Electronic properties of (Ga,Mn)N thin films with high Mn content

MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington 6140, New Zealand
Journal of Applied Physics (Impact Factor: 2.18). 12/2008; 104(10):103710 - 103710-5. DOI: 10.1063/1.3020536
Source: IEEE Xplore

ABSTRACT Optical and dc resistivity measurements as well as x-ray spectroscopies have been performed on (Ga,Mn)N films containing Mn at up to 11 at . % . The results indicate that at higher Mn contents, the Fermi level is situated within extended states, while GaN host interband optical transitions are unaffected. The Mn state is confirmed to be 3d5 , as in the case of lower Mn content films; however, the high Mn content merges the 3d levels into a band located just below the host conduction band. The Fermi level is located within these Mn states just below the conduction band, in sharp contrast to its midgap position in fully crystalline, low Mn concentration materials. The difference in the position of the Fermi level at high Mn dopant levels has important implications for the promotion of ferromagnetism in this material.

Download full-text


Available from: Simon Granville, Sep 28, 2015
23 Reads
  • [Show abstract] [Hide abstract]
    ABSTRACT: We analyze the magnetic behavior of well-characterized, precipitate-free Ga1−xMnxN thin films containing Mn at higher levels than previously attained; up to x=0.36. This level is above the percolation threshold xc for nearest-neighbor cations, such that exchange between nearest neighbors will dominate the magnetic response. The susceptibility decreases as the Mn content increases up to and beyond xc, as an increasing fraction of the Mn experiences antiferromagnetic exchange. The dominance of antiferromagnetic behavior at higher Mn concentrations and the total lack of evidence for ferromagnetic ordering even above xc demonstrates that the nature of the exchange between Mn2+ ions in GaN is antiferromagnetic.
    Physical review. B, Condensed matter 05/2010; 81(18). DOI:10.1103/PhysRevB.81.184425 · 3.66 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We have performed first-principles calculations using the full-potential linearized augmented plane-wave method to investigate the magnetic properties of Al <sub>1-x</sub> Mn <sub>x</sub> N , Ga <sub>1-x</sub> Mn <sub>x</sub> N , and In <sub>1-x</sub> Mn <sub>x</sub> N semiconductors, for x=0.25 , 0.50, and 0.75 in their ordered zinc-blend ferromagnetic phase. For the structural properties, we found strong positive deviation from Vegard’s law regarding the variation in the lattice parameter which is in direct contrast with conventional III-V alloys. In addition, we found that In <sub>1-x</sub> Mn <sub>x</sub> N exhibits a half-metallic characteristic for all Mn composition. A total magnetic moment of 4 μ<sub>B</sub> was found for all In <sub>1-x</sub> Mn <sub>x</sub> N compositions, and for half-metallic phases of Al <sub>1-x</sub> Mn <sub>x</sub> N and Ga <sub>1-x</sub> Mn <sub>x</sub> N , respectively. The Mn atom is the main source of the total magnetic moment in these alloys, while the contributions from Al, Ga, In, and N are negligible.
    Journal of Applied Physics 01/2011; 108(12-108):123904 - 123904-7. DOI:10.1063/1.3524049 · 2.18 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The pure ZnO thin films were deposited by the wet chemistry (‘liquid ceramics’) method from the butanoate precursors on the single-crystalline (102) sapphire substrates. The films annealed in air (550 °C, 24 h) after butanoate pyrolysis have pronounced texture, and they reveal the ferromagnetic behaviour. Argon annealed films (650 °C, 30 min) exhibit randomly oriented grains, where the ferromagnetism of these non-textured films is almost equal to that of bare substrate. In both cases the films consist of dense equiaxial nanograins with size ∼20 nm. We observed that grain boundaries (GBs) and related vacancies are the intrinsic origin for RT ferromagnetism in polycrystals [Straumal et al., Phys. Rev. B 79, 205206 (2009)]. Present results demonstrate that not only the specific area of GBs in nanograined ZnO alone determines the ferromagnetic behaviour of ZnO. The GB character distribution (i.e. GB misorientation and orientation) is different in the textured and non-textured films. Most probably, the GBs with different character possess also different magnetic properties. The role of GBs, free surfaces and interfaces in ferromagnetic behaviour of GaN is discussed. In particular, their presence permits to increase the Mn solubility in GaN without precipitation of secondary ferromagnetic phases.
    physica status solidi (b) 07/2011; 248(7):1581-1586. DOI:10.1002/pssb.201001182 · 1.49 Impact Factor
Show more