Intrinsic versus extrinsic ferromagnetism inHfO2−xandNi:HfO2−

Abstract

We have investigated the possible evolution of an intrinsic stable ferromagnetic moment in oxygen deficient undoped and magnetically doped HfO 2−x thin films grown by reactive molecular beam epitaxy. Neither oxygen vacancies nor substituted Ni in combination with such vacancies results in an observable magnetic moment for a broad range of oxygen vacancy concentrations. By combining integral and element specific magnetization measurements, we show that a fluctuating deposition rate of the magnetic dopant induces extrinsic ferromagnetism by promoting the formation of metallic clusters. We suggest the element specific measurement of an induced magnetic moment at the nonmagnetic site as a proof of intrinsic ferromagnetism in diluted magnetic semiconductors.

Defect energetics of cubic hafnia from quantum Monte Carlo simulations

“…The reported total magnetic moment is 1.0 µ B per N defect. In contrast, a study by Hildebrandt et al 15 , taking into account a broad range of oxygen vacancy concentrations and magnetic dopants, has shown that undoped, oxygendeficient, or magnetically doped hafnia does not possess intrinsic ferromagnetism.…”

“…A lower than ideal performance in electronic gates can be explained by the formation of defect-related fixed charges 13,14 . The monoclinic phase has been well studied both experimentally via scattering techniques 15,16 , and theoretically using DFT 4,[17][18][19] . Moreover, first-principles calculations carried out on the low-temperature monoclinic phase of hafnia with oxygen vacancies and oxygen interstitials suggest that the oxygen vacancies represent the main electron traps 18 .…”

Room-temperature ferromagnetism of 2H-SiC-α-Al2O3solid solution nanowires and the physical origin

“…11 Recently, both the physical origin and the experimental phenomenon have been investigated widely on a number of semiconductor materials such as ZnO, TiO 2 , MnO 2 , HfO 2 and SnO 2 . 12,[13][14][15][16] Frequently, intrinsic defects emerging in the crystal account for the magnetic behavior in most of the undoped materials. The high-spin defect state formed by isolated defects would be coupled ferromagnetically with a shortrange magnetic interaction creating a ferromagnetic ground state.…”