Influence of crystallite size reduction on the magnetic and magnetocaloric properties of La0.6Sr0.35Ca0.05CoO3 nanoparticles

Abstract In this paper, three samples of La 0.6 Sr 0.35 Ca 0.05 CoO 3 with different crystallite sizes were prepared by a combination of the sol–gel and mechanical milling methods, with milling times t m of 0 (M0), 1 h (M1) and 2 h (M2). From the XRD and SEM analyses, it is confirmed that the grain size decreases with increased milling time. The value of the grain size observed from SEM is much larger than that observed from XRD analysis, which indicates that each particle observed by SEM consists of several crystallized grains. The reduction of the crystallite size ( D ) decreased the Curie temperature ( T C ) and magnetization values, and broadened the phase-transition region of the materials. The magnetocaloric effect was calculated in terms of the isothermal magnetic entropy change. The maximum value of the magnetic entropy change of the M0 sample, obtained from the M(μ 0 H) plot data, is | Δ S M max | = 1.35 J/kg K for an applied magnetic field of 5 T. In addition, the μ 0 H / M versus M 2 curves at temperatures around T C prove that the samples exhibit a second-order magnetic phase transition. The universal behavior obtained from the Δ S M variation curves confirmed the second-order transition for all the samples.