共查询到20条相似文献,搜索用时 31 毫秒
1.
Vinit SharmaPriyanka Manchanda Pankaj K. SahotaRalph Skomski Arti Kashyap 《Journal of magnetism and magnetic materials》2012,324(5):786-791
Density-functional calculations are used to determine the electronic structure and magnetic properties of dilute magnetic semiconductors with the composition X1−xMnxN (X=Al, Ga, In, x=6.25% and 12.5%). Emphasis is on the interatomic exchange as a function of the Mn-Mn distance. Our superlattice calculations show that the Mn dopants are spin-polarized with a half-metallic band gap and a magnetic moment of 4 μB per Mn atom at x=6.25 and 12.5%. The Mn (3d) bands lie in the band gap but partially hybridize with valence band or N 2p electrons, depending on the group-III element and on the spin direction. To calculate the exchange interaction parameters Jij, we have used a Green-function approach. The interaction between Mn atoms extends over several interatomic interactions and is mediated by nitrogen (2p) electrons. The exchange is always ferromagnetic and largest for the first nearest neighbors, but substantial ferromagnetic interactions persist over Mn-Mn distances up to sixth nearest neighbors in the considered supercell. 相似文献
2.
A.Z. AlZahrani 《Physica B: Condensed Matter》2012,407(6):992-1002
Within the framework of spin-polarized generalized gradient approximation (σGGA) of the density functional theory (DFT) and pseudopotential method, the structural, magnetic, and electronic properties of graphene and graphane upon the adsorption of manganese atoms have been theoretically investigated. In contrast to the recent results (New J. Phys. 12, 063020 (2010)), Mn atom has been found to be adsorbed on a hollow-site configuration and no appreciable indication to substitute one of the C atoms of the graphene sheet. Unlike the recent results on Mn-doped graphane (Carbon 48, 3901 (2010)), the Mn adatom prefers to adsorb on the top of a carbon atom, forming a bridge with the uppermost hydrogen atoms. The magnetic moment of the Mn-doped graphene is found to be larger than that of the Mn-doped graphane. The structural parameters and electronic properties of both Mn-doped graphene and Mn-doped graphane are determined and compared with the available data. 相似文献
3.
U.P. Verma Sonu Sharma Nisha Devi P. Rajaram 《Journal of magnetism and magnetic materials》2012,324(19):3017-3023
We have investigated the structural, electronic, magnetic and optical properties of Hg1?xMnxTe in the zinc-blende phase for 0≤x≤1. The calculations were performed by using the full potential linearized augmented plane wave plus local orbitals method within the framework of the density functional theory. The lattice constants of Hg1?xMnxTe at different Mn concentrations exhibit Vegard's law perfectly. For spin-up channel the Mn 3d bands are occupied and mixed with the Te 5p bands whereas for spin-down channel the Mn 3d bands are unoccupied. The values of the p–d exchange splitting energy, ?x(pd) as produced by the Mn 3d states are given. The contribution of the valence band and the conduction band in the process of exchange and splitting is described by the exchange coupling constants N0α and N0β. Due to p–d hybridization the magnetic moment of the Mn atom reduces, which results in small local magnetic moments on the non-magnetic Hg and Te sites. The potential applications of Hg1?xMnxTe in infrared device have been discussed on the basis of its optical properties. 相似文献
4.
(Ga1−xMnx)N/GaN digital ferromagnetic heterostructures (DFHs) and (Ga1−xMnx)N/GaN grown on GaN buffer layers by using molecular beam epitaxy have been investigated. The photoluminescence (PL) spectra showed band-edge exciton transitions. They also showed peaks corresponding to the neutral donor-bound exciton and the exciton transitions between the conduction band and the Mn acceptor, indicative of the Mn atoms acting as substitution. The magnetization curves as functions of the magnetic field at 5 K indicated that the saturation magnetic moment in the (Ga1−xMnx)N/GaN DFHs decreased with increasing Mn mole fraction and that the saturation magnetic moment and the coercive field in the (Ga1−xMnx)N/GaN DFHs were much larger than those in (Ga1−xMnx)N thin films. These results indicate that the (Ga1−xMnx)N/GaN DFHs hold promise for potential applications in spintronic devices. 相似文献
5.
Li Chen Yu OuyangHongzhe Pan Yuanyuan SunDaoyong Li 《Journal of magnetism and magnetic materials》2011,323(5):547-551
Using first-principles calculations, we investigate magnetic properties and electronic structures of graphene with H, N and P adsorptions. With a change in adsorption density from 1/50 to 1/162 a band gap changing from ∼1.2 to 0.1 eV emerges in a H-absorbed graphene, leading to the semiconducting graphene and showing ferromagnetism with the magnetic moment of the system changing from 0.76 to 0.42μB. The unpaired electrons in the absorbed N/P atoms are polarized and thus it exhibits magnetic moment per N/P atom changing from 0.38/0.20 to 0.60/0.14μB and metallic and half-metallic magnetism, respectively. The spin-polarized graphene system has a great application prospect in spintronics. 相似文献
6.
《Current Applied Physics》2019,19(12):1391-1398
The structural, magnetic, dielectric and optical properties of Aurivillius Bi6Fe2Ti3O18-based ceramics were investigated in detail. The replacement of Co for Fe/Ti ions obviously varies the grain morphology. Compared with Bi6Fe2Ti3O18 (BFTO) with antiferromagnetic ordering, a spin glass state can be observed in Bi5.25La0.75Fe2Ti3O18 ceramic, while other samples exhibit the ferromagnetic behavior. The specimen Bi6Fe2Ti2(NbCo)0.5O18 (BFTNCO) represents the largest remanent magnetization Mr of 0.93emu/g among all the samples, which can be attributed to the combination of a short lattice parameter c and a large lattice distortion as well as more magnetic ions in a unit cell. The room-temperature dc conductivity of BFTNCO is one order magnitude lower than that of BFTO. In addition, the band gaps of Co-doped samples are about 0.2eV smaller than these of Co-free samples. This work provides a promising path forward to tailor the multiferroic and optical properties in five-layered Aurivillius compounds. 相似文献
7.
The magnetic and crystallographic nature of the compounds CoMn1?xTixSi (0?x?0.5) is studied by X-ray, neutron diffraction and magnetometric measurements. It is shown that the solid solutions arise for 0?x?0.5, with the crystal structure of the NiTiSi type. All compounds are antiferromagnets. The magnetic moment localized on Mn and Co atoms forms a double spiral in both sites. The dilution of the Mn sublattice by Ti atoms change only slightly the magnetic properties - Néel temperature and parameters of magnetic structure. 相似文献
8.
Chen Huang Lihong Han Liyuan Wu Rui Su Jun Chen Pengfei Lu 《The European Physical Journal B - Condensed Matter and Complex Systems》2015,88(6):147
The electronic structure and optical properties of boron-doped, sulfur-doped, andboron-sulfur-codoped graphene systems have been studied by using first-principlescalculations. Energy band structure and density of states are presented to describe theelectronic properties. The doping can open the band gap and change the optical propertiesof graphene. For all optical properties of doped graphene systems, parallel(E ∥) polarization and perpendicular(E ⊥) polarization are presented. Theoptical properties under two kinds of polarizations are reflected in the range of peakheight and the change of some extraordinary features. 相似文献
9.
采用第一性原理平面波超软赝势方法,系统研究了Mn,N共掺杂对锐钛矿相TiO2的晶体结构、缺陷形成能、电子结构、光学性质以及氧化还原能力的影响.研究表明:Mn,N共掺杂锐钛矿相TiO2后,TiO2晶格发生了畸变,导致晶体八面体偶极矩增加,有利于光生电子-空穴对的有效分离;在TiO2带隙中出现了杂质能级,使锐钛矿相TiO2的光学吸收带边红移,可见光区的吸收系数明显增大,有利于光催化效率的提高;在不考虑
关键词:
2')" href="#">锐钛矿相TiO2
第一性原理
Mn和N共掺杂
光催化性能 相似文献
10.
《Chinese Journal of Physics (Taipei)》2018,56(4):1756-1763
First-principles full-potential linearized augmented plane-wave method based on density functional theory is used to investigate the structural, electronic and optical properties of the cubic fluoroelpasolites Cs2NaYF6 within the local density approximation (LDA) and generalized gradient approximation (GGA) for potential exchange correlation. The modified Becke–Johnson (mBJ) potential approximation is also used for calculating the electronic and optical properties of the material. We have analyzed the structural parameters, total and partial densities of states, dielectric functions, absorption and reflectivity. The results show that the band structure of the fluoroelpasolites Cs2NaYF6 has an insulating behavior for the two directions of spin and as a result there is no net magnetic moment. A wide band gap of 9.6 eV is obtained with mBJ-GGA, which allows the application of this material as X-ray storage phosphor materials and scintillators. 相似文献
11.
Electronic structure calculations based on density functional (DFT) theory within the generalized gradient approximation (GGA) for the Ti2CoGa Heusler compound have been performed using the self-consistent full-potential linearized augmented plane wave (FPLAPW) method. The electronic band structures and density of states of the Ti2CoGa compound show that the spin-up electrons are metallic, but the spin-down bands have a gap of 0.5 eV, resulting in stable half-metallic ferrimagnetic behavior with a magnetic moment of 2μB. 相似文献
12.
U.P. Verma Sonu SharmaNisha Devi P.S. BishtP. Rajaram 《Journal of magnetism and magnetic materials》2011,323(5):394-399
We have investigated the structural, electronic and magnetic properties of the diluted magnetic semiconductor (DMS) Cd1−xMnxTe (for x=0.75 and 1.0) in the zinc blende (B3) phase by employing the ab-initio method. Calculations were performed by using the full potential linearized augmented plane wave plus local orbitals (FP-L/APW+lo) method within the frame work of spin-polarized density functional theory (SP-DFT). The electronic exchange-correlation energy is described by generalized gradient approximation (GGA). We have calculated the lattice parameters, bulk modulii and the first pressure derivatives of the bulk modulii, spin-polarized band structures, and total and local densities of states. We estimated the spin-exchange splitting energies Δx(d) and Δx(pd) produced by the Mn3d states, and we found that the effective potential for the minority spin is more attractive than that of the majority spin. We determine the s-d exchange constant N0α (conduction band) and p-d exchange constant N0β (valence band) and these somewhat agree with a typical magneto-optical experiment. The value of calculated magnetic moment per Mn impurity atom is found to be 4.08 μB for Cd0.25Mn0.75Te and 4.09 μB for Cd0.0Mn1.0Te. Moreover, we found that p-d hybridization reduces the local magnetic moment of Mn from its free space charge value of 5.0 μB and produces small local magnetic moments on the nonmagnetic Cd and Te sites. 相似文献
13.
Hailin LiuZhihong Lu ling YueJing Liu Zhanghua GanChang Shu Ting ZhangJing Shi Rui Xiong 《Applied Surface Science》2011,257(22):9355-9361
A series of Ti1−xMoxO2−yNy samples were prepared by using sol-gel method and characterized by X-ray diffraction, transmission electron microscopy and UV-vis absorption spectroscopy. All Ti1−xMoxO2−yNy samples are anatase phase. It is found that Mo, N mono-doping can increase visible light absorption, while (Mo + N) co-doping can greatly enhance absorption in whole visible region. Results of our first-principles band structure calculations reveal that (Mo + N)-doping, especially passivated co-doping can increase the up-limit of dopant concentration and create more impurity bands in the band gap of TiO2, which leads to a greatly increase of its visible-light absorption without a decrease of its redox potential. It reveals that (Mo + N) co-doped TiO2 is promising for a photocatalyst with high photocalystic activity under visible light. 相似文献
14.
《Current Applied Physics》2014,14(7):909-915
In this work, a comparison of magnetic and microwave properties between Mn–Sn–Ti substituted SrM ferrite and nanocomposite of Mn–Sn–Ti substituted SrM ferrite–20% volume multi-walled carbon nanotube (MWCNT) has been done. Phase characterization and crystal structure of the synthesized nanoparticles were tested by X-ray diffraction (XRD). Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectrometry (FTIR) analysis approved that the SrFe12−x(MnSn0.5Ti0.5)x/2O19 nanoparticles were attached on the external surfaces of the MWCNTs. Mӧssbauer spectroscopy (MS) showed the occupancy by non-magnetic Mn2+–Sn4+–Ti4+ cations into the hexagonal lattice structure. Magnetic properties were evaluated by a vibrating sample magnetometer (VSM). The results also indicated that saturation magnetization and coercivity were decreased with an increase in x content and also MWCNTs addition. Microwave absorption properties were investigated by a vector network analyzer (VNA). It was found that with an addition of 20 volume percentage of MWCNTs, the saturation magnetization coupled with coercivity decrease, but reflection loss (RL) increase broadly. Also it proved that with an increase in the thickness of absorption the frequency band shifts from Ku (12–18 GHz) to X (8–12 GHz) band. 相似文献
15.
In this work, we aimed to examine the spin-polarized electronic band structures, the local densities of states as well as the magnetism of ZnMnTe- and CdMnTe-diluted magnetic semiconductors (DMSs) in the ferromagnetic phase, and with 25% of Mn. The calculations are performed by the recent ab initio full potential augmented plane waves plus local orbitals (FP−L/APW+lo) method within the spin-polarized density-functional theory and the local spin density approximation. We have determined the exchange splittings produced by the Mn d states: Δx(d) and Δx(pd), and we found that the effective potential for the minority spin is more attractive than that for the majority spin. Also, we show the nature of the bonding from the charge spin-densities calculations, and we calculate the exchange constants N0α and N0β, which mimics a typical magneto-optical experiment. The calculated total magnetic moment is found to be equal to 5μB for both DMSs. This value indicates that every Mn impurity adds no hole carriers to the perfect ZnTe and CdTe crystals. Furthermore, we found that p–d hybridization reduces the local magnetic moment of Mn and produces small local magnetic moments on the nonmagnetic Te, Zn and Cd sites. 相似文献
16.
Electron beam evaporation technique was used to prepare TiO2 and Ti2O3 thin films onto glass substrates of thicknesses 50, 500 and 1000 nm for each sample. The structural investigations revealed that the as-deposited films are amorphous in nature. Transmittance measurements in the wavelength range (350-2000 nm) were used to calculate the refractive index n and the absorption index k using Swanepoel's method. The optical constants such as optical band gap , optical conductivity σopt, complex dielectric constant, relaxation time τ and dissipation factor tan δ were determined. The analysis of the optical absorption data revealed that the optical band gap Eg was indirect transitions. The optical dispersion parameters Eo and Ed were determined according to Wemple and Didomenico method. 相似文献
17.
Kongping WuShulin Gu Kun TangJiandong Ye Shunming ZhuMengran Zhou Yourui HuangMingxiang Xu Rong ZhangYoudou Zheng 《Journal of magnetism and magnetic materials》2012,324(8):1649-1654
The influences of Mn doping on the structural quality of the ZnxMn1−xO:N alloy films have been investigated by XRD. Chemical compositions of the samples (Zn and Mn content) and their valence states were determined by X-ray photoelectron spectrometry (XPS). Hall effect measurements versus temperature for ZnxMn1−xO:N samples have been designed and studied in detail. The ferromagnetic transitions happened at different TC should explain that the magnetic transition in field-cooled magnetization of Zn1−xMnxO:N films at low temperature is caused by the strong p-d exchange interactions besides magnetic transition at 46 K resulting from Mn oxide, and that the room temperature ferromagnetic signatures are attributed to the uncompensated spins at the surface of anti-ferromagnetic nano-crystal of Mn-related Zn(Mn)O. 相似文献
18.
R. Sobczak 《Solid State Communications》1979,29(5):451-453
Magnetic measurements (temperature and field dependence) on Heusler alloys Ni2(Ti, Mn)Sn and Co2(Ti, Mn)Sn were performed in the ferro- and para-magnetic region. In both systems the composition range was from x = 0 to x = 1. All the Co2(Ti, Mn)Sn samples are ferromagnetic; in the system Ni2Ti1?xMnxSn for x ? 0.2. Our interpretation of the magnetic data differs from that of previous authors. 相似文献
19.
Yao LuPei-Ji Wang Chang-Wen ZhangXian-Yang Feng Lei JiangGuo-Lian Zhang 《Physica B: Condensed Matter》2011,406(17):3137-3141
Using the full-potential linearized augmented plane wave method (FP-LAPW), we have investigated the electronic and optical properties of Sn1−xMnxO2 (x=0, 0.0625, 0.125, 0.1875, 0.25). The doped Mn results in reduction of the band gap, which can be attributed to a series of impurity bands at the bottom of the conduction band caused by the strong hybridization between Mn 3d and O 2p. The results also show that the Mn-doped systems tend to convert into p-type semiconductor with direct band gaps. With the increase of Mn concentration, both the imaginary part of dielectric function and the absorption spectrum show red-shift corresponding to the change of band gaps. 相似文献