Magnetic Resonance in ZnGeP2 and (Zn,Mn)GeP2

Electron paramagnetic (EPR) and ferromagnetic resonance (FMR) have been studied in the system of (Zn,Mn)GeP₂ ferromagnetic layer grown on undoped ZnGeP₂ single crystal. Strong FMR signals are registered in the wide temperature range up to room temperature. EPR and photo-EPR of intrinsic defects are observed in ZnGeP₂ substrate. EPR spectra characteristic of Mn²⁺ ions on Zn²⁺ sites in the bulk appear after the growth of the ferromagnetic layer on ZnGeP₂ crystal indicating the efficient Mn-diffusion into the bulk crystal by the annealing treatments.     

Magnetic Specific Heat of Heavily p-Type Doped (Zn,Mn)Te:P

The magnetic contribution to the specific heat of bulk crystals of Zn_1?x Mn _x Te ( x = 0.03) heavily (up to 10¹⁹ cm^?3) p-type doped with P is studied over the temperature range 0.5–15 K and magnetic field range 0–3 T. The magnetic specific heat observed at zero magnetic field indicates that a substantial part of the magnetic ions has the degeneracy of their magnetic ground state lifted by d–d and p–d exchange interactions. The effect increases for doped and annealed samples with higher concentration of conducting holes. We have also carried out a theoretical analysis that takes into account the contributions due to small magnetic clusters, single magnetic ions in crystal field of distorted crystal lattice, and low energy excitations of the p–d exchange-coupled system of local moments and carriers.     

Second-harmonic and sum-frequency generation in ZnGeP(2)

ZnGeP(2) has been found to be phase matchable for type-1 second-harmonic generation of a CO(2) laser to as high as 10.78 mum at 20.0 degrees C. The Sellmeier equations and nonlinear optical constant of this crystal are reported.     

Magnetic Specific Heat of Heavily p-Type Doped (Zn,Mn)Te:P

The magnetic contribution to the specific heat of bulk crystals of Zn_1–x Mn _x Te ( x = 0.03) heavily (up to 10¹⁹ cm^–3) p-type doped with P is studied over the temperature range 0.5–15 K and magnetic field range 0–3 T. The magnetic specific heat observed at zero magnetic field indicates that a substantial part of the magnetic ions has the degeneracy of their magnetic ground state lifted by d–d and p–d exchange interactions. The effect increases for doped and annealed samples with higher concentration of conducting holes. We have also carried out a theoretical analysis that takes into account the contributions due to small magnetic clusters, single magnetic ions in crystal field of distorted crystal lattice, and low energy excitations of the p–d exchange-coupled system of local moments and carriers.     

Spin Carrier Exchange Interactions in (Ga,Mn)N and (Zn,Co)O Wide Band Gap Diluted Magnetic Semiconductor Epilayers

(Ga,Mn)N and (Zn,Co)O wide band gap diluted magnetic semiconductor epilayers have been investigated by magneto-optical spectroscopy. In both cases, absorption bands observed below the energy gap allow us to study the nature of the valence and spin state of the incorporated magnetic element. Exchange interactions between magnetic ions and carriers can be observed by analyzing the magnetic circular dichroism in transmission or the exciton Zeeman splitting in reflection for (Zn,Co)O. A first estimation of the exchange integrals can be given for both materials.     

Compaction of homogeneous (Mn,Zn)-ferrite potcores

The compaction of thin-walled potcore compacts (height 10 mm, diameter 15 mm, wall thickness 1 mm) with a high homogeneity is analysed. High homogeneity implies that the density is uniform throughout the compact. In order to attain this goal, internal and external friction are minimized while the mode of pressing and pressing velocity are optimized. Internal friction refers to friction between the powder particles, which is influenced by the particle size distribution and additives. The use of five different additives is evaluated. External friction relates to the friction between the powder and the die wall, which is influenced by the relative hardness of the die wall and lubricants. The effects of three different coatings and a lubricant on friction with the die wall have been investigated. The homogeneity of compacts with complicated shapes is affected by the formation of large local density gradients, which lead to differential shrinkage during sintering. By characterizing the shape of sintered products, it is shown that the inhomogeneity in compacts is reduced by optimizing the pressing mode and the pressing velocity. This improves the variation of the diameter over the height of the sintered potcores from 3 to 1.0%     

Transient thermal lens in a ZnGeP(2) crystal

The first observations, to the authors' knowledge, of transient thermal lensing in a ZnGeP(2) crystal achieved with 2.09-μm laser excitation of 800-μs, 70-mJ pulses at 30 Hz and by burst-mode Q-switched pumping are presented. The laser power transmitted through an aperture was approximated by an adiabatic model with currently accepted values for the thermal properties of ZnGeP(2) and corresponded to focal-length changes from infinity to 10 cm during each 800-μs pulse. Similar results were seen when the crystal was operated as an optical parametric oscillator. This transient thermal lens severely limits ZnGeP(2) as a material for use in optical parametric oscillators for these modulated, high-power operating conditions.     

Spontaneous Polarization and Magnetic Investigation Of BiXO3 (X=Co,Mn, Fe,V, Zn): First-Principle Study

Spontaneous polarization and magnetic properties of BiXO3 with X = Co, Fe, Mn, V, and Zn have been studied using the full-potential, linear augmented plane wave (FP-LAPW) method with GGA and mBJ implemented in the WIEN2K code. The investigation shows that BiXO3 with X = Co, Fe, Mn, and Zn is stable in the antiferromagnetic state while for BiVO3, the magnetic stability was shown in the ferromagnetic state. The calculation shows the existence of a charge transfer between p states of oxygen and d states of Co and Fe for X = Co and Fe. The existence of Co, Fe, Mn, and V makes BiXO3 a non-absorbent compound. However, for Zn, the structure behaves as an absorbent compound especially in the visible light. We note that the spontaneous polarization is calculated with Berry phase BI and was found very close and comparable with other works.     

Element-specific electronic structure of Mn dopants and ferromagnetism of (Zn,Mn)O thin films

Element-specific electronic structure of (Zn,Mn)O thin films with various Mn concentrations has been investigated using X-ray absorption and emission spectroscopy. According to comparison between the experimental spectra and the density functional theory calculations (partial density of states and exchange interactions for various Mn defect configurations), the substitutional Mn impurities do not induce ferromagnetism in (Zn,Mn)O samples. The ferromagnetic properties can be obtained when defect configurations consisting of both substitutional and interstitial Mn atoms are present. The ferromagnetism in ZnO-based magnetic semiconductors is favored to be Ruderman-Kittel-Kasuya-Yoshida type and the established theoretical model is in a good agreement with the X-ray spectroscopic measurements.     

Magnetic and Magnetotransport Properties of Diluted Magnetic Semiconductor (Ga,Mn)Sb Crystals

We report the magnetic and magnetotransport properties of Ga_1−x Mn _x Sb crystals grown with different Mn doping concentrations (x=0.01, 0.02, 0.03 and 0.04) by the horizontal Bridgman technique. A systematic reduction in lattice parameter with increase in Mn concentration is observed through X-ray diffraction studies. The crystals show negative magnetoresistance and anomalous Hall effect below 10 K. Anomalous Hall coefficient is negative and decreases with increasing Mn concentration. Temperature dependence on magnetization measurement shows a magnetic ordering below 10 K which could arise from GaMnSb alloy formation. Also, ferromagnetism is observed till room temperature due to the presence of MnSb clusters. Existence of MnSb clusters is verified through scanning electron microscopy. The carrier concentration increases with Mn doping and this results in decrease of resistivity. The observed magnetic and transport properties indicate the presence of ferromagnetic phase below 10 K in the studied system.      

Template ion exchange route to nanocrystalline MIn2S4 (M=Mn,Zn)

A template ion exchange method has been established to synthesize ternary sulfides MIn₂S₄ (M=Mn, Zn) by the reaction of metal chlorides and NaInS₂ in absolute ethanol at 140 °C for 12 h. The effects of reactant NaInS₂, temperature and reaction time on the template ion exchange reaction were investigated.     

Mn0．8Zn0．2Fe2O4／MgAl-LDHs复合材料的磁性能和磁热效应

采用共沉淀法将纳米锰锌铁氧体粒子(Mn0.8Zn0.2Fe2O4)与镁铝双金属氢氧化物(MgAl-LDHs)进行组装合成了磁性纳米镁铝双金属氢氧化物,并通过TEM,FTIR、DTA、XRD、VSM等方法对其进行表征.样品的结构分析结果表明,复合材料具有典型的核壳结构,镁铝双金属氢氧化物被赋予磁性后并没有改变其层状结构的典型特征.样品的磁学性能和磁热性能测试结果表明,铁氧体的含量对复合材料的磁性能和磁热效应起着决定性作用;MgAl-LDHs对铁氧体粒子没有显著的磁屏蔽效应,复合材料的饱和磁化强度与铁氧体的含量呈正线性相关,而复合材料的矫顽力随MgAl-LDHs含量的增加呈现先减小后增大的趋势,但整体变化幅度很小,同时MgAl-LDHs对铁氧体粒子磁热效应的影响也极小.     

Strain-Controlled Variation of Magnetoresistive and Magnetic Anisotropy in (Ga,Mn)As

The influence of strain on the anisotropic magnetoresistance (AMR) and magnetic anisotropy (MA) of (Ga,Mn)As is systematically investigated in layers grown on relaxed (In,Ga)As/GaAs templates. By choosing different In contents, the vertical strain ε _zz in the (Ga,Mn)As layers could be varied over a wide range from tensile to compressive, including the case of (nearly) zero strain. The AMR and the MA of the as-grown and annealed samples were probed at 4.2 K by means of angle-dependent magnetotransport measurements. The respective resistivity and anisotropy parameters, determined by an appropriate fitting procedure, were found to linearly vary with ε _zz . The MA was additionally manipulated by preparing narrow stripes from the (Ga,Mn)As layers, resulting in an in-plane uniaxial contribution to the free energy, which is not present in unstrained samples.     

Heterogeneous equilibria in the system uranoborate MII(BUO5)2 · nH2O-aqueous solution (MII=Mn, Co, Ni, Zn)

Solutions of uranoborates M^II(BUO₅)₂·nH₂O (M^II=Mn, Co, Ni, Zn) in aqueous mineral acids at 25°C are studied. Based on experimental data on the solubility of uranoborates in hydrochloric acid, a quantitative model of the system crystalline uranoborate-aqueous solution is suggested. The model is used to predict the state of the investigated heterogeneous systems under various conditions, and also to estimate the standard thermodynamic functions of the indicated series of uranoborates.     

Hydrogenation of the Laves Phases of Gd(Mn,Al)2, Tb(Mn,Al)2, and Tb(Fe,Al)2 Compounds

We study the formation of the AB₂ Laves phases in RE–M–Al (where RE is Gd or Tb and M is Fe or Mn) systems and determine their hydrogen-sorption properties. The crystal structures of the original compounds and their saturated hydrides are studied by the X-ray powder diffraction method. It is shown that these compounds absorb hydrogen at pressures of 0.1–0.12 MPa without amorphization and their hydrogen-sorption ability decreases as the amount of aluminum in the compound increases.     

(Ga,Mn)As稀磁半导体的杂质动力学模拟研究

结合第一性原理计算和动力学蒙特卡罗模拟研究了稀磁半导体(Ga,Mn)As中Mn杂质的沉积动力学规律。利用第一性原理计算和爬坡弹性带方法计算了Mn杂质的跃迁势垒和结合能,并把这些能量作为动力学蒙特卡罗模拟(Ga,Mn)As微观结构演化的输入数据。结果表明在外延生长退火下长时间的微观结构演化的背后机制是Ga空位调节Mn原子在Ga子晶格上进行扩散。这种扩散会导致Mn原子的聚集,进而降低了居里温度。此外,随着退火温度的升高Mn团簇聚集的速率也更快。在高温退火下容易导致相分离。     

Magnetic Anisotropies and (Ga,Mn)As‐based Spintronic Devices

In this Review, we discuss the rich anisotropic properties of the ferromagnetic semiconductor (Ga,Mn)As, and their implications in transport studies. We review the various sources and types of anisotropy seen in the material, discuss its magnetization reversal process, and demonstrate how basic transport properties, such as resistivity and Hall measurements, can be used as very sensitive tools to investigate the magnetization properties of the material. We also discuss how the magnetic anisotropy, coupled with large spin–orbit coupling, leads to an anisotropy in the transport density of states, which in turn leads to fundamentally novel behavior such as tunneling anisotropic magnetoresistance (TAMR).     

Ferromagnetism from Acceptors of Native Point Defects in (Zn, Mn)O Doped Systems

In this paper, we represent a theoretical study of the (Zn, Mn)O doped system with native point defects of ZnO as oxygen interstitials (O_i) and zinc vacancies (V_Zn). Under these defects, it has been shown that the ground state can be converted from spin glass to ferromagnetic phase, by performing ab initio density functional theory calculations relying on the Korringa?CKohn?CRostoker coherent potential approximation (KKR-CPA) method employing the local density approximation (LDA) with the parameterization by Morruzi, Janak, and Williams. The stability of magnetism in the (Zn, Mn)O doped system with different native point defects has been discussed. We find that acceptor-like defects (that is, O_i, O_Zn, and V_Zn) may cause the enhancement of the ferromagnetic characteristics in ZnMnO with increasing T _c . Based on the theoretical results, we suggest that the native point defects have a key role with respects to the FM properties. Using the mean field approximation, the Curie temperature in our studied model is estimated.