Growth of ZnO Mn/ZnO V Heterostructures and Ferroelectric-Ferromagnetic Characterization

The wide band gap semiconductor ZnO is well known for its multifunctionality in the form of ferromagnetism (FM) piezoelectricity and magneto optics ZnO has been found to grow with intrinsic oxygen deficiencies which in turn are believed to give ferromagnetism and high conductivity in this material Doping Zn2+ sites by V5+ ions creates a mixed valency as well as strain in the original ZnO hexagonal structure because of the reduced ionic size of vanadium The mixed valency creates charge polarity between Zn O and V O bonds This charge polarity and the rotation of the nonlinear V O bonds with respect to Zn-O bonds under electric field have been shown to produce ferroelectricity Furthermore Mn doping of ZnO has also shown enhancement in ferromagnetic properties in ZnO For this material to be a viable ferromagnetic material the magnetic properties should not be from segregated phases In the present study we have grown undoped Mn and V doped ZnO thin films using pulsed laser deposition (PLD) ZnO target with 2% atomic Mn doping and a target with 0 5% atomic V doping were prepared by solid state reactions and sintering Films were grown both epitaxially on sapphire substrates and in polycrystalline form on silicon substrates Magnetization measurements by the PPMS showed M vs H hysteresis loops with saturation for all ZnO Mn films V doped films showed high saturation polarization for film deposited at high pressures We have also fabricated epitaxial bilayers of ZnO V/ZnO Mn on sapphire substrates Ferroelectric and ferromagnetic properties of these heterostructures are presented