Bulk modulus and thermodynamic properties of electron-doped calcium manganate—Ca1−xRExMnO3

We have investigated the thermodynamic properties of electron-doped perovskite manganite CaMnO3 by incorporating the effect of lattice distortions. In this paper the functional relation between the MnO6 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 (Cv(lattice)) of Ca1−xRExMnO3 (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 (ν0) and Gruneisen parameter (γ) are also presented. Findings indicate an anomalous behavior of some highly Jahn–Teller (JT) distorted Ca1−xRExMnO3.