Defect induced ferromagnetism in Co-doped ZnO thin films

Fonin, Mikhail; Mayer, G.; Biegger, Erwin; Janssen, Nils; Beyer, Markus; Thomay, Tim; Bratschitsch, Rudolf; Dedkov, Yuriy; Rüdiger, Ulrich

doi:10.1088/1742-6596/100/4/042034

Cited by 21 publications

(12 citation statements)

References 22 publications

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“…In Co-doped ZnO, for example, the role of defects in the observed room-temperature ferromagnetism was studied by several groups [11][12][13]. While Khare et al [12] found Zn interstitials to play a crucial role in mediating ferromagnetism in Co-doped ZnO, Fonin et.…”

Section: Introductionmentioning

confidence: 99%

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Role of oxygen vacancies in room-temperature ferromagnetism in cobalt-substitutedSrTiO3

et al. 2014

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Ferromagnetic insulating behaviour has recently been demonstrated in cobalt-substituted SrTiO 3 at room temperature [1]. Experimentally, it was found that a well-defined hysteresis loop only occurs at high Co concentrations of 30-40%. X-ray photoelectron spectroscopy also indicated that Co substitutes for Ti with Co being in high-spin +2 oxidation state. In this work, we employ density-functional theory to explain the experimentally observed properties of cobalt-substituted SrTiO 3 . We examine in detail the role of oxygen vacancy (OV) defects and their formation of defect complexes with the Co ions as the origin of the ferromagnetic insulating behaviour. Our first-principles thermodynamic calculations indicate that OV defects are much more likely to occur next to Co atoms where their formation energies could be reduced by as much as 1.28 eV compared to that in bulk SrTiO 3 . We also find that Co in these Co-OV complexes occurs in the high-spin state in agreement with core level spectroscopy, and identify a linear arrangement of the Co-OV defect complexes to be the most energetically favourable structure. These defect complexes are also shown to interact ferromagnetically and that their magnetic interaction is found to be short-ranged, consistent with the relatively high Co concentrations needed experimentally for ferromagnetism to be observed in cobalt-substituted SrTiO 3 . I.Introduction The discovery of room-temperature ferromagnetism in doped transition metal oxides by Matsumoto et al. [2] has initiated many theoretical and experimental studies, owing to potential applications of these materials in spintronics. For example, , SnO 2 [5-6], In 2 O 3 [7][8] and TiO 2 [9][10], have all been reported to show room-temperature ferromagnetism when doped with magnetic ions. Increasing the Curie temperature and being able to control the spin degrees of freedom remain major challenges in this field. In this respect, defects in these materials, both intrinsic and extrinsic, play an important role. Defects provide additional carriers to the system (electrons or holes) which could significantly alter magnetic interactions and the Curie temperature in these materials.

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Section: Introductionmentioning

confidence: 99%

“…al. [11] proposed instead that the ferromagnetic properties are strongly correlated with the presence of oxygen vacancies. Liu et al [13], on the other hand, proposed the combination of Al-donor and oxygen vacancy defects to be responsible for a strong carrier mediated ferromagnetic interaction in Co-doped ZnO.…”

Section: Introductionmentioning

confidence: 99%

Role of oxygen vacancies in room-temperature ferromagnetism in cobalt-substitutedSrTiO3

et al. 2014

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“…It is suggested that the V o plays a crucial role in realizing the RTFM. Fonin et al [33] also found that the oxygen vacancies or oxygen related defects, rather than the zinc related defects, constituted the bound magnetic polarons. The Zn(Co,Na)O film showed a high resistance after annealling in Ar and a good p-type behavior when annealed in O 2 , but both of them showed paramagnetism.…”

Section: Resultsmentioning

confidence: 98%

Ferromagnetism induced by donor-related defects in Co-doped ZnO thin films

Zhang

Lü

et al. 2011

Journal of Alloys and Compounds

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“…Many studies described the fabrication techniques of ZnO thin film [4][5][6][7][8][9][10][11]. However, Co doped ZnO thin film has been deposited by Pulsed Laser Deposition (PLD), Molecular Beam Epitaxy and Sputtering methods [12][13][14][15][16][17][18]. Considering the film purity and quality electron beam evaporation has been adopted as a noble and widely used film fabrication technique.…”

Section: Introductionmentioning

confidence: 99%

Technological Regimes Searching the Effect of Thermal Annealing on Optical and Electrical Properties of Co/ZnO Multilayer Thin Film of Different Thickness

Hossain¹

2017

IJHEP

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Abstract:The fabrication of the Co/ZnO multilayer thin film for studying the influence of thermal annealing on optical and electrical properties is presented in this paper. In this case, at first Co/ZnO multilayer films were prepared by e-beam evaporation in a vacuum at a pressure of 3.2×10 -5 torr. In the multilayer, the thickness of Co and ZnO was kept same. Each layer thickness was varied from 5 nm to 15 nm and repeated three times. The deposition rate of the Co and ZnO thin films are about 1.33 nm/s & 1.43 nm/s respectively. The optical and electrical properties of the deposited and annealed Co/ZnO films had been studied. The average transparency of Co/ZnO multilayer thin film is roughly about 55% and decreased with increasing film thickness and increased when annealed. The T. C. R. of deposited and annealed Co/ZnO multilayer thin films in all cases is negative which indicates that the thin films are semiconducting in nature.

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Defect induced ferromagnetism in Co-doped ZnO thin films

Cited by 21 publications

References 22 publications

Role of oxygen vacancies in room-temperature ferromagnetism in cobalt-substitutedSrTiO3

Role of oxygen vacancies in room-temperature ferromagnetism in cobalt-substitutedSrTiO3

Ferromagnetism induced by donor-related defects in Co-doped ZnO thin films

Technological Regimes Searching the Effect of Thermal Annealing on Optical and Electrical Properties of Co/ZnO Multilayer Thin Film of Different Thickness

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