Dilute Magnetic Properties Research Articles

The influence of Mn-doping types on electronic structure and dilute magnetic property of Ca2Ge

The dilute magnetic semiconductor (DMS) materials have important application prospects in the field of electronic science and technology. Ca2Ge is a new environmentally friendly semiconductor material. The structure characteristics indicate that the dilute magnetic properties can be achieved by doping, in the theory. There are CI, CII, CIII, OI, OII and OIII six doped types by Mn doping. For the CI, CII and OIII, Ca2Ge is a semiconductor with a band gap of 0.21 eV, 0.21 eV and 0.065 eV, respectively; For the OII, Ca2Ge turns into a semi-metallic; For the CIII and OI, Ca2Ge turns into a metal. Ca2Ge trans into ferromagnetism with Mn doped, the molecular magnetic moments of CI, CII, CIII, OI, OII and OIII are 5 μB, 5 μB, 1 μB, 5 μB, 5 μB and 7 μB, respectively. The results of the projected density of states (PDOS) indicated that the magnetism mainly comes from the Mn 3d orbital spin, the orbital population shows that the spin of Mn atom affects the spin of Ca atom and the spin of Ge atom, the magnetic moment that is excited by Mn atom doping.

Improving the magnetic moment of Ca2Ge and promoting the conversion of semiconductors to diluted magnetic semiconductors using Mn-doping.

The dilute magnetic properties of materials have important potential applications in the field of electronic science and technology. Intrinsic Ca2Ge is a new environmentally friendly semiconductor material, and exhibits cubic and orthorhombic phases. The crystal structure characteristics of Ca2Ge indicate that the modulation of its dilute magnetic properties can theoretically be achieved by doping with magnetic elements. The study of band structures shows that Ca2Ge is a semiconductor, while Mn doped Ca2Ge is a semi-metal. The results of density of states and atomic population analysis show that Mn doped Ca2Ge exhibits ferrimagnetism with a magnetic moment of 5 μB, and the orbital splitting energy of the Mn atom is 1.0 eV. Mn-doping changes the cubic crystal field of Ca2Ge, and the charge transfer and electron polarization of Ca d and Ge p orbitals are affected by Mn atoms. The Ca d orbital is split into dzz, dzy, dzx, dxx-yy and dxy orbitals, and the contribution of spin of each d split orbital to the magnetic moment of the Ca d orbital is in the order dxy > dyz > dxz > dxx-yy > dzz. The Ge p orbital is split into px, py and pz orbitals, and the spin contribution of each p orbital to the magnetic moment of the Ge p orbital is in the order py > pz > px. The analysis of atom populations shows that the charge transfer and spin of Ca and Ge change with Mn doping, and the difference between spin up and spin down increases, improving the magnetism of Ca2Ge and forming a dilute magnetic semiconductor.

Magnetic Order, Electrical Doping, and Charge-State Coupling at Amphoteric Defect Sites in Mn-Doped 2D Semiconductors.

Two-dimensional (2D) dilute magnetic semiconductors (DMSs) are attractive material platforms for applications in multifunctional nanospintronics due to the prospect of embedding controllable magnetic order within nanoscale semiconductors. Identifying candidate host material and dopant systems requires consideration of doping formation energies, magnetic ordering, and the tendency for dopants to form clustered domains. In this work, we consider the defect thermodynamics and the dilute magnetic properties across charge states of 2D-MoS2 and 2D-WS2 with Mn magnetic dopants as candidate systems for 2D-DMSs. Using hybrid density functional calculations, we study the magnetic and electronic properties of these systems across configurations with thermodynamically favorable defects: 2D-MoS2 doped with Mn atoms at sulfur site (MnS), at two Mo sites (2MnMo), on top of a Mo atom (Mn-top), and at a Mo site (MnMo). While the majority of the Mn-defect complexes provide trap states, MnMo and MnW are amphoteric, although previously predicted to be donor defects. The impact of cluster formation of these amphoteric defects on magnetic ordering is also considered; both MnMo-MnMo (2Mn2Mo) and MnW-MnW (2Mn2W) clusters are found to be stable in ferromagnetic (FM) ordering. Interestingly, we observed the defect charge state dependent magnetic behavior of 2Mn2Mo and 2Mn2W clusters in 2D-TMDs. We investigate that the FM coupling of 2Mn2Mo and 2Mn2W clusters is stable in only a neutral charge state; however, the antiferromagnetic (AFM) coupling is stable in the +1 charge state. 2Mn2Mo clusters provide shallow donor levels in AFM coupling and deep donor levels in FM coupling. 2Mn2W clusters lead to trap states in the FM and AFM coupling. We demonstrate the AFM to FM phase transition at a critical electron density nce = 3.5 × 1013 cm-2 in 2D-MoS2 and 2D-WS2. At a 1.85% concentration of Mn, we calculate the Curie temperature of 580 K in the mean-field approximation.

The structural and dilute magnetic properties of (Co, Li) co-doped-ZnO semiconductor nanoparticles

The structural and dilute magnetic properties of (Co, Li) co-doped-ZnO semiconductor nanoparticles

Magnetic property and Mössbauer analysis of SrSn1−x Fe x O3 prepared by a sol-gel method

The dilute magnetic properties of SrSn1−xFexO3 (x = 0.01 − 0.15) prepared by sol-gel and thermal decomposition methods were investigated by 57Fe Mossbauer spectrometry, magnetometry, and X-ray diffractometry. It was found that SrSnO3 doped with 2–8 % Fe show weak ferromagnetism although only paramagnetic doublets are observed in 57Fe Mossbauer spectra at room temperature (RT), whereas SrSnO3 doped with 10–15 % Fe show relatively strong ferromagnetism, and the sextets are additionally observed in the 57Fe Mossbauer spectra at RT. The weak ferromagnetism by doping 2–8 % Fe is considered to be caused by the induced magnetic defects, and the ferromagnetism by doping 10–15 % Fe are considered mainly due to the magnetic coupling between dilute Fe 3+ partially substituted at Sn 4+ sites in the orthorhombic structure of SrSnO3−δ accompanying the oxygen deficiencies. It is further remarkable that poor crystalline 8 % Fe doped SrSnO3−δ obtained by annealing at 600 ∘C shows relatively high saturation magnetization and low coercivity.

The Dilute Magnetic Properties of Monolayer MoS<sub>2</sub> Doped with Transition Metal Fe and VA Atoms

The two-dimensional material MoS2 has attracted a growing attention due to its potential applications in electronic devices in recent years [1,2,3], and the monolayer MoS2 is a direct gap semiconductor with a band gap of 1.8eV [4]. In the existing studies, it has indicated that MoS2 can get an available magnetism with doping transition metal atoms [5], and is expected to be a new generation of diluted magnetic semiconductor (DMS) [6,7]. Moreover, we found that Fe-doped MoS2 could present a strong magnetism but a semimetal characteristic, losing its original semiconductor properties while obtaining magnetism. Therefore, it is necessary to explore some methods to make monolayer MoS2 exhibit both magnetic and semiconductor properties. In this paper, we propose the method of N, Fe atoms co-doping to achieve this objective. The structural, electronic and magnetic properties of MoS2 doped with transition metal Fe and VA atoms have been investigated by first principle calculations based on density functional theory. The 3×3×1 supercell of monolayer MoS2 as a calculation model has been used. The result shows that pure MoS2 has no magnetism, while Fe-doped MoS2 exhibits a good magnetism about 1.849μB but a semimetal characteristic. This is due to that Mo-4d, S-2p, Fe-3d states has a strong coupling around the Femi energy for the introduction of Fe atom, and the Femi energy only pass through the spin-up density of states. For the co-doping with VA atoms and Fe atoms, it is found that the magnetic moment of Fe-N, Fe-P and Fe-As co-doped MoS2 is 0.956μB, 0.775μB, 0.782μB. Moreover, the Fe-N co-doped MoS2 presents semiconductor characteristics, in contrast, Fe-P and Fe-As co-doped MoS2 appear semimetal properties. It indicates that the semimetal characteristic of Fe-doped MoS2 could change into indirect band gap semiconductor due to the introduction of N atom. The band gap is 0.2eV. Our study demonstrate that the method of Fe, N co-doping could make MoS2 have good magnetic and also semiconductor properties at the same time.

Dilute magnetic properties of Fe doped Al2O3 powders prepared by sol-gel method

Aluminium oxides doped with 1% 57Fe were prepared by sol-gel method, and annealed for 3 hours at various temperatures between 550°C and 1100°C. Amorphous phases were obtained below 1000°C, and crystalline α–Al2O3 was formed at 1100°C. Although Al2O3 itself shows diamagnetism, the light doping of Fe ions into aluminium oxide induced a very weak ferromagnetism, but the ferromagnetism disappeared by longer annealing. Mossbauer spectra were composed of paramagnetic Fe2 + and Fe3 + species for samples heated below 750°C, and of paramagnetic Fe3 + above 850°C, in addition to a magnetic sextet and relaxation peaks of Fe3 + . The magnetic and quadrupole interactions of the sextet and the relaxation peaks and the density functional calculations suggest that the lightly doped Fe3 + ions are substituted at Al sites in the Al2O3 lattice.