Anomalous enhancement in the magnetoconductance of graphene/CoFe2O4 composite due to spin-orbit coupling

To understand the effect of charge transfer from the d-orbital of transition metal (TM) to the graphene p-orbital at the graphene/TM interface, magnetoconductance measurements have been carried out in graphene/CoFe2O4 composites over the temperature range from 20-300 K. A transition from positive to negative magnetoconductance is observed at 80 K. Below 80 K, magnetoconductance increases with decreasing temperature in the usual way; however, above 80 K it increases unusually with increasing temperature and reaches about 65% at 300 K. This anomalous enhancement in magnetoconductance at the higher temperature region has been explained on the basis of spin-orbit coupling acting at the interface. The nanocomposite containing large interfaces between graphene and CoFe2O4 nanoparticles exhibits a superior magnetodielectric effect with a 22% change in dielectric permittivity for an applied magnetic field of 1.8 T as a result of the combined effect between the Maxwell-Wagner polarization at the interface and a positive magnetoconductance of CoFe2O4.