Bulk modulus and thermodynamic properties of electron-doped calcium manganate—Ca 1−xRE xMnO 3

Abstract

We have investigated the thermodynamic properties of electron-doped perovskite manganite CaMnO 3 by incorporating the effect of lattice distortions. In this paper the functional relation between the MnO 6 distortions, charge and size mismatch and the thermal properties is determined. In the insulating state, distortions of the Mn–O environment are linear with calcium concentration. In the low-temperature spin-ordered ferromagnetic/anti-ferromagnetic state, at least 50% of the distortion is removed. The lattice contributions to the specific heat at constant volume ( C v (lattice)) of Ca 1− xRE x MnO 3 ( x=0.05, 0.1, 0.15, 0.20) with rare earth cation doping at the A-site has been studied as a function of temperature (10 K≤ T≤500 K) by means of a Modified Rigid Ion Model (MRIM). In addition, the results on the bulk modulus ( B), cohesive energy ( φ), molecular force constant ( f), Reststrahlen frequency ( ν 0) and Gruneisen parameter ( γ) are also presented. Findings indicate an anomalous behavior of some highly Jahn–Teller (JT) distorted Ca 1− xRE x MnO 3.