Temperature dependence of field-cooled (filled symbols) and zero-field-cooled (open symbols) magnetization for all compounds, measured at 200 Oe.
Magnetic isotherms at various temperatures around TC for (a) , (b) , (c) , and (d) samples. The main difference is that exhibits a metamagnetic transition, suggesting that the compound presents first-order magnetic transition. The Arrott plots for all studied compounds are shown in the Figures 2(e)–2(h) .
Magnetic-entropy change as a function of temperature for and for , 20, 30, 40, and 50 kOe. Inset: Dependence of the maximum-magnetic entropy change ( ) on the applied magnetic-field change for and . The displacement of peak with increasing changes from 292 K up to 296 K for and from 120 K up to 126 K for .
Dependence of magnetic entropy change and the Curie temperature on the average ionic radius of the A-site and tolerance factor. With decreasing , the structure becomes more distorted, which gives rise to a structural transition from rhombohedral (high symmetry) to orthorhombic (low symmetry).
Crystal lattice parameters and mean crystallite size values for all samples based on Rietveld refinement.
Maximum magnetic entropy change ( ) for peak half width ( ) and RCP.
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