Relaxor ferroelectric behavior and intrinsic magnetodielectric behavior near room temperature in Li2Ni2Mo3O12, a compound with distorted honeycomb and spin-chains

TL;DR

This study reports that Li2Ni2Mo3O12 exhibits relaxor ferroelectricity between 160-240 K and shows intrinsic magnetodielectric effects near room temperature, linked to structural disorder and magnetic interactions.

Contribution

It demonstrates intrinsic magnetodielectric behavior near room temperature in a complex oxide with relaxor ferroelectricity, a novel finding for this material class.

Findings

Relaxor ferroelectricity observed between 160-240 K.

Magnetodielectric effect of about -2.4% at 300 K.

Crystallographic disorder linked to relaxor behavior.

Abstract

Keeping current interests to identify materials with intrinsic magnetodielectric behavior near room temperature and with novel pyroelectric current anomalies, we report temperature and magnetic-field dependent behavior of complex dielectric permittivity and pyroelectric current for an oxide, Li2Ni2Mo3O12, containing magnetic ions with (distorted) honey-comb and chain arrangement and ordering magnetically below 8 K. The dielectric data reveal the existence of relaxor ferroelectricity behavior in the range 160-240 K and there are corresponding Raman mode anomalies as well in that temperature range. Pyrocurrent behavior is also consistent with this interpretation, with the pyrocurrent peak-temperature interestingly correlating with the poling temperature. 7Li NMR offer an evidence for crystallographic disorder intrinsic to this compound and we therefore conclude that such a disorder is apparently responsible for the randomness of local electric field leading to relaxor ferroelectric property. Another observation of emphasis is that there is a notable decrease in the dielectric constant with the application of magnetic field to the tune of about -2.4% at 300 K, with the magnitude varying mariginally with temperature. Small loss factor values validate intrinsic behavior of the magnetodielectric effect at room temperature.