Tuning the giant Magnetocaloric Effect and refrigerant capacity in Gd_1–xY_xCrO₃ (0.0 ≤ x ≤ 0.9) perovskites nanoparticles

Different compounds of rare-earth orthochromites Gd_1–xY_xCrO₃ (where x is 0.0–0.9) powder nanoparticles, were synthesized by the auto-combustion method followed by annealing at 700 ℃. All the compounds showed single-phase and crystallized into a distorted orthorhombic structure with the space group (Pbnm). The average particle size for all the samples were in the range 53–110 nm. The detailed and systematic magnetic measurements and analysis showed that all the samples up to x = 0.9 have large magnetization and large values of the change in the magnetic entropy. The magnitude of the change in the magnetic entropy (at 4.5 K and for all the values of the change in the applied magnetic field between 1 and 9 T) is found to increase with increasing x reaching a maximum value at x = 0.3 then it decreases as we increase the yttrium concentration. The nanoparticle compounds with low yttrium concentrations showed a giant change in the magnetic entropy and a giant relative cooling power. Based on the slopes of Arrott plots curves the order parameter of the magnetic transition has been estimated and found to be second order. The giant change in the magnetic entropy and the relative cooling power were tuned in the rages (-45.6 to -8.7 J/kg·K at a change in the applied magnetic field of 9 T; and 136–746 J/kg), around the helium liquefaction temperature. The magnitude of the change in the magnetic entropy is significantly larger for large range of temperatures, up to the nitrogen liquefaction temperature. The giant change in the magnetic entropy and the giant relative cooling power at low temperatures (in the range about 4 to 20 K.) make these samples candidate materials for the low temperature magnetic refrigerant applications, based on the magnetocaloric effect.