Normal and superconducting state specific heat of Mg_1 − xAl_xB₂(0 < x < 0.2)

Abstract

A theoretical analysis of specific heat C(T) behaviour of the Mg 12x Al x B 2 (0 , x , 0.2) in the temperature domain 0 # T # 300 K is presented. Calculations of C(T) have been made within the two-component scheme: one is the phonon and the other is the electronic contribution. Phonon specific heat is well estimated from the Debye and Einstein temperature for Mg 12x Al x B 2 obtained following an overlap repulsive potential. The interatomic potential of this model includes contributions from the long-range Coulomb attraction and the short-range overlap repulsion and the van der Waals attraction. The fermion constituent as the electronic specific heat is deduced using a suitable trial function above and below T c . At the critical temperature, the discontinuity in specific heat is higher than that of other samples and the transition is sharper than for most samples. The theoretical results from boson and fermion terms are then compared with the experimental results.