Mechanisms of magnetoelectricity in manganese doped incipient ferroelectrics

TL;DR

This study investigates how manganese doping influences magnetoelectric properties in SrTiO3, revealing that magnetic interactions are mediated by specific Mn ions and proposing two microscopic coupling mechanisms.

Contribution

It provides new insights into the microscopic mechanisms of magnetoelectricity in manganese-doped incipient ferroelectrics, highlighting the role of Mn site distribution and proposing two coupling pathways.

Findings

Magnetization and resonance data show multiglass behavior affected by Mn site distribution.

Magnetic interactions are mediated by Mn_B^{4+} ions substituting Ti, as evidenced by theoretical calculations.

Two microscopic magnetoelectric coupling mechanisms are proposed involving spin-strain and exchange interactions.

Abstract

We report magnetization measurements and magnetic resonance data for SrTiO3 doped by manganese. We show that the recently reported coexistent spin and dipole glass (multiglass) behaviours are strongly affected by the distribution of Mn ions between the Sr and Ti sites. Motivated by this finding we calculate the magnetic interactions between Mn impurities of different kinds. Both LSDA+U and many-body perturbation theory evidence that magnetic and magnetoelectric interactions are mediated by Mn$_B^{4+}$ ions substituting for Ti. We propose two microscopic magnetoelectric coupling mechanisms, which can be involved in all magnetoelectric systems based on incipient ferroelectrics. In the first one, the electric field modifies the spin susceptibility via spin-strain coupling of Mn$_{B}^{4+}$. The second mechanism concerns Mn pairs coupled by the position-dependent exchange interaction.