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

Abstract

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 CoFe₂O_4.