Surface-induced magnetism in C-doped SnO2

Rahman, Gul; García‐Suárez, Víctor M.

doi:10.1063/1.3302468

Cited by 56 publications

(47 citation statements)

References 27 publications

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“…Neutral and doubly ionized oxygen vacancies on (001) and (110) surfaces are also found to be non-magnetic as in the case of bulk; this is in agreement with previous DFT-GGA results. 23 However, singly ionized oxygen vacancies are found to be magnetic on (001) surface and nonmagnetic (110) surface.…”

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confidence: 99%

“…It has also been found that even nonmagnetic-nonmetallic atoms like C, N, and nonmagnetic, alkali metallic atoms like Mg, K can also induce magnetism in oxides. 23,47 Nanoparticles having radius of only a few nanometers will have a large surface-to-volume ratio. The effect of surfaces in inducing the magnetism in oxide nanoparticles while doped with either magnetic or nonmagnetic atoms has not been investigated in detail.…”

Section: -mentioning

confidence: 99%

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Magnetism of Zn-doped SnO2: Role of surfaces

Pushpa

Ramanujam

2014

Journal of Applied Physics

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Surface effects on the magnetization of Zn-doped SnO2 are investigated using first principles method. Magnetic behavior of Zn-doped bulk and highest and lowest energy surfaces—(001) and (110), respectively, are investigated in presence and absence of other intrinsic defects. The Zn-doped (110) and (001) surfaces of SnO2 show appreciable increase in the magnetic moment (MM) compared to Zn-doped bulk SnO2. Formation energies of Zn defects on both the surfaces are found to be lower than those in bulk SnO2. Zn doping favors the formation of oxygen vacancies. The density of states analysis on the Zn-doped (110) surface reveals that the spin polarization of the host band occurs primarily from p-orbitals of bridging oxygen atoms and the Zn atom itself contributes minimally. The present work provides a key understanding on the role played by the surfaces in inducing the magnetism of doped nanoparticles and thin films.

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confidence: 99%

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confidence: 99%

Magnetism of Zn-doped SnO2: Role of surfaces

Pushpa

Ramanujam

2014

Journal of Applied Physics

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“…[1][2][3] SnO 2 has been extensively researched as a dilute magnetic semiconductor since Dietl 4 predicted room temperature ferromagnetism (RTFM) in Mn-doped ZnO 4 , and several theoretical models propose to explain observations of RTFM in SnO 2 . [5][6][7] Recent computational work predicts RTFM in SnO 2 due to nitrogen substitution 8 , surface carbon 9 , or non-magnetic dopants. 10,11 Raman et al proposed RTFM due to tin vacancies 12 , but V sn is not considered thermodynamically favorable.…”

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confidence: 99%

Size, surface structure, and doping effects on ferromagnetism in SnO2

Alanko

Thurber

Hanna

et al. 2012

Journal of Applied Physics

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The effects of crystallite size, surface structure, and dopants on the magnetic properties of semiconducting oxides are highly controversial. In this work, Fe:SnO 2 nanoparticles were prepared by four wet-chemical methods, with Fe concentration varying from 0-20%. Samples were characterized by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). Analysis confirmed pure single-phase cassiterite with a crystallite size of 2.6 ± 0.1 nm that decreased with increasing Fe%. Fe concentration was confirmed from XPS studies, with Fe ions in the 3+ oxidation state. Pure SnO 2 showed highly reproducible weak magnetization that varied significantly with synthesis method. Interestingly, doping SnO 2 with Fe<2.5% produced enhanced magnetic moments in all syntheses; the maximum of 1.6x10 -4 µ B /Fe ion at 0.1% Fe doping was much larger than the 2.6x10 -6 µ B /Fe ion of pure Fe oxide nanoparticles synthesized under similar conditions. At Fe≥2.5%, the magnetic moment was significantly reduced. This work shows that (i) pure SnO 2 can produce an intrinsic ferromagnetic behavior that varies with differences in surface structure, (ii) very low Fe doping results in high magnetic moments, (iii) higher Fe doping reduces magnetic moment and destroys ferromagnetism, and (iv) there is an interesting correlation between changes in magnetic moment, band gap, and lattice parameters. These results support the possibility that the observed ferromagnetism in SnO 2 might be influenced by modification of the electronic structure by dopant, size, and surface structure. Introduction:

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“…[21][22][23] To go beyond vacancy-induced magnetism, we also proposed possible magnetism induced by light elements, e.g., C, and Li. 24,25 Recent theoretical calculations further show that magnetism can be induced with NM impurities. [2][3][4]26,27 A good example of NM impurity is carbon, which has been shown theoretically and experimentally that C-doped SnO 2 films can exhibit feromagnetic behaviour at room temperature, 24,28 where C does not induce magnetism in bulk SnO 2 , when located at the oxygen site.…”

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confidence: 99%

“…24,25 Recent theoretical calculations further show that magnetism can be induced with NM impurities. [2][3][4]26,27 A good example of NM impurity is carbon, which has been shown theoretically and experimentally that C-doped SnO 2 films can exhibit feromagnetic behaviour at room temperature, 24,28 where C does not induce magnetism in bulk SnO 2 , when located at the oxygen site. 24,28 Now, it is a firm belief that magnetism in NM hosts can be tuned either by vacancies or light elements.…”

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Spin-polarized surface state in Li-doped SnO₂(001)

Din

Rahman

2014

RSC Adv.

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Using LDA+U , we investigate Li-doped rutile SnO2(001) surface. The surface defect formation energy shows that it is easier for Li to be doped at surface Sn site than bulk Sn site in SnO2. Li at surface and sub-surface Sn sites has a magnetic ground state, and the induced magnetic moments are not localized at Li site, but spread over Sn and O sites. The surface electronic structures show that Li at surface Sn site shows 100% spin-polarization (half metallic), whereas Li at sub-surface Sn site does not have half metallic state due to Li-Sn hybridized orbitals. The spin-polarized surface has a ferromagnetic ground state, therefore, ferromagnetism is expected in Li-doped SnO2(001) surface.In the past, decade density functional theory (DFT) has proven to be a predictive tool to discover new materials for certain applications, specially in the area of magnetism. With DFT, many new materials have been discovered and then synthesised.1-5 DFT has also predicted spin polarized materials [6][7][8] . One of the new materials is oxide-based diluted magnetic semiconductor, which has potential applications in spintronics. The main quest in this area is to discover magnetic materials having transition temperature (T c ), which is the temperature at which a system changes from a paramagnetic(disorder phase) to a magnetic phase(order phase), well above room temperature and large magnetization and spin-polarization. With this hope, transition-metals (TMs) were doped into nonmagnetic (NM) semiconductor hosts, 9,10 but later on these TM doped systems were found to have inherent issues, i.e., clustering, antisite defects. 11SnO 2 -based diluted system evoked particular attention when S. B. Ogale et al.12 found a giant magnetic moment (GMM) in Co-doped SnO 2 . Following this discovery, TM doped-SnO 2 has been extensively studied both experimentally and theoretically.13-19 Later on in 2008, our theoretical calculations showed that the Sn vacancies are responsible for magnetism in SnO 2 .20 This opened a new area of magnetism, where magnetism is made possible without doping of magnetic impurities, which are confirmed experimentally. [21][22][23] To go beyond vacancy-induced magnetism, we also proposed possible magnetism induced by light elements, e.g., C, and Li. 24,25Recent theoretical calculations further show that magnetism can be induced with NM impurities.2-4,26,27 A good example of NM impurity is carbon, which has been shown theoretically and experimentally that C-doped SnO 2 films can exhibit feromagnetic behaviour at room temperature, 24,28 where C does not induce magnetism in bulk SnO 2 , when located at the oxygen site.24,28 Now, it is a firm belief that magnetism in NM hosts can be tuned either by vacancies or light elements. In oxides, the magnetic vacancies can be created either at cation site or anion site. Most of the theoretical work show that the cation vacancies are magnetic, 29-32 but there has remained an open question that how to stabilize magnetic vacancies due to their higher formation energies? Very recently, th...

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Surface-induced magnetism in C-doped SnO2

Cited by 56 publications

References 27 publications

Magnetism of Zn-doped SnO2: Role of surfaces

Magnetism of Zn-doped SnO2: Role of surfaces

Size, surface structure, and doping effects on ferromagnetism in SnO2

Spin-polarized surface state in Li-doped SnO₂(001)

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Surface-induced magnetism in C-doped SnO2

Cited by 56 publications

References 27 publications

Magnetism of Zn-doped SnO2: Role of surfaces

Magnetism of Zn-doped SnO2: Role of surfaces

Size, surface structure, and doping effects on ferromagnetism in SnO2

Spin-polarized surface state in Li-doped SnO2(001)

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Spin-polarized surface state in Li-doped SnO₂(001)