Eur. Phys. J. B 78, 531-534 (2010)
https://doi.org/10.1140/epjb/e2010-10601-3

First-principle study of the electronic structure and magnetism in RuSr₂GdCu₂O₈ under pressure

Magnet Research Laboratory (MRL), Department of Physics, Sharif University of Technology, P.O. Box 11365, -9161, Tehran, Iran

Corresponding author: ^a akhavan@sharif.edu

Received: 3 August 2010
Published online: 6 December 2010

Abstract

We have performed a first-principle calculation of the structural, electronic and high pressure properties of RuSr₂GdCu₂O₈, a ferromagnetic superconductor, by employing a full-potential linearized augmented plane-wave method within the density-functional theory. The effect of pressure was achieved by varying the volume of the unit cell with constant a:b:c ratio. The experimentally observed anti-phase rotation of RuO₆ octahedra has been attributed to the residual forces on O_Ru which results in shear strain in the RuO₂ layer. Partial charge analysis shows that applying pressure up to 6 GPa leads to hole creation in the CuO₂ sheets which causes increase in the superconducting transition temperature. We have estimated the Curie temperature T_M of this compound in the mean-field approximation using Heisenberg model with first-nearest neighbor exchange interactions determined from DFT calculations for parallel and anti-parallel spin configurations of Ru moment in RuO₂ planes. The effect of pressure causes the magnetic moment of Ru atoms to decrease due to the increase of hybridization between the adjacent Ru atoms. The calculated exchange splitting in Cu d_x2-y2 states increases slightly with pressure but it is still very small that it does not affect superconductivity, and the hole doping mechanism is dominant.