Large magnetocaloric effect in Ln_0.5Ca_0.5MnO₃ (Ln=Gd, DY) compounds: Conseqence of magnetic precursor effect of rare earth ions

Magnetic, specific heat and magnetocaloric studies have been performed on rare earth calcium manganites; Ln_0.5Ca_0.5MnO₃ (Ln=Gd, Dy). The observed isothermal magnetic entropy change is fairly large at low temperature in the manganites family, which is attributed to the magnetic precursor effect of rare-earth ions. For Gd_0.5Ca_0.5MnO₃, the isothermal magnetic entropy change (−ΔS) at 4 K, obtained for 7 T magnetic field, is as high as 22.8 J/kg K. On the other hand, −ΔS is 8.5 J/kg K for Dy_0.5Ca_0.5MnO₃. The large value of magnetic entropy change at the cryogenic temperature range for these compounds is interesting from application point of view. - Highlights: • No long range magnetic ordering of Gd_0.5Ca_0.5MnO₃ and Dy_0.5Ca_0.5MnO₃ has been observed in magnetization measurement down to T=2 K still these compounds show large magnetocaloric effect. • Specific heat of the compounds in absence of magnetic field increases at low temperature (down to 3 K). • Results are analyzed considering magnetic precursor effect of rare earth ions (Gd and Dy ions)