Elastic behavior of magnetic systems with a narrow twofold-degenerate band.

Abstract

The modification of the effect of electron-lattice interaction on the shear modulus C'=(1/2(${C}_{11}$-${C}_{12}$) in itinerant magnetic systems with the Fermi energy lying on a narrow twofold-degenerate band is investigated on the basis of the Hartree-Fock approximation of the degenerate Hubbard Hamiltonian. The softening of the elastic constant due to the electron-lattice interaction at T=0 is more for weakly magnetic (ferro- or antiferromagnetic) systems compared to the case of saturated moment systems. As T approaches ${T}_{c}$ (or ${T}_{N}$) the elastic constant C' decreases sharply and the amount of decrease is larger for the saturated ferromagnetic (or antiferromagnetic) system than that for the weakly magnetic system. These results are found to be sensitive functions of the interorbital exchange. In the paramagnetic phase, the electronic contribution to C' depends on the density of states at the Fermi energy and is weakly temperature dependent. These results are discussed in light of the elastic anomalies of C' in bcc iron.