The making of ferromagnetic Fe doped ZnO nanoclusters

Ganguli, Nirmal; Dasgupta, Indra; Sanyal, Biplab

doi:10.1063/1.3136904

Cited by 47 publications

(31 citation statements)

References 18 publications

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“…The other possibility is surface-vacancy-induced ferromagnetism. 18 18,39 This will occur mostly in the surface region of the nanoparticles, where the probability of the creation of vacancies is higher. 18 Based on the earlier theoretical study 40 and XAS measurements 41 of nanoparticles, we suggest that the presence of the Fe 3+ ͑O h ͒ ions is due to excess oxygen at the surface of the nanoparticles.…”

Section: Resultsmentioning

confidence: 99%

Electronic structure and magnetism of the diluted magnetic semiconductor Fe-doped ZnO nanoparticles

Kataoka

Kobayashi

Sakamoto

et al. 2010

Journal of Applied Physics

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Articles you may be interested inEvidence of a cluster glass-like behavior in Fe-doped ZnO nanoparticles J. Appl. Phys. 115, 17E123 (2014) We have studied the electronic structure of Fe-doped ZnO nanoparticles, which have been reported to show ferromagnetism at room temperature, by x-ray photoemission spectroscopy, resonant photoemission spectroscopy, x-ray absorption spectroscopy, and x-ray magnetic circular dichroism ͑XMCD͒. From the experimental and cluster-model calculation results, we find that Fe atoms are predominantly in the Fe 3+ ionic state with mixture of a small amount of Fe 2+ and that Fe 3+ ions are dominant in the surface region of the nanoparticles. It is shown that the room temperature ferromagnetism in the Fe-doped ZnO nanoparticles primarily originated from the antiferromagnetic coupling between unequal amounts of Fe 3+ ions occupying two sets of nonequivalent positions in the region of the XMCD probing depth of ϳ2 -3 nm.

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Section: Resultsmentioning

confidence: 99%

Electronic structure and magnetism of the diluted magnetic semiconductor Fe-doped ZnO nanoparticles

Kataoka

Kobayashi

Sakamoto

et al. 2010

Journal of Applied Physics

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“…Thus hopping induced interaction between the dopant Mn atoms stabilizes the tendency of FM for this system, similar to our previous observation for Fe doped ZnO cluster with the same defect state. 12 In this context, an experimental report has also pointed out that deficiency of electrons can induce FM in Mn doped ZnO quantum dots. 3 A calculation by Feng et al in the framework of TDDFT also claims that double exchange mechanism induced by optical excitation can stabilize FM in Mn doped ZnO quantum dots.…”

Section: B Effect Of Vacancymentioning

confidence: 99%

“…In a recent work, using GGA+ U on Fe doped ZnO clusters we have shown that defects under suitable conditions can induce ferromagnetic interactions between the dopant Fe atoms, whereas AFM coupling dominates in a neutral defect-free cluster. 12 In addition, there are several calculations that suggest that ZnO nanocluster may be ferromagnetic without TM dopants. Schoenhalz et al 13 have proposed that the surface states promoted by extended defects ͑e.g., grain boundaries͒ may play an important role in mediating ferromagnetic interaction in such materials.…”

Section: Introductionmentioning

confidence: 99%

“…It was also reported that doping of Mn into the Zn 12 O 12 cluster yields antiferromagnetic ͑AFM͒ ground state for small Mn-Mn distance while ferromagnetic and AFM states are degenerate for large Mn-Mn distance. 8 Very recently, the structural and magnetic properties of several 3d TM doped Zn 12 O 12 clusters were investigated in the framework of GGA. 9 The authors find that most of the TM dopants stabilize either in paramagnetic or in AFM state, except Co and Ni, where the ferromagnetic and AFM states are found to be energetically very close.…”

Section: Introductionmentioning

confidence: 99%

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Electronic structure and magnetism of transition metal doped Zn12O12 clusters: Role of defects

Ganguli

Dasgupta

Sanyal

2010

Journal of Applied Physics

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Impacts of enhanced electronic correlation in anion p-orbitals on electronic structure and magnetic properties of nitrogen or carbon doped zinc oxide J. Appl. Phys. 111, 07E313 (2012) Magneto-optical spectrum of ZnO nanorods J. Appl. Phys. 111, 044305 (2012) First-principles study on electronic structures and magnetic properties of AlN nanosheets and nanoribbons J. Appl. Phys. 111, 043702 (2012) p-f hybridization in the ferromagnetic semiconductor HoN Appl. Phys. Lett. 100, 072108 (2012) Visible light photocatalysis of single-walled (Zn4/6Cu2/6O)3/(Zn5/6Cu1/6O)3 superlattice nanotube for redox reaction of water calculated by generalized gradient approximations with the Hubbard U model J. Appl. Phys. 111, 034318 (2012) Additional information on J. Appl. Phys. We present a comprehensive study of the energetics and magnetic properties of ZnO clusters doped with 3d transition metals ͑TMs͒ using ab initio density functional calculations in the framework of generalized gradient approximation+ Hubbard U ͑GGA+ U͒ method. Our results within GGA+ U for all 3d dopants except Ti indicate that antiferromagnetic interaction dominates in a neutral, defect-free cluster. Formation energies are calculated to identify the stable defects in the ZnO cluster. We have analyzed in details the role of these defects to stabilize ferromagnetism when the cluster is doped with Mn, Fe, and Co. Our calculations reveal that in the presence of charged defects the TM atoms residing at the surface of the cluster may have an unusual oxidation state, that plays an important role to render the cluster ferromagnetic. Defect induced magnetism in ZnO clusters without any TM dopants is also analyzed. These results on ZnO clusters may have significant contributions in the nanoengineering of defects to achieve desired ferromagnetic properties for spintronic applications.

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“…Current interest in such magnetic nano-particle systems is motivated by unique electronic structures and magnetism at the surfaces of the nano-particles which are different from the inner core region. In the nano-particle form, the structural and electronic properties are modified by surface defects such as Zn and O vacancies with broken chemical bonds and charge imbalance, which may mediate or modify exchange coupling between the doped atoms [7]. For example, high-valence (3+ and 4+) Mn and Co ions are found to be present in the surface of paramagnetic (Mn,Co)-codoped ZnO nano-particles [8], probably due to the formation of Zn vacancies (V Zn ) in the surface region.…”

Section: Introductionmentioning

confidence: 99%

X-Ray Absorption Spectroscopy and X-Ray Magnetic Circular Dichroism Studies of Transition-Metal-Codoped ZnO Nano-Particles

Kataoka

Yamazaki

Singh

et al. 2012

e-J. Surf. Sci. Nanotechnol.

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We report on x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) studies of the paramagnetic (Mn,Co)-codoped ZnO [ZnO:(Mn,Co)] and ferromagnetic (Fe,Co)-codoped ZnO[ZnO:(Fe,Co)] nano-particles. Both the surface-sensitive total-electron-yield mode and the bulk-sensitive total-fluorescence-yield mode have been employed to extract the valence and spin states of the surface and inner core regions of the nano-particles. In the case of paramagnetic ZnO:(Mn,Co) nano-particles, the doped Mn and Co atoms are in a mixed-valence (2+, 3+, and 4+) state and the relative concentrations of the high-valence (3+ and 4+) Mn and Co ions are higher in the surface region than in the inner core region. In the case of the ferromagnetic ZnO:(Fe,Co) nano-particles, the doped Fe and Co atoms are found to be in a mixed-valence (2+ and 3+) state and the relative concentrations of the Fe 3+ and Co 3+ ions are higher in the surface region than in the inner core region. The XMCD spectra show that the Fe 3+ ions in the surface region mainly give rise to the ferromagnetism while the doped Co ions in the surface region show only paramagnetic behaviors. The transition-metal atoms in the inner core region do not show magnetic signals, meaning that they are nonmagnetic states due to antiferromagnetic coupling. The present result combined with the previous results on transition-metal-doped ZnO nano-particles suggest that doped holes, probably due to Zn vacancy formation at the surfaces of the nano-particles, rather than doped electrons are involved in the occurrence of ferromagnetism in these systems.

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The making of ferromagnetic Fe doped ZnO nanoclusters

Cited by 47 publications

References 18 publications

Electronic structure and magnetism of the diluted magnetic semiconductor Fe-doped ZnO nanoparticles

Electronic structure and magnetism of the diluted magnetic semiconductor Fe-doped ZnO nanoparticles

Electronic structure and magnetism of transition metal doped Zn12O12 clusters: Role of defects

X-Ray Absorption Spectroscopy and X-Ray Magnetic Circular Dichroism Studies of Transition-Metal-Codoped ZnO Nano-Particles

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