Temperature dependence of the bulk modulus of MgCNi3 in the normal state below room temperature
Hüsnü Özkan and Behiye Yüksel
Our previous article (Özkan, Philos. Mag. 2014) described a practical method to determine temperature dependence of the bulk modulus by using pressure dependence of the bulk modulus and the related analytical equations. The present study extended the method at low temperatures to obtain the bulk modulus of the superconducting peroxide MgCNi3 below room temperature. The bulk modulus of MgCNi3 decreases with temperature at a rate less than –0.008 GPa/K below 100 K, then it decreases at a higher rate, –0.020 GPa/K near 300 K, being close to corresponding theoretical values for the other non-oxide perovskites. Moreover, the Grüneisen parameter of MgCNi3 decreases from 300 K to 120 K, goes through a minimum and increases at lower temperatures. The thermal pressure, αVKT gradually increases from 1.1 MPa/K at 40 K to 2.0 at 100 K then, increases with slightly reduced rate to 4.9 MPa/K at 300 K being in reasonable agreement with the related data in the literature. This study verifies that the outlined method may be used to predict bulk moduli data below room temperature to substantiate the related studies.
Keywords: Bulk modulus, Grüneisen parameter, Thermal properties, Superconductors