Magnetodielectric effect of Bi6Fe2Ti3O18 film under an ultra-low magnetic field

TL;DR

This study demonstrates that Bi6Fe2Ti3O18 ferroelectric films exhibit a significant magnetodielectric response under ultra-low magnetic fields, with effects varying notably across different temperature ranges due to magnetic phase transitions.

Contribution

The paper reports the first observation of ultra-low magnetic field-induced magnetodielectric effects in Bi6Fe2Ti3O18 films, highlighting potential for low-cost magnetic field sensors.

Findings

Magnetodielectric response of 0.05 at T<55K

Maximum MD of -0.14 between 55K and 190K

Effect linked to magnetic phase transitions

Abstract

Good quality and fine grain Bi6Fe2Ti3O18 magnetic ferroelectric films with single-phase layered perovskite structure have been successfully prepared via metal organic decomposition (MOD) method. Results of low-temperature magnetocapacitance measurements reveal that an ultra-low magnetic field of 10 Oe can produce a nontrivial magnetodielectric (MD) response in zero-field-cooling condition, and the relative variation of dielectric constants in magnetic field is positive, i.e., MD=0.05, when T<55K, but negative with a maximum of MD=-0.14 when 55K<T<190K. The magnetodielectric effect appears a sign change at 55K, which is due to transition from antiferromagnetic to weak ferromagnetic; and vanishes abruptly around 190K, which is thought to be associated with order-disorder transition of iron ion at B site of perovskite structures. The ultra-low-field magnetodielectric behaviour of Bi6Fe2Ti3O18 film has been discussed in the light of quasi-two-dimension unique nature of local spin order in ferroelectric film. Our results allow expectation on low-cost applications of detectors and switches for extremely weak magnetic fields in a wide temperature range 55K-190K.