Comparison of the structural and magnetic properties of ground-state SrTcO3 and CaTcO3 from first principles

The generalized gradient approximation (GGA) plus on-site Coulomb interaction corrections (GGA+U) method is employed for the total energies and electronic structure calculations of SrTcO3 and CaTcO3. G-type antiferromagnetic (G-AFM) is found to be ground state for both compounds, in consistence with the previous experimental results. The mechanism of Neel temperature of SrTcO3 being higher than that of CaTcO3 is explored. The insulating band gaps of SrTcO3 and CaTcO3 are found to be 1.71 eV and 1.74 eV, respectively. The magnetic moment of Tc1 is found to be 2.237μB2.237μB in SrTcO3 unit cell and 2.266μB2.266μB in CaTcO3 unit cell. Structural parameters and electronic structure of the two compounds are examined to explore the origin of their different electrical and magnetic characters.