Magnetoelectric and magnetodielectric coupling and microwave resonator characteristics of Ba 0.5 Sr 0.5 Nb 2 O 6 /CoCr 0.4 Fe 1.6 O 4 multiferroic composite

摘要

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.