Spin-glass-like behavior and magnetocaloric properties in LaBiCaMn${}_2$O${}_7$ layered perovskite

The polycrystalline layered perovskite sample LaBiCaMn${}_2$O${}_7$ was synthesized by the conventional solid-state reaction process. By the X-ray powder diffraction, we have investigated the structural properties. The diffraction patterns are consistent with tetragonal lattice parameters a = 3.824 Å and c = 19.183 Å with I4/mmm as a space group. The magnetic measurements have demonstrated that their properties are relevant two magnetic transitions: first for a spin-glass (SG) transition at blocking temperature T${}_B$ = 76 K and a second for the ferromagnetic–paramagnetic transition is found at Curie temperature T${}_C$ = 225 K. The analysis of the Arrot diagram has shown the appearance of two transitions to be of the second-order type. The magnetic entropy variation (- ∆S${}_M$), induced by the magnetic field, was presumed on the basis of Maxwell relation. Under a change in a magnetic field of 2 T and around TC, the value of (- ΔS${}_M^{max}$) is found to be 4.17 J kg${}^{-1}$ K${}^{-1}$, and the value of RC (refrigeration capacity) is of 397 J.kg${}^{-1}$. It should be noted that LaCaBiMn${}_2$O${}_7$ displays a relatively prominent magnetocaloric effect at 225 K.