Half Metallicity And Magnetic Properties Of Doped Chromium Oxide

In recent years,Cr O₂ has attracted much attention because of its wide application prospect and its special properties in spin electronic devices.But CrO₂ is metastable phase thermodynamics.There are still many problems need to be overcome for its successful application to the device.In this paper we combine theoretical calculation with experimental to explore the influence of various performance of Cr O₂ after doping,so that it can be more promising for the applications of spintronic devices.The main content of the paper are as follows:1,The electronic structure and anisotropy energy of Cr O₂ doped with Ti,Sn and Ru were calculated according to using first principle method.It was foud that high dopant concentration may be achievable for Ti or Ru-doped Cr O₂;while for Sn-doped CrO₂,the dopant concentration may be much lower.Half metallicity of CrO₂ will be intact when doped with Ti or Sn,but may be destroyed when doped with Ru,depending on Ru concentration and the relative positions of Ru ions.For Ti or Sn-doped Cr O₂,the MAC value decreases gradually with the increase of dopant concentration and also slightly depends on the relative positions of dopants,while the easy axis direction subjects to no change — always along [001] direction.However,as to Ru-doped Cr O₂,not only MAC value but also the easy axis direction shows strong dependence on both the concentration and the relative positions.2,CrO₂ thin films grown on different substrates were investigated.The stress in CrO₂ films depends on substrate.The CrO₂ films grown on the TiO₂?110?substrate have no stress,while those grown on TiO₂?110?/SnO₂ substrate will be stretched in the out of plane direction;As to the films grown on the TiO₂?100?/SnO₂ substrate,CrO₂ crystal is stretched in the in-plane direction and compressed in the out of plane direction.The study of magnetic properties find that,the easy axis coercivity of CrO₂ films grown on different substrates is increased with the decreasing of film thickness,but its the anisotropy is decreased with the decreasing of film thickness.The dependence of magnetic properties on the film orientation and substrate can be attributed to the variance of stress in the film.3,Sn doped CrO₂ thin films were fabricated on TiO₂?110?substrate.It is found that Sn doping may lead to a change of lattice constants;the lattice constants of CrO₂ seems not only to depend on doping concentration but also on thickness of the films.As to the magnetic properties,the introduction of Sn ions makes the domain wall pinning centers increase,which increases the coercive force of the easy axis;thesubstitution of no magnetic Sn4+ for Cr4+ leads to a decrease of the magnetization of the CrO₂ film.The investigation of hard axis loops of the films found that the switching field decrease after doped with Sn,indicating a decrease of magetocrystalline anisotropy of Cr O₂ after doping.With the increase of the Sn concentration,the coercivity of Sn doped film increase.It is also found that,the higher the Sn amount,the lower the magnetic anisotropy of the film,which is in agreement with our theoretical result.