δ S M under an applied field of 5 T, it demonstrates an enhanced refrigerant capacity, highlighting the efficiency of Sr‐site defect engineering for near‐room‐temperature magnetic refrigeration.