Magnetoelectric and magnetodielectric coupling and microwave resonator characteristics of Ba0.5Sr0.5Nb2O6/CoCr0.4Fe1.6O4 multiferroic composite

Abstract

A multiferroic composite consisting of single phases of 30 vol.% magnetostrictive ferrite and 70 vol.% relaxor ferroelectric has been synthesized. The ferrite exhibits a diffuse dielectric phase transition (DPT)with the transition temperature varying from 450 K to 600 K and an activation energy of 0.29 eV. Magnetically, it has a soft behavior with 70 emug⁻¹ saturation magnetization and a Curie transition at ~620 K. The relaxor ferroelectric phase on the other hand exhibits two clear DPTs at 390 K–400 K and 150 K–300 K. The composite of these two shows a soft ferromagnetic behavior reminiscent of the ferrite along with 3 DPTs. There is strong coupling between the two orders – magnetostrictive and piezoelectric in the composite. The capacitance decreases by 45% in the presence of magnetic field corresponding to a sensitivity of 0.9% kOe⁻¹, an extremely large value. The magnetoelectric coupling constant is found to be 20.6 mVcm⁻¹Oe⁻¹, a large value for a bulk composite. Microwave band stop filters of different thicknesses made from the composite have resonant frequencies which upshift in the presence of magnetic field indicating a multiferroic behavior with possibility for electric field tuning of resonant frequency.