Density functional study of magnetic properties in Zn-doped SnO2 (original) (raw)
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Density functional study of magnetic properties in Zn-doped SnO[sub 2]
Journal of Applied Physics, 2010
ABSTRACT Magnetic properties in Zn-doped SnO2 are examined through the first-principles electronic structure calculations based on density functional theory. Our results reveal that Zn-doping induces localized spin magnetic moments primarily on the first coordination shell of O atoms surrounding the Zn atom as well on Zn atom with total magnetic moment of 1.47 μB per supercell. Holes localized on O atoms in ZnO6 are polarized with the same spin orientation as that of the dopant. Ferromagnetic coupling between Zn ions in Zn-doped SnO2 is attributed to the hole-mediated p-d exchange coupling interaction. With respect to native defects in Zinc-doped SnO2, formation of oxygen vacancy (VO) is suppressed whereas formation of tin vacancy (VSn) is facilitated due to Zn-doping. It is found that the observed ferromagnetism in Zn-doped SnO2 mainly originates from the Zn dopant rather than exclusively the formation of VSn.
Vacancy-induced magnetism in SnO2: A density functional study
We study the magnetic and electronic properties of defects in SnO2 using pseudopotential and all electron methods. Our calculations show that bulk SnO2 is non-magnetic, but it shows magnetism with a magnetic moment around 4.00 µB due to Sn vacancy (VSn). The magnetic moment comes mainly from O atoms surrounding VSn and Sn atoms, which couple antiferromagnetically with the O atoms in the presence of VSn. The coupling between different Sn vacancies is also studied and we find that these defects not only couple ferromagnetically but also antiferromagnetically and ferrimagnetically. Our calculations demonstrate that the experimentally observed giant magnetic moment of transition metal doped SnO2 can be attributed to VSn. PACS numbers: 75.50.Pp, 61.72.Ji, 71.22.+i In many diluted magnetic semiconductor (DMS) the non-magnetic matrix is a conventional compound semiconductor such as GaAs 1 or InAs 2 . These DMSs have low solubility limit and their Curie temperatures (T C )s are well below room temperature (RT), which disqualify them for spintronic devices. In other classes of DMS the transition metal (TM) is embedded in oxide semiconductors, which are conventionally known as oxide-DMS (ODMS), such as ZnO with Co or Mn doping 3,4,5 , TiO 2 (anatase) with Co 6 and SnO 2 with Co 7 . These ODMSs have large magnetic moments and their T C s are well above RT. Therefore these are good candidates for spintronic devices.
The Journal of Physical Chemistry C, 2015
We present here an ab initio study of the structural, magnetic, and hyperfine properties of Fe-doped rutile SnO 2 for different concentrations and distributions of the Fe atoms and oxygen vacancies in the SnO 2 host. The calculated results are compared with experimental ones obtained by Mossbauer spectroscopy and X-ray absorption techniques. This comparison enables us to characterize the local structure around Fe atoms and to identify the different hyperfine interactions that are observed in samples prepared by different methods. It is concluded that oxygen vacancies are fundamental for the ferromagnetic response of Fe-doped SnO 2. The ab initio calculations show that two Fe ions sharing an oxygen vacancy are coupled ferromagnetically, forming a bound magnetic polaron (BMP), and that two neighbor BMPs are aligned antiparallel to each other. Electron doping plays a fundamental role mediating the magnetic coupling between the BMP inducing ferromagnetic alignment between the BMPs.
Electronic structure and spontaneous magnetization in Mn-doped SnO2
Journal of Applied Physics, 2020
Mn-doped SnO 2 is a promising dilute magnetic semiconductor; however, there are many inconsistent reports on the magnetic ordering in the literature. We investigate the magnetic ordering and the local electronic structure in stoichiometric and Mn-doped (with Mn concentrations of 1 at.%, 3 at.%, and 6 at.%) SnO 2 using magnetization measurements, Mn L 2,3-edge and O K-edge x-ray absorption fine structure measurements, and density functional theory and model Hamiltonian calculations. We find that paramagnetic and ferromagnetic behavior is present as a function of Mn concentration and, in particular, that paramagnetic, ferromagnetic, and antiferromagnetic order coexist independently in Mn(6%):SnO 2. Simultaneously, we find that Mn 2þ , Mn 3þ , and Mn 4þ also coexist in Mn(6%):SnO 2. These findings demonstrate the care needed to study Mn:SnO 2 and point to the wealth of magnetic behaviors that might be realized with careful control of synthesis conditions.
Magnetism of Zn-doped SnO2: Role of surfaces
Journal of Applied Physics, 2014
Surface effects on the magnetization of Zn-doped SnO 2 are investigated using first principles method. Magnetic behavior of Zn-doped bulk and highest and lowest energy surfaces-(001) and , respectively, are investigated in presence and absence of other intrinsic defects. The Zn-doped and surfaces of SnO 2 show appreciable increase in the magnetic moment (MM) compared to Zn-doped bulk SnO 2 . Formation energies of Zn defects on both the surfaces are found to be lower than those in bulk SnO 2 . 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. V C 2014 AIP Publishing LLC.
First-principle study of magnetism in Co-doped SnO2
Journal of magnetism and …, 2009
The effects of Co dopants and oxygen vacancies on the electronic structure and magnetic properties of the Co-doped SnO 2 are studied by the first-principle calculations in full-potential linearized augmented plane wave formalism within generalized gradient approximations. The Co atoms favorably substitute on neighboring sites of the metal sublattice. Without oxygen vacancies, the Co atoms are at low spin state independent of concentration and distribution of Co atoms, and only the magnetic coupling between nearest-neighbor Co atoms is ferromagnetic through direct exchange and super-exchange interaction. Oxygen vacancies tend to locate near the Co atoms. Their presence strongly increases the local magnetic moments of Co atoms, which depend sensitively on the concentration and distribution of Co atoms. Moreover, oxygen vacancies can induce the long-range ferromagnetic coupling between wellseparated Co atoms through the spin-split impurity band exchange mechanism. Thus the room temperature ferromagnetism observed experimentally in the Co-doped SnO 2 may originate from the combination of short-range direct exchange and super-exchange interaction and the long-range spin-split impurity band exchange model.
Journal of Physics and Chemistry of Solids, 2018
A density functional theory (DFT) employing generalized gradient approximation (GGA) has been used to study the electronic and magnetic properties of Mo doped SnO2. The presence of symmetric density of states (DOS) and direct band gap in Sn1−xMoxO2 (at x=0.00) predicts this material to be a direct band gap semiconductor. The substitution of Mo atoms on the Sn sites induced a spin functionality on the DOS. The Mo impurities played an important role in facilitating the hybridization between Mod and O-p orbitals. The p − d hybridization gives an antisymmetric DOS at the EF by creating an exchange splitting at Mod states. The higher value of energy exchange splitting is responsible for the of partial magnetic moment at Mo site. In all composition except at x=0.0, the a wide band gaps are preserved at the spin down region and a metallic characteristic at the spin up region, confirm it's metal-semiconductor hybrid property. These type of materials exhibit 100% spin polarization at the EF , which can be a potential candidate for electron-spin based futuristic devices.
The structural and electronic properties of S-doped ZnO are investigated by density functional theory (DFT) and empirical pseudopotential method (EPM). Using the Heyd–Scuseria–Ernzerhof (HSE) hybrid functional with an adjusted mixing coefficient a , we obtain a good agreement on lattice parameters and band gap energy with the available experimental data. We have also investigate the Zn-vacancy effects on the electronic and magnetic properties of S-doped ZnO. Our calculations demonstrate that S impurity prefers to be close to the cation vacancy in the apical position. The magnetic analysis with the HSE functional shows a triplet state character with a total magnetic moment of 1.81 l B , which is mainly arises from the p -orbitals of the atoms around the Zn-vacancy (15% from S, 12% from Zn and 73% from O-atoms). The substitution of S by an isovalent atom decreases the total magnetic moments of the system and weakens the local triplet state without destroying it.
Origin of magnetic frustration in Bi3Mn4O12(NO3)
Physical Review B
Bi 3 Mn 4 O 12 (NO 3) (BMNO) is a honeycomb bilayers antiferromagnet, not showing any ordering down to very low temperatures despite having a relatively large Curie-Weiss temperature. Using ab initio density functional theory, we extract an effective spin Hamiltonian for this compound. The proposed spin Hamiltonian consists of antiferrimagnetic Heisenberg terms with coupling constants ranging up to third intralayer and fourth interlayer neighbors. Performing Monte Carlo simulation, we obtain the temperature dependence of magnetic susceptibility and so the Curie-Weiss temperature and find the coupling constants which best match with the experimental value. We discover that depending on the strength of the interlayer exchange couplings, two collinear spin configurations compete with each other in this system. Both states have in plane Néel character, however, at small interlayer coupling spin directions in the two layers are antiparallel (N 1 state) and discontinuously transform to parallel (N 2 state) by enlarging the interlayer couplings at a first order transition point. Classical Monte Carlo simulation and density matrix renormalization group calculations confirm that exchange couplings obtained for BMNO are in such a way that put this material at the phase boundary of a first order phase transition, where the trading between these two collinear spin states prevents it from setting in a magnetically ordered state.
Intrinsic magnetism in nanosheets of SnO2: A first-principles study
Journal of Magnetism and Magnetic Materials, 2013
We propose intrinsic magnetism in nanosheets of SnO2, based on first-principles calculations. The electronic structure and spin density reveal that p orbitals of the oxygen atoms, surrounding Sn vacancies, have a non itinerant nature which gives birth to localized magnetism. A giant decrease in defect formation energies of Sn vacancies in nanosheets is observed. We, therefore, believe that native defects can be stabilized without any chemical doping. Nanosheets of different thicknesses are also studied, and it is found that it is easier to create vacancies, which are magnetic, at the surface of the sheets. SnO2 nanosheets can, therefore, open new opportunities in the field of spintronics.