Mechanisms of magnetoelectricity in manganese-doped incipient ferroelectrics

Abstract

We report magnetization measurements and magnetic resonance data for SrTiO3\ndoped by manganese. We show that the recently reported coexistent spin and\ndipole glass (multiglass) behaviours are strongly affected by the distribution\nof Mn ions between the Sr and Ti sites. Motivated by this finding we calculate\nthe magnetic interactions between Mn impurities of different kinds. Both LSDA+U\nand many-body perturbation theory evidence that magnetic and magnetoelectric\ninteractions are mediated by Mn$_B^{4+}$ ions substituting for Ti. We propose\ntwo microscopic magnetoelectric coupling mechanisms, which can be involved in\nall magnetoelectric systems based on incipient ferroelectrics. In the first\none, the electric field modifies the spin susceptibility via spin-strain\ncoupling of Mn$_{B}^{4+}$. The second mechanism concerns Mn pairs coupled by\nthe position-dependent exchange interaction.\n