The Effect of Potassium Doping on Specific Heat of Rare Earth Manganite RMnO3(R=La, Pr).

Abstract

We probe the  physical properties of rare earth manganites R_1−xK_xMnO₃(R=La, Pr) like thermal expansion and Specific heat for their possible use as magnetic refrigerant material. Effect of Potassium doping (K⁺ at the A-site) on the thermal properties of perovskite RMnO₃ has been considered in this investigation using the Modified Rigid Ion Model (MRIM)). The specific heat of magnetocaloric compounds La_1−xK_xMnO₃­, and Pr_1−xK_xMnO₃­ as a function of temperature (20K≤T≤1000K) is reported. In addition, the results on the cohesive energy (f), molecular force constant (¦), Reststrahlen frequency (n_o), Debye temperature (Q_D) and Gruneisen parameter (g) are also discussed. The monovalent cation (K⁺) doping results in anomalous change in Debye temperature for heavily doped La_1−xK_xMnO₃­ beyond x=0.5. The Specific heat decreases with increase in content of potassium doping in La_1−xK_xMnO₃ compound and it comes to a minimum for x=0.5 and then specific heat increases with further increase in doping concentration of Potassium in the LaMnO₃.­

Keywords: Specific Heat, Magnetocaloric compounds, Thermal Properties, Bulk modulus, Colossal Magnetoresistance material, Manganites.