Origin of the high Néel temperature in SrTcO3.

We investigate the origin of the high Néel temperature recently found in Tc4+ perovskites. The electronic structure in the magnetic state of SrTcO3 and its 3d analogue SrMnO3 is calculated within a framework combining band-structure and many-body methods. In agreement with experiment, for SrTcO3 a smaller magnetic moment and 4 times larger Néel temperature are found. We show that this is because the Tc compound lies on the verge of the itinerant-to-localized transition, while the Mn compound lies deeper into the localized side. For SrTcO3 we predict that the Néel temperature depends weakly on applied pressure, in clear violation of Bloch's rule, signaling the complete breakdown of the localized picture.