In this paper we report successful synthesis and magnetic properties of (Ca,Na)(Zn,Mn)2Sb2 as a new ferromagnetic dilute magnetic semiconductor (DMS). In this DMS material the concentration of magnetic moments can be controlled independently from the concentration of electric charge carriers that are required for mediating magnetic interactions between these moments. This feature allows us to separately investigate the effect of carriers and of spins on the ferromagnetic properties of this new DMS alloy, and particularly of the critical ferromagnetic behavior. We use modified Arrott plot technique to establish critical exponents b, g, and d of this alloy. We find that at low Mn concentrations (< 10 at.%), it is governed by short-range 3D-Ising behavior, with experimental values of b, g, and d very close to theoretical 3D-Ising values of 0.325, 1.24, and 4.815. However, as the Mn concentration increases, this DMS material exhibits a mixed-phase behavior, with g retaining its 3D-Ising characteristics, but b crossing over to longer-range mean-field behavior.
We propose a method to realize diluted magnetic semiconductors (DMS) with p- and n-type carriers by choosing host semiconductors with a narrow band gap. By employing a combination of the density function theory and quantum Monte Carlo simulation, we demonstrate such semiconductors using Mn-doped BaZn2As2, which has a band gap of 0.2 eV. In addition, we found a new non-toxic DMS Mn-doped BaZn2Sb2, of which the Curie temperature Tc is predicted to be higher than that of Mn-doped BaZn2As2, the Tc of which was up to 230 K in the recent experiment.
Towards a Fully Ab-Initio Description of the Diluted Magnetic Semiconductor $Ga_{1-x}Mn_{x}As$. Ferromagnetism, Electronic Structure, and Optical Response
Being a wide band gap system GaMnN attracted considerable interest after the discovery of highest reported ferromagnetic transition temperature $T_C$ $\sim$ 940 K among all diluted magnetic semiconductors. Later it become a debate due to the observation of either a ferromagnetic state with very low $T_C$ $\sim$ 8 K or sometimes no ferromagnetic state at all. We address these issues by calculating the ferromagnetic window, $T_C$ Vs $p$, within a $t-t'$ Kondo lattice model using a spin-fermion Monte-Carlo method on a simple cubic lattice. We exploit the next-nearest-neighbor hopping $t'$ to tune…
Single-Band Model for Diluted Magnetic Semiconductors: Dynamical and Transport Properties and Relevance of Clustered States
利用蒙特卡罗模拟研究了（III，Mn）V稀磁半导体（DMS）的单带自旋费米子晶格模型的动力学和输运性质.这项工作是以前工作的继续（G. Alvarez，Phys. Rev. Lett. 89，277202（2002）），其中研究了模型的静态性质。本文的结果支持了J/t（标准符号）的相关机制是中间耦合机制的观点，即载流子在Mn自旋附近仅被部分俘获，在居里温度T_C以上存在局部有序区域（团簇）。这一结论是基于电阻率随温度变化的计算，即在T_C附近出现软金属到绝缘体的转变，以及态密度和电导率的分析。此外，在集群制度中观察到一个大的磁阻模拟。DMS和锰氧化物之间的正式类比进行了讨论。
Recently a new type diluted magnetic semiconductor (BaK)(ZnMn)2As2 (BZA) with high Cure temperature (Tc) was discovered showing independent spin and charge doping mechanism. This makes BZA a promising material for spintronics devices. Here we report for the first time the successful growth of BZA single crystal. An Andreev reflection junction that can be used to evaluate spin polarization was fabricated based on the BZA single crystal, a 66% spin polarization of the BZA single crystal was hence obtained by Andreev reflection spectroscopy analysis.
IV-VI diluted magnetic semiconductor Ge1-xCrxTe layers up to x=0.1 were grown on SrF2 substrates by molecular beam epitaxy. In site reflection high-energy electron diffraction shows a streaky pattern with sixfold symmetry in the plane for the Ge1-xCrxTe layer, implying an epitaxial growth of Ge1-xCrxTe [111]/SrF2 [111]. A clear hysteresis loop is observed in the anomalous Hall effect measurements due to the strong spin-orbit interaction in the host GeTe. The Curie temperature increases with increasing Cr composition up to 200 K, but there is no clear dependence of the Curie temperature on the …
The DFT calculations were performed of densities of states of semiconductor GaAs and magnetic semiconductor Ga0.9375Mn0.0625As. It is obtained that a part of Mn3d- states is hybridized with valence band at Fermi level. The exchange integrals of Anderson impurity model were calculated making use of atomic Hartree-Fock package and angular momentum coupling technique. Theoretical Tc of Ga0.9375Mn0.0625As obtained in the multiscale ab initio method is in reasonable agreement with experiment. The application of Hubbard parameters in DFT calculations using ultrasoft pseudopotentials is discussed.
We report on study of magnetic impurities spin relaxation in diluted magnetic semiconductors above Curie temperature. Systems with a high concentration of magnetic impurities where magnetic correlations take place were studied. The developed theory assumes that main channel of spin relaxation is mobile carriers providing indirect interactions between magnetic impurities. Our theoretical model is supported by experimental measurements of manganese spin relaxation time in GaMnAs by means of spin-flip Raman scattering. It is found that with temperature increase spin relaxation rate of ferromagnet…
A systematic study of hole compensation effect on magnetic properties, which is controlled by defect compensation through ion irradiation, in (Ga,Mn)As, (In,Mn)As and (Ga,Mn)P is presented in this work. In all materials, both Curie temperature and magnetization decrease upon increasing the hole compensation, confirming the description of hole mediated ferromagnetism according to the p-d Zener model. The material dependence of Curie temperature and magnetization versus hole compensation reveals that the manipulation of magnetic properties in III-Mn-V dilute ferromagnetic semiconductors by ion i…
EPR and ferromagnetism in diluted magnetic semiconductor quantum wells
受调制掺杂的CdMnTe量子阱中的电子顺磁共振（EPR）谱的最新测量的启发，[F. J. Teran { \it et al.}，物理修订信函{ \bf 91}，077201（2003）]，我们发展了准二维稀磁半导体（DMS）中集体自旋激发的理论。我们的理论解释了在这些实验中发现的Mn离子的局部矩和巡回电子自旋之间的集体耦合的结果的巨大的奈特位移。我们用这个理论来讨论（II，Mn）VI量子阱中的铁磁性的物理，并推测它可能在n型调制掺杂系统中观察到的温度。
