Ferromagnetism in CuO-ZnO multilayers

We investigated the magnetic properties of CuO-ZnO heterostructures to elucidate the origin of the ferromagnetic signature in Cu doped ZnO. The CuO and ZnO layer thickness were varied from 15 to 150 nm and from 70 to 350 nm, respectively. Rutherford backscattering experiments showed no significant diffusion of either Cu in ZnO or Zn in CuO layers. Magnetic measurements indicate ferromagnetism at 300 K, which depends on the CuO particle size, but not on the CuO-ZnO interfacial area. Polarized neutron reflectometry measurements show that the observed magnetization cannot be accounted for solely by spins localized near the CuO-ZnO interface or in the CuO layer. (C) 2008 American Institute of Physics.