Dilute Magnetic Oxides and Nitrides

Coey, J. M. D.; Rode, Karsten

doi:10.1002/9780470022184.hmm405

Cited by 7 publications

(5 citation statements)

References 82 publications

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“…On the other hand, it has been demonstrated that ZnO doped with rare-earth ions can also create ferromagnetism at room temperature [20]. The magnetic property of the transition metal or rare earth elements is due to the presence of unpaired electrons in the outermost 3d or 4f orbitals, respectively [21]. Actually, these unpaired electrons possess magnetic moments and contribute to the room-temperature ferromagnetism, although the nature of the magnetic moments of transition metals and rare earth elements are quite different.…”

Section: Introductionmentioning

confidence: 99%

Facile Chemical Synthesis of Doped ZnO Nanocrystals Exploiting Oleic Acid

et al. 2020

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Zinc oxide nanocrystals (ZnO-NCs) doped with transition metal elements or rare earth elements can be probed for magnetic resonance imaging to be used as a molecular imaging technique for accurate diagnosis of various diseases. Herein, we use Mn as a candidate of transition metal elements and Gd as a presenter of rare earth elements. We report an easy and fast coprecipitation method exploiting oleic acid to synthesize spherical-shaped, small-sized doped ZnO-NCs. We show the improved colloidal stability of oleate-stabilized doped ZnO-NCs compared to the doped ZnO-NCs synthesized by conventional sol–gel synthesis method, i.e., without a stabilizing agent, especially for the Mn dopant. We also analyze their structural, morphological, optical, and magnetic properties. We are able to characterize the persistence of the crystalline properties (wurtzite structure) of ZnO in the doped structure and exclude the formation of undesired oxides by doping elements. Importantly, we determine the room-temperature ferromagnetism of the doped ZnO-NCs. This oleate-stabilized coprecipitation method can be subjected as a standard procedure to synthesize doped and also co-doped ZnO-NCs with any transition metal elements or rare earth elements. In the future, oleate-stabilized Gd/Mn-doped ZnO-NCs can be exploited as magnetic resonance imaging (MRI) contrast agents and possibly increase the signal intensity on T1-weighted images or reduce the signal intensity on T2-weighted images.

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Section: Introductionmentioning

confidence: 99%

Facile Chemical Synthesis of Doped ZnO Nanocrystals Exploiting Oleic Acid

et al. 2020

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“…There has been a growing interest in the magnetic properties of vanadium doped oxide systems (2, because of these properties. However, similar to other DMS systems (53), fabrication of ferromagnetic samples has been inconsistent. A number of researchers have reported room temperature ferromagnetism in V-doped ZnO (2,54-56,58,60); others have observed only low temperature ferromagnetism (T c < 10 K) (59); Curie-Weiss paramagnetism coexisting with antiferromagnetism (74), or no FM/AFM interactions for low concentration ion-implanted ZnO:V (72).…”

Section: Introductionmentioning

confidence: 96%

“…An incorrect estimation of the defect states with respect to the valence band maximum (VBM) or conduction band (CB) can lead to spurious vacancy formation energies, or incorrect predictions of ferromagnetic ground states (4). One test system for such calculations is vanadium doped ZnO, primarily due to its multivalent nature, and the unlikelihood of forming secondary magnetic phases in experiment (53). There has been a growing interest in the magnetic properties of vanadium doped oxide systems (2, because of these properties.…”

Section: Introductionmentioning

confidence: 99%

Dilute Magnetic Semiconductors: ab initio Studies of V doped ZnO

et al. 2012

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Density functional theory calculations were performed on bulk and V-doped ZnO. Electronic correlations on the O 2p band were introduced using a Hubbard Hamiltonian (DFT + Ud + Up). An excellent agreement was found between the calculated electronic and crystallographic structure and the experimental values for bulk ZnO. The band gap was found to be 3.4 eV, with a lattice parameter error of < 1%. Antiferromagnetic and ferromagnetic ground states were found to coexist in V-doped ZnO, with little site preference, explaining the conflicting reports in experiments.

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“…The magnetically doped zinc oxide holds a great promise for implementations in optoelectronic devices. [1][2][3][4] As a member of a wide bandgap semiconductor family it is characterized by a small lattice constant, a possible large p-d hybridization, a small spin-orbit interaction, and a large exciton oscillator strength. These properties make ZnO based dilute magnetic semiconductors DMSs highly attractive for room temperature applications.…”

Section: Introductionmentioning

confidence: 99%

Fe dopant in ZnO: 2+ vs 3+ valency and ion-carrier s,p-d exchange interaction

Papierska,

Ciechan,

Bogusławski

et al. 2016

Preprint

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Dopants of transition metal ions in II-VI semiconductors exhibit native 2+ valency. Despite this, 3+ or mixed 3+/2+ valency of iron ions in ZnO was reported previously. Several contradictory mechanisms have been put forward for explanation of this fact so far. Here, we analyze Fe valency in ZnO by complementary theoretical and experimental studies. Our calculations within the generalized gradient approximation (GGA+U ) indicate that the Fe ion is a relatively shallow donor. Its stable charge state is Fe 2+ in ideal ZnO, however, the high energy of the (+/0) transition level enhances the compensation of Fe 2+ to Fe 3+ by non-intentional acceptors in real samples. Using several experimental methods like electron paramagnetic resonance, magnetometry, conductivity, excitonic magnetic circular dichroism and magneto-photoluminescence we confirm the 3+ valency of the iron ions in polycrystalline (Zn,Fe)O films with the Fe content attaining 0.2%.We find a predicted increase of n-type conductivity upon the Fe doping with the Fe donor ionization energy of 0.25 ± 0.02 eV consistent with the results of theoretical considerations. Moreover, our magnetooptical measurements confirm the calculated non-vanishing s,p-d exchange interaction between band carriers and localized magnetic moments of the Fe 3+ ions in the ZnO, being so far an unsettled issue.

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Dilute Magnetic Oxides and Nitrides

Cited by 7 publications

References 82 publications

Facile Chemical Synthesis of Doped ZnO Nanocrystals Exploiting Oleic Acid

Facile Chemical Synthesis of Doped ZnO Nanocrystals Exploiting Oleic Acid

Dilute Magnetic Semiconductors: ab initio Studies of V doped ZnO

Fe dopant in ZnO: 2+ vs 3+ valency and ion-carrier s,p-d exchange interaction

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