Towards a new class of heavy ion doped magnetic semiconductors for room temperature applications

Abstract

The article presents, using Bi doped ZnO, an example of a heavy ion doped oxide semiconductor, highlighting a novel p-symmetry interaction of the electronic states to stabilize ferromagnetism. The study includes both ab initio theory and experiments, which yield clear evidence for above room temperature ferromagnetism. ZnBixO1−x thin films are grown using the pulsed laser deposition technique. The room temperature ferromagnetism finds its origin in the holes introduced by the Bi doping and the p-p coupling between Bi and the host atoms. A sizeable magnetic moment is measured by means of x-ray magnetic circular dichroism at the O K-edge, probing directly the spin polarization of the O(2p) states. This result is in agreement with the theoretical predictions and inductive magnetometry measurements. Ab initio calculations of the electronic and magnetic structure of ZnBixO1−x at various doping levels allow to trace the origin of the ferromagnetic character of this material. It appears, that the spin-orbit energy of the heavy ion Bi stabilizes the ferromagnetic phase. Thus, ZnBixO1−x doped with a heavy non-ferromagnetic element, such as Bi, is a credible example of a candidate material for a new class of compounds for spintronics applications, based on the spin polarization of the p states.

Bi-doping improves the magnetic properties of zinc oxide nanowires

“…Transition metals can be ferromagnetic themselves and when they are doped in oxide materials, for example, ZnO, can give rise to uncertainty in the origin of ferromagnetism in TM-doped nitrides and oxides, leading to complications in the growth of practical DMS materials. 1 This issue can be resolved by doping with a non-ferromagnetic element. 25 If these types of dopants and their oxides in the bulk form are non-ferromagnetic, then the formation of precipitates and clusters will probably not be the reason for the ferromagnetic behaviour of DMS-based materials.…”

Controlling room temperature ferromagnetism and band gap in ZnO nanostructured thin films by varying angle of implantation

“…40,41 As is evident from the XRD patterns, the ZnO:N60 has higher dislocation density and higher order of strains in the host lattice that results in the higher density of singly charged O vacancy defects and hence, introduces the stronger polarization eld. 42,43 This higher density of V o defects states produces the higher order of unpaired states and most probably results in the higher order of ferromagnetism at room temperature in ZnO:N60 nanostructured thin lms. Further, the ferromagnetism diminishes in ZnO:N30 not only due to the low strain but also increase in the local temperature during implantation.…”

Polarity Control of ZnO Films Grown on Ferroelectric (0001) LiNbO3 Substrates without Buffer Layers by Pulsed-Laser Deposition

“…Together with the growth of the ZnO films, the polarity determination of the ZnO films was investigated for various device applications. The material properties of the host material, ZnO, are sound, and many of the potential applications for optoelectronics [17,18] and spintronics [19] can be employed together with gallium nitride (GaN). A key bottleneck regarding the polarity control of ZnO films is the polarity-controlled crystallization in the facile method.…”