Effect of Ga substitution on magnetocaloric effect in La0.7(Ba, Sr)0.3Mn1−xGaxO3 (0.0≤x ≤0.20) polycrystalline at room temperature

• The manganites phases crystallize in an orthorhombic (Pnma) structure.
• The samples exhibit a second order PM–FM phase transition at room temperature.
• All samples are potential candidates for room-temperature magnetic refrigeration.
• The universal curves confirmed that the magnetic transition is of a second order.

In this paper, we have investigated the effect of the non-magnetic (d10) Ga3+ doping on structural, magnetic and magnetocaloric properties of La0.7(Ba, Sr)0.3Mn1−xGaxO3 (x=0.0, 0.1 and 0.2) manganites prepared by solid state reaction method. The XRD study has revealed that all samples crystallized in the orthorhombic symmetry with Pnma space group. Magnetization measurements have confirmed that when the temperature increases, all the compositions exhibit a ferromagnetic to paramagnetic transition. The substitution of Mn by gallium Ga leads to a tune of the magnetic transition temperature (TC) to room temperature and the Curie temperature decreases from 314 K for x=0.0 to 299 K for x=0.2. Moreover, the obtained results of the magnetocaloric effect are in accordance with the reported values of other doped manganites, leading to the conclusion that our sample can be used as a magnetic refrigerant at room temperature.Finally, using Arrott plots, the phase transition from ferromagnetic to paramagnetic was found to be of a second order. The second order magnetic phase transition has been confirmed by the construction of the universal curve of the magnetic entropy change.

Temperature dependence of the magnetization measured at μ0μ0H=0.05 T for La0.7(Ba, Sr)0.3Mn1−xGaxO3 (x=0.0, 0.1 and 0.2) compounds. The a-inset indicates the dM/dT (T) curves used to determine TC and the b-inset shows the temperature dependence of the inverse magnetic susceptibility at µ0H=0.05 T.Figure optionsDownload as PowerPoint slide