d5 off-centering induced ferroelectric and magnetoelectric correlations in trirutile-Fe2TeO6

We present the rare existence of d⁵ off-centering induced weak ferroelectric polarization and demonstrate its correlation with observed magnetoelectric (ME) properties in the G type (T_N ∼ 210 K) antiferromagnet Fe₂TeO₆ (FTO) compound. The origin of ferroelectricity (FE) is associated with both lattice and asymmetric electron density (ED) distribution around the ion cores. ME coupling is observed in magnetic field-dependent polarization, ME voltage, and magnetostrain measurements. Short-range magnetic ordering due to intrabilayer dimeric exchange coupling via the double oxygen bridged Fe-O1-Fe pathway is proposed to play a dominating role to exhibit the negative nonlinear magnetic field-dependent ME behavior at 300 K. Interbilayer exchange via Fe-O2-Fe pathways dominantly determines the hysteretic nonlinear magnetic field-dependent ME response below T_N. The observed nonlinear ME coupling signifies magnetoelasticity as manifested in the temperature and magnetic field-dependent strain measurement. Hence, the rare existence of FE and magnetoelectric coupling by d⁵ ion is presented in FTO.