Large low field room temperature magneto-dielectric response from (Sr0.5Ba0.5)Nb2O6 / Co(Cr0.4Fe1.6)O4 bulk 3-0 composites

TL;DR

This study demonstrates a large magnetodielectric response at room temperature in bulk composites of Sr0.5Ba0.5Nb2O6 and Co(Cr0.4Fe1.6)O4, with optimal 30% magnetostrictive phase, highlighting the potential for magnetic field sensors.

Contribution

First demonstration of large room-temperature magnetodielectric coupling in Sr0.5Ba0.5Nb2O6/Co(Cr0.4Fe1.6)O4 composites with optimized phase fraction.

Findings

Maximum 3.2% dielectric change at 1000 Hz and 8000 Oe

Optimal magnetostrictive phase fraction is 30%

Coupling decreases beyond percolation threshold

Abstract

Bulk magnetodielectric composites with a 3/0 configuration comprising of ferroelectric/magnetostrictive phases have been synthesized using Sr0.5Ba0.5NbO6 / CoCr0.4Fe1.6O4 as the two constituents respectively. The ferroelectric phase made by a dual stage sintering process has a uniform grain size of 15 microns while the magnetostrictive phase has a grain size of 2 to 3 microns. Composites synthesized by conventional solid state processing using these two constituents exhibits large magnetodielectric coupling at room temperature which increases with increasing magnetic field. The composite with 30 percent magnetostrictive phase distributed uniformly in the ferroelectric phase has the most desirable microstructure and exhibits a large coupling with 3.2 percent change in the dielectric constant at 1000 Hz and 8000 Oe magnetic field. This change in dielectric constant decreases when the fraction of magnetostrictive phase is varied, indicating that 30 percent is the optimal value to realize large coupling between the two phases. This result confirms that 3D percolation causes the coupling to decrease in composites.