Magnetoelectric P(VDF-HFP)-CoFe2O4 films and their giant magnetoresistance properties

Magnetoelectric (ME) nanocomposite flexible films composed of electroactive poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) and ferromagnetic cobalt ferrite (CoFe2O4) are fabricated. Single-phase nano CoFe2O4 with cubic spinel structure, synthesized by sol-gel auto combustion technique, is reinforced in different weight percentages to fabricate P(VDF-HFP)-CoFe2O4 films through spin coating technique. Effect of CoFe2O4 on structural, morphological, magnetic, ferroelectric, magnetoelectric properties, and giant magnetoresistance (GMR) behavior has been investigated. It is observed that the reinforcement of CoFe2O4 in P(VDF-HFP) matrix has strongly influenced the formation of beta-phase conformation and the degree of structural order. The co-existence of ferroelectric and ferromagnetic orderings in the films has been demonstrated by the P-E and M-H plots. The variations in the polarization effects in the presence of a magnetic field provide the evidence for magnetoelectric cross-coupling in P(VDF-HFP)-CoFe2O4. The films exhibit a GMR effect from 7% to 100%. In order to demonstrate the use of ME induced GMR in magnetic field sensing, P(VDF-HFP)-CoFe2O4 film (10 wt%) is used in a prototype sensor circuit. A good sensing ability and linear response obtained prove that the prepared film can be used as field sensor.