Structural and magnetic properties of La_0.72(Ca_1−xSr_x)_0.28MnO₃ (x = 0 to 1) manganites

Abstract

Polycrystalline manganites within the compositional variation La0.72(Ca1−xSrx)0.28MnO3 (x = 0, 0.25, 0.50, 0.75, 1.0) were synthesized by solid-state reaction method. An initial orthorhombic structure was observed at x = 0, with a subsequent change to rhombohedral structure for x ≥ 0.25. The Curie temperature of the compounds exhibited a marked dependence with the Sr content, with general variations between 190 K (x = 0) and 364 K (x = 1.0), while the saturation magnetization at room temperature showed a small variation between the range 0.30 and 0.38 T. The magnetocaloric effect, measured through heat capacity experiments, showed a maximum entropy variation of −2.56 J/kg · K at x = 0.25, besides a maximum adiabatic temperature variation of 1.13 K. Results are interpreted in terms of the structural transition observed and its effect on the radius of the A-site of the perovskite structure.

Magnetocaloric effect in La0.8Sr0.2MnO3 manganite

“…[6]. Moreover one may notice that, the RCP(S) of the sample studied is larger than for similar La 0.72 Sra 0.28 MnO 3 manganite, which exhibits the DS minimum around the Curie temperature of 364 K [7]. A width of para-to ferromagnetic transition and of DT peak is known to increase with raising atomic disorder.…”

“…On the other hand, for the La 0.75 Sr 0.25 MnO 3 manganite prepared by the sol-gel method [7], corresponding width at half minimum DT is about 41 K resulting in the RCP(S) about 55 J/kg, as estimated from Ref. [6].…”

Interface charge transfer in polypyrrole coated perovskite manganite magnetic nanoparticles

“…A significant increase of the saturation magnetizations, M S , for the LSMO@PPy composites as compared to the bare LSMO nanoparticles represents the second important fact as evidenced in the fourth column of Table II. Typical values of the saturation magnetization for polycrystalline Sr doped manganite (x ¼ 0.2À0.4), at room temperature, are within 40 -65 emu/g range, [26][27][28] while at lower temperatures (20 -50 K) they rise up to around 90 emu/g. [28][29][30] The increase of the saturation magnetization process arises as a direct result of PPy attachment to the nanoparticle surfaces.…”