Till Örebro universitet

The critical temperature T_C of ferromagnetic La_xSr_1−xMnO₃ (LSMO) can be controlled by distorting the crystal structure, as was reported by Thiele et al (2007 Phys. Rev. B 75 054408). To confirm these findings theoretically, we investigate the electronic as well as the magnetic ground state properties of La_2/3Sr_1/3MnO₃ as a function of tetragonal lattice distortions, using a multiple-scattering Green function method. Within this approach, we calculate exchange coupling constants as well as the phase transition temperature from first principles. Comparing our findings with those for La_2/3Sr_1/3CoO₃ (LSCO), we find that the decrease of T_C is much stronger in LSMO than in LSCO. Our findings can be explained by the electronic structures and are also in accordance with the experiment. The computed decrease of T_C with distortion is smaller than observed experimentally, a result that corroborates the importance of phonon contributions.