Tailoring large magnetodielectric response in core/shell CrO2/Cr2O3 nano-rods

Ferromagnetic/antiferromagnetic CrO2/Cr2O3 core/shell nano-rods were fabricated where the Cr2O3 outer shell was structurally and chemically tailored by controlling the decomposition of the CrO2 core. The dielectric response and magnetodielectric effect (MDE) were studied with respect to the thickness of the dielectric Cr2O3 layer. A giant dielectric constant of similar to 10(4), resulting from space charge polarization, is induced by the accumulation of free charges at the interface of the conducting CrO2 and the insulting Cr2O3 nanostructure. An enhanced MDE (Delta epsilon'/epsilon' = 3.5%), appearing at the dielectric relaxation frequency, stems from the change of dielectric dispersion under the application of a magnetic field of H = 2400 Oe when the thickness of Cr2O3 shell is similar to 6.0 nm. We submit that the MDE is due to the interface electric dipole coupled by ferromagnetic spins at the interface of the ferromagnetic CrO2/antiferromagnetic Cr2O3 heterostructures. (C) 2016 Elsevier B.V. All rights reserved.