Theoretical Investigation of the Magnetoelectric Properties of Bi2NiTiO6

TL;DR

This study uses first-principles calculations to explore the structural, electronic, magnetic, and ferroelectric properties of Bi2NiTiO6, revealing its potential as a multiferroic material with strong magnetoelectric coupling.

Contribution

It provides the first theoretical investigation of Bi2NiTiO6's properties, highlighting the role of spin state transitions and covalency in its multiferroic behavior.

Findings

Bi2NiTiO6 is an insulator with G-type magnetic ordering.

Spin state transition influences magnetoelectric coupling.

Polarization of 32 μC/cm² due to covalency and lone pairs.

Abstract

We report the first principle investigations on the structural, electronic, magnetic and ferroelectric properties of a Pb free double perovskite multiferroic Bi2NiTiO6 using density functional theory within the general gradient approximation (GGA) and GGA+U method. Our results show that Bi2NiTiO6 will be an insulator with G-type magnetic ordering in its ground state with Ni2+ in a high spin state and a spin moment of 1.74\mu_B. The paraelectric phase stabilizes in nonmagnetic state with Ni2+ in low spin configuration showing that spin state transition plays an important role in strong magnetoelectric coupling in Bi2NiTiO6. The bonding characteristics of the constituents are analyzed with the help of partial density of states and Born effective charges. The presence of Ti ions at Ni sites suppresses the disproportionation observed in case of BiNiO3 and results in a noncentrosymmetric crystal structure. The coexistence of Bi 6s lone pair and Ti4+ d0 ions which brings covalency produces a polarization of 32 \muCcm-2.