Magnetocaloric study of La0.45Nd0.25Sr0.3MnO3/ MO (MO=CuO, CoO and Ni) nanocomposites

Abstract

Recently, solid-state magnetic refrigeration (MR) technique has great interest of research as a promising technology based on magnetocaloric effect to replace the conventional cooling techniques. Many literature reviewed La0.45Nd0.25Sr0.3MnO3/5%CuO composite shows convincing magnetocaloric properties. The present study investigate the detail magnetocaloric study of La0.45Nd0.25Sr0.3MnO3/ x Wt% (M)O, (x=0.0, 0.25, and 0.50, M = Cu, Co and Ni) nano-composite samples. Pure phase exchange coupled nanocomposites of magnetically soft oxides were prepared via one-pot autocombustion method and heat treated in air at 1100OC for 12 h. The influence of wt% of transition metal oxide to the composite on the structural, morphology, magnetic and magnetocaloric properties have been investigated using X-ray diffraction, SEM and SQUID.XRD pattern of the composite reveals the presence of a distinct pure and single-phase rhombohedral structure of perovskite-based material La0.45Nd0.25Sr0.3MnO3(LNSMO) with space group R-3c and monoclinic structure of metal oxide(MO) with the ICCD numbers (LNSMO: 01-082-1152). No trace of secondary phase was detected within the sensitivity limit of the experiment. Rietveld refinement was performed using fullprof software to calculate prepared sample’s mass ratio, lattice parameter and cell volume. The lattice parameters aren’t much effected due to presence of very small amount of metal oxide and values are matched with published literature. The SEM techniques were used to identify the obtained nano-structural morphologies. The NiO/CoO/CuO material were located at the grain boundaries with uniform homogeneity due to the uniaxial pressure effect.Temperature dependence of field-cooled (FC) curve exhibits second-order transition with Tc near room temperature. The temperature depending of magnetization as a function of applied field for all the samples set were measured and conformed the paramagnetic behavior above the transition temperature and ferromagnetic behavior below the transition temperature. The isothermal magnetic entropy change (ΔSm) was calculated to evaluate the magnetocaloric property of the material. The ΔSm have a maximum value around the vicinity of the transition temperature and decrease with any further increase of the temperature. The maximum value of ΔSm for 5T field were found near room temperature. All the values of ΔSm are higher than ferrites oxides. The reason could be the grain size and particle distribution. The uniform distribution of NiO and CoO particles in the grain boundaries than CuO gives the enhance value of entropy change with CoO and NiO compare to CuO. Also, the grain size of La0.45Nd0.25Sr0.3MnO3 for CoO has higher as compare to CuO. This is the effectiveness of one pot autocombustion technique in achieving effective growth of fine grains of respective phases. Cooling efficiency can be calculated from the peak position of ΔSM called relative cooling power (RCP). RCP values of our nanoparticle samples being the maximum for 5wt%CoO. These results make our compounds promising materials for magnetic refrigeration technology. Our study suggests that the La0.45Nd0.25Sr0.3MnO3/ x Wt% (A)O, (x=0.0, 0.25, and 0.50, A = Cu, Co and Ni) nano-composite materials with various morphologies could exhibit interesting magnetocaloric properties near room temperatures **