Tracking defect-induced ferromagnetism in GaN:Gd

Roever, M.; Malindretos, J.; Bedoya-Pinto, Amílcar; Rizzi, A.; Rauch, Christian; Tuomisto, Filip

doi:10.1103/physrevb.84.081201

Cited by 44 publications

(39 citation statements)

References 24 publications

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“…A fundamental question is whether materials containing only s or p electrons can be ferromagnetic. For nearly two decades, there have been various theoretical and experimental studies devoted to clarifying this question [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. It turns out that materials with completely filled 3d or 4f shells or with only s or p electrons can be ferromagnetic when they contain defects.…”

Section: Introductionmentioning

confidence: 99%

Defect-induced magnetism in SiC: Interplay between ferromagnetism and paramagnetism

et al. 2015

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Defect-induced ferromagnetism has triggered a lot of investigations and controversies. The major issue is that the induced ferromagnetic signal is so weak that it can sufficiently be accounted for by trace contamination. To resolve this issue, we studied the variation of the magnetic properties of SiC after neutron irradiation with fluence covering four orders of magnitude. A large paramagnetic component has been induced and scales up with defect concentration, which can be well accounted for by uncoupled divacancies. However, the ferromagnetic contribution is still weak and only appears in the low fluence range of neutrons or after annealing treatments. First-principles calculations hint towards a mutually exclusive role of the concentration of defects: a higher defectconcentration favors a larger magnetic interaction at the expense of spin polarization. Combining both experimental and first-principles calculation results, the defect-induced ferromagnetism can probably be understood as a local effect which cannot be scaled up with the volume. * Electronic address: s.zhou@hzdr.de 2

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Section: Introductionmentioning

confidence: 99%

Defect-induced magnetism in SiC: Interplay between ferromagnetism and paramagnetism

et al. 2015

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“…[10][11][12][13] The acceptor-like defects can have important duality-they are not only fairly localized but also have extended tails that could allow for long-ranged magnetic coupling. Experimental investigations of the role of intrinsic defects in the magnetic ordering observed in wide band-gap semiconductors are scarce, 14,15 as most of the research has been based on electronic structure calculations. Defect related magnetic phenomenon is an important issue involved in high effective moment and room temperature ferromagnetism observed recently in GaN:Gd samples.…”

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confidence: 99%

“…Defect related magnetic phenomenon is an important issue involved in high effective moment and room temperature ferromagnetism observed recently in GaN:Gd samples. 15 Further, in order to be certain of studying only the magnetic effects produced by intrinsic defects, they need to be introduced in a controlled way, e.g., through particle irradiation. 16 In this work, we investigate the magnetic properties of 3 lm-thick GaN layers grown by metal-organic chemical-vapor deposition (MOCVD) on sapphire substrates with point defects controllably created via high energy He irradiation, as measured by Tuomisto et al in Ref.…”

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confidence: 99%

Magnetically active vacancy related defects in irradiated GaN layers

et al. 2012

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We present the studies of magnetic properties of 2 MeV 4He+-irradiated GaN grown by metal-organic chemical-vapor deposition. Particle irradiation allowed controllable introduction of Ga-vacancy in the samples. The magnetic moments with concentrations changing between 4.3...8.3x10^17 cm^-3 showing superparamagnetic blocking at room temperature are observed. The appearance of clear hysteresis curve at T = 5 K with coercive field of about H_C = 270 Oe suggests that the formation of more complex Ga vacancy related defects is promoted with increasing Ga vacancy content. The small concentration of the observed magnetically-active defects with respect to the total Ga- vacancy concentration suggests that the presence of the oxygen/hydrogen-related vacancy complexes is the source of the observed magnetic moments.Comment: 3 pages, 3 figure

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“…It was shown in Thiess et al 27 that vacancy clusters can arise during growth if the optimized surface distribution of vacancies becomes frozen in. Furthermore evidence for vacancy clusters can be found in positron annihilation studies of Roever et al 28 .…”

Section: 24mentioning

confidence: 75%

Systematic study of the exchange interactions in Gd-doped GaN containing N interstitials, O interstitials, or Ga vacancies

et al. 2015

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Using large supercells models and the KKRnano multiple scattering approach, statistically meaningful information is obtained on the distribution of local densities of states, magnetic moments and distance dependent exchange interactions for interstitial N or O or Ga-vacancies in Gd-doped GaN. The exchange interactions between N-interstitials (Ni) and Ni with Gd are found to be shortranged and mainly antiferromagnetic, while exchange interactions between Gd are negligible. For O-interstitials, the ferro-and antiferromagnetic interactions between Gd and Oi are roughly cancelling each other, and the Oi-Oi interactions are ferromagnetic but very short-ranged. The Fermi level dependence of these interactions is studied. The difference between Ni and Oi behavior is related to the filling of up and down spin partial densities of states, which promotes antiferromagnetic super-exchange and ferromagnetic double exchange for Ni and Oi respectively. On the other hand, Ga-vacancies provide significantly stronger and more robust ferromagnetic interactions between moments localized on N near the vacancies and may reach the percolation threshold for concentrations of order 5 %. The role of strain in films grown under different conditions on the vacancy concentration is discussed.

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Tracking defect-induced ferromagnetism in GaN:Gd

Cited by 44 publications

References 24 publications

Defect-induced magnetism in SiC: Interplay between ferromagnetism and paramagnetism

Defect-induced magnetism in SiC: Interplay between ferromagnetism and paramagnetism

Magnetically active vacancy related defects in irradiated GaN layers

Systematic study of the exchange interactions in Gd-doped GaN containing N interstitials, O interstitials, or Ga vacancies

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