Mn Sb Research Articles

Role of the underlying layer in crystalline structure and magnetic properties of Mn–Sb–Bi thin film

Mn–Sb–Bi thin films were grown by deposition of Mn onto the annealed Sb/Bi bilayer. Changes in the morphology and structure of the films both as-sputtered and after annealing at 623 K for 5 h were observed. Annealing the Sb/Bi bilayer causes the Sb–Bi alloy with enlarged grains. Annealing Mn/(Sb–Bi) films shows a relatively high saturation magnetization, a small in-plane coercivity. The existence of the (001) orientation in the as-sputtered film produced by the intermediate annealing results in the better (001) orientation of the NiAs-type Mn–Sb–Bi phase in an annealed Mn/(Sb–Bi) thin film. The film shows the existence of the perpendicular anisotropy component.

Pressure-induced ferromagnetism in (In,Mn)Sb dilute magnetic semiconductor

Recent advances in III(1-x)Mn(x)V ferromagnetic semiconductors (for example in Ga(1-x)Mn(x)As) have demonstrated that electrical control of their spin properties can be used for manipulation and detection of magnetic signals. The Mn(2+) ions in these alloys provide magnetic moments, and at the same time act as a source of valence-band holes that mediate the Mn(2+)-Mn(2+) interactions. This coupling results in the ferromagnetic phase. In earlier workit was shown that the ferromagnetic state can be enhanced or suppressed by varying the carrier density. Here we demonstrate that, by using hydrostatic pressure to continuously tune the wavefunction overlap, one can control the strength of ferromagnetic coupling without any change in the carrier concentration. Tuning the exchange coupling by this process increases the magnetization spectacularly, and can even induce the ferromagnetic phase in an initially paramagnetic alloy. These results may open new directions for strain-engineering of nanodevices.

Exchange Interactions and Curie Temperatures in Dilute Magnetic Semiconductors

We discuss the origin of ferromagnetism in dilute magnetic semiconductors based on ab initio calculations for Mn-doped GaN, GaP, GaAs and GaSb. We use the Korringa-Kohn- Rostoker method in connection with the coherent potential approximation to describe the substitutional and moment disorder. Curie temperatures (T C) are calculated from first-principles by using a mapping on a Heisenberg model in a mean field approximation. It is found that if impurity bands are formed in the gap, as it is the case for (Ga, Mn)N, double exchange dominates leading to a characteristic √c dependence of T C as a function of the Mn concentration c. On the other hand, if the d-states are localized, as in (Ga, Mn)Sb, Zener’s p-d exchange prevails resulting in a linear c-dependence of T C. In order to have more precise estimations of T C, effective exchange coupling constants J ij’s are calculated by using the formula of Liechtenstein et al. It is found that the range of the exchange interaction in (Ga, Mn)N is very short. On the other hand, in (Ga, Mn)As the interaction is weaker but long ranged. Monte Carlo simulations show that the T C values of (Ga, Mn)N are very low since percolation is difficult to achieve for small concentrations and the mean field approximation strongly overestimates T C. Even in (Ga, Mn)As the percolation effect is still important.

Effect of hydrostatic pressure on the transport properties in magnetic semiconductors

The effect of pressure on the ferromagnetic phase transition has been studied in manganese doped III-V semiconductors by electrical conductance and Hall measurements. We found that the application of hydrostatic pressure shifts the transition temperature upwards both in (In,Mn)Sb and (Ga,Mn)As. The anomalous-Hall coefficient shows a dramatic increase in the hysteresis loops in the ferromagnetic phase and an enhanced magnetization both below and above the phase transition. As the normal-Hall results suggest that the pressure does not change the carrier density [in (In,Mn)Sb] or rather decreases it [in (Ga,Mn)As], all the above observations are indicative of a pressure-induced enhancement of magnetic coupling.

Exchange interactions in diluted magnetic semiconductors

On the basis of ab initio calculations for Mn-doped GaN, GaP, GaAs and GaSb, wediscuss the origin of ferromagnetism in diluted magnetic semiconductors. Thecalculations use the Korringa–Kohn–Rostoker method in connection with the coherentpotential approximation to describe the substitutional and moment disorder. Bymapping the total energy results onto a Heisenberg model, the Curie temperatureTC is estimated in the mean field approximation (MFA). If impurity bands are formed in thegap, as is the case for (Ga, Mn)N, double exchange dominates leading to a characteristic dependence of TCMFA as a functionof the Mn concentration c. On the other hand, if the d states are localized, as in (Ga, Mn)Sb, Zener’s p–d exchange prevails, resultingin a linear c dependence of TCMFA. (Ga, Mn)As is an intermediate case, showing a -like behaviour in the local density approximation (LDA), but a nearly linearc dependence, ifthe more accurate LDA +U method with U = 4 eV is used.

Investigation of magnetic properties in Mn incorporated InSb, InP, and GaAs, synthesized through controlled-ambient annealing

AbstractMagnetic semiconductors are of interest for emerging spintronic applications, such as the integration of electronic information processing with magnetic data storage. We report on a new approach - furnace annealing under controlled ambients – aimed at increasing Mn incorporation and synthesizing new magnetic semiconductors with Tc greater than/around room temperature. These annealing treatments are hypothesized to reduce the effect of Mn interstitials. We have obtained preliminary SQUID magnetometry results which indicate ferromagnetic Curie temperatures of around 130 K in (In,Mn) Sb and 60 K in (In, Mn)P. X-ray diffraction was used to characterize phase homogeneity.

Magnetic impurities and materials design for semiconductor spintronics

Curie temperatures (TC) of several diluted magnetic semiconductors are calculated from first-principles by using a mapping on a Heisenberg model in a mean field approximation. Very large TC’s are obtained for V- or Cr-doped ZnSe and ZnTe and Cr-doped GaN, GaP and GaAs. Effects of additional carrier doping into (Ga, Mn)As and (Ga, Mn)N are investigated. TC of (Ga, Mn)N increases by hole doping, while (Ga, Mn)As is insensitive to hole doping. The origin of the ferromagnetism in Mn-doped III–V DMS is also discussed. It is found that if impurity bands are formed in the gap, as it is the case for (Ga, Mn)N, double exchange dominates leading to a characteristic √c dependence of TC as a function of the Mn concentration c. On the other hand, if the d-states are localized, as in (Ga, Mn)Sb, Zener’s p–d exchange prevails resulting in a linear c-dependence of TC. (Ga, Mn)As is an intermediate case, showing a √c like behavior in the Local density approximation (LDA), but a nearly linear c-dependence, if the LDA+U method, with U=4eV, is used.

Carrier-induced ferromagnetic order in the narrow gap III–V magnetic alloy semiconductor (In,Mn)Sb

Preparation and physical properties of p- and n-InMnSb epitaxial films with Mn contents up to 10% were studied with the aim of seeking phenomena induced by the spin exchange interaction between carrier and Mn spins. For p-type samples with Mn eff=4.5×10 20 and p=1.1×10 20 cm −3 , carrier-induced ferromagnetic order with a Curie temperature of 20 K was observed. The sign of the anomalous Hall coefficient is found to be negative. Tellurium-doped n-type samples (n=8.6×10 18 cm −3) with net Mn contents of 10% are found to be paramagnetic.

Spin polarization and magnetotransport of Mn–Sb alloys in magnetic tunnel junctions

The spin polarization of MnxSb1−x for x=0.35–0.45 has been explored via magnetic tunnel junctions using CoFe counterelectrodes and via superconducting tunneling spectroscopy using Al counterelectrodes. MnxSb1−x with x∼0.45 shows a tunneling spin polarization of ∼30% at 0.25 K, and a tunneling magnetoresistance of ∼18% at 10 K both of which are very similar to previously reported data on NiMnSb alloys. These results support the notion that surface segregation of Mn and Sb reduces the spin polarization of the purported half-metal NiMnSb.

Eu10Mn6Sb13: a new ternary rare-Earth transition-metal Zintl phase.

A new transition-metal-containing Zintl compound, Eu(10)Mn(6)Sb(13), was prepared by a high-temperature Sn-flux synthesis. The structure was determined by single-crystal X-ray diffraction. Eu(10)Mn(6)Sb(13) crystallizes in the monoclinic space group C2/m with a = 15.1791(6) A, b = 19.1919(7) A, c = 12.2679(4) A, beta = 108.078(1)*, Z = 4 (R1 = 0.0410, wR2 = 0.0920), and T = 90(2) K. The structure of Eu(10)Mn(6)Sb(13) is composed of double layers of Mn-centered tetrahedra separated by Eu(2+) cations. The double layers are composed of edge- and corner-sharing Mn-centered tetrahedra which form cavities occupied by Eu(2+) cations and [Sb(2)](4-) dumbbells. Linear [Sb(3)](5-) trimers bridging two tetrahedra across the cavity are also present. Bulk susceptibility data indicate paramagnetic behavior with a ferromagnetic component present below 60 K. Temperature-dependent electrical resistivity measurements show semiconducting behavior above 60 K (E(a)() = 0.115(2) eV), a large and unusually sharp maximum in the resistivity at approximately 40 K, and metallic behavior below 40 K. (151)Eu Mössbauer spectra confirm that the europium is divalent with an average isomer shift of -11.2(1) mm/s at 100 K; the spectra obtained below 40 K reveal magnetic ordering of six of the seven europium sublattices and, at 4.2 K, complete ordering of the seven europium sublattices.

In 1−x Mn x Sb —a narrow-gap ferromagnetic semiconductor

A narrow-gap ferromagnetic In1−xMnxSb semiconductor alloy was grown by low-temperature molecular-beam epitaxy on CdTe/GaAs hybrid substrates. Ferromagnetic order in In1−xMnxSb was unambiguously established by the observation of clear hysteresis loops both in direct magnetization measurements and in the anomalous Hall effect, with Curie temperatures TC ranging up to 8.5 K. The observed values of TC agree well with the existing models of carrier-induced ferromagnetism.

The Ternary System Au—Mn—Sb and the AuMnSn1‐xSbx Phase.

Abstract The phase relations in the Au–Mn–Sb system have been studied by powder X-ray diffraction, metallography, electron microprobe analysis, and thermal analysis. The condensed phases occurring, tie-lines, and tie-triangles are presented for an isothermal section of the phase diagram at 400 °C. At this temperature the solid solubility of the third component in the binary phases is generally limited to a few percent. The phase relations are relatively complex in regions which involve the numerous binary gold–manganese phases. The only genuine ternary phase, AuMnSb, has a very narrow composition range around Au 35 Mn 30 Sb 35 and is stable up to 575±5 °C, where it decomposes peritectically. The AuMnSb phase is ferromagnetic with a Curie temperature of 135±10 K. The solid-solution phase AuMnSn 1− x Sb x exhibits ferromagnetic properties throughout the entire homogeneity range with the Curie temperature ranging between 625±100 and 135±10 K.

The optical and magneto-optical properties of MnSbBi films

Abstract The optical and magneto-optical properties of Mn(Sb 1− x Bi x ) films were investigated for incident photons within the energy range from 1.3 to 4.0 eV. The diagonal and off-diagonal optical conductivities were determined from the results of spectroscopic ellipsometry and the polar Kerr effect measurements. A large Kerr rotation angle of about 0.57° was observed at photon energy ℏ ω ≈2.65 eV for the Mn 55 Sb 36 Bi 9 film with an average grain size of 30 nm. The changes of the exchange splitting and the spin–orbit interaction strength are responsible for the strong spectral dependence of the Kerr effect in Mn(Sb 1− x Bi x ) nanocrystalline films.

The ternary system Au–Mn–Sb and the AuMnSn 1− xSb x phase

The phase relations in the Au–Mn–Sb system have been studied by powder X-ray diffraction, metallography, electron microprobe analysis, and thermal analysis. The condensed phases occurring, tie-lines, and tie-triangles are presented for an isothermal section of the phase diagram at 400 °C. At this temperature the solid solubility of the third component in the binary phases is generally limited to a few percent. The phase relations are relatively complex in regions which involve the numerous binary gold–manganese phases. The only genuine ternary phase, AuMnSb, has a very narrow composition range around Au 35Mn 30Sb 35 and is stable up to 575±5 °C, where it decomposes peritectically. The AuMnSb phase is ferromagnetic with a Curie temperature of 135±10 K. The solid-solution phase AuMnSn 1− x Sb x exhibits ferromagnetic properties throughout the entire homogeneity range with the Curie temperature ranging between 625±100 and 135±10 K.

Formation of MnSb during the growth of MnSi layers in the presence of an Sb flux

Structural and compositional analyses of a MnSi layer have been performed to elucidate the growth mechanism. The MnSi layer was grown by reactive deposition epitaxy in the presence of an Sb flux. The existence of Sb was found at the MnSi/Si interface and on the surface of MnSi layer by secondary ion mass spectrometry. In addition, x-ray photoelectron spectroscopy measurement shows that MnSb is formed on the surface of the grown MnSi layer. On the atomic scale, scanning transmission electron microscopy observations reveal the existence of an Sb–Mn–Sb structure at the interface between the MnSi layer and the Si substrate. The formation of the MnSb plays an important role for the improvement of crystalline quality of the silicide layer, acting both as a surfactant and as a compliant substrate for stress relief.

Crystalline structure and magnetic and magneto-optical properties of MnSbBi thin films

Mn–Sb–Bi thin films were prepared by successive r.f. or d.c. sputter deposition of elements in a trilayer configuration with either Bi or Sb as the first layer. In-situ transmission electron microscopy (TEM) observations were conducted to investigate the morphology and structure of the films, both as-deposited and after annealing at 623 K for 5 h in a high vacuum furnace. The morphology and structure of all the films are highly dependent on the first-deposited layer. For the annealed film in the configuration of Mn/Bi/Sb// a well-defined hexagonal Mn–Sb–Bi NiAs type structure with the c-axis perpendicular to the film surface was observed. The grain size (100 nm) was two times larger than that of the film having Bi as the first layer. In both kinds of film the easy direction of magnetisation was very close to the film plane. The polar Kerr rotation from the two film structures was approximately 1.0°.

ChemInform Abstract: Interaction Between Components in the Ti—Mn—Sb System at 870 K and the Physical Properties of Ti5Mn0.45Sb2.55.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

V–Mn–{Sn,Sb} ternary systems

The isothermal section of the phase diagrams of ternary V–Mn–Sn and V–Mn–Sb systems has been investigated at 770 and 870 K, respectively. No ternary compounds were observed. The systems are characterised by the existence of solid solutions based on the binary compounds. The temperature dependence of the electrical resistivity and differential thermopower for (V,Mn) 3Sb solid solution has been measured.

Interaction between components in the Ti–Mn–Sb system at 870 K and the physical properties of Ti 5Mn 0.45Sb 2.55

The isothermal section of the phase diagram at 870 K of the ternary Ti–Mn–Sb system was investigated. The existence of a new ternary compound, Ti 5Mn 0.45Sb 2.45, was revealed crystallizing in the W 5Si 3-type tetragonal structure (space group I4/mcm) with lattice parameters a=1.0462(1) nm and c=0.52776(3) nm. This compound has been characterized by measurements of the electrical resistivity, thermopower, and magnetic susceptibility over a wide temperature range and the EPR spectrum at room temperature.

ChemInform Abstract: Hypervalent Bonding in One, Two, and Three Dimensions: Extending the Zintl-Klemm Concept to Nonclassical Electron-Rich Networks

We construct a theory for electron-rich polyanionic networks in the intermetallic compounds of heavy late main group elements, building a bonding framework that makes a connection to well-understood hypervalent bonding in small molecules such as XeF(4), XeF(2), and I(3)(-). What we do is similar in spirit to the analogy between the Zintl-Klemm treatment of classical polyanionic networks and the octet rule for molecules. We show that the optimal electron count for a linear chain of a heavy main group element is seven electrons per atom, six electrons per atom for a square lattice, and five electrons per atom for a simple cubic lattice. Suggestions that these electron counts are appropriate already exist in the literature. We also derive electron counts for more complicated topologies, including one-dimensional ladders and one dimensional strips cut from a square lattice. We also study pairing (Peierls) distortions from these ideal geometries as well as other deformations. The presence of s-p mixing (or its absence) plays a critical role in the propensity for pairing and, in general, in determining the geometrical and electronic structure of these phases. Hypervalent bonding goes along with the relative absence of significant s-p interaction; there is a continuum of such mixing, but also a significant difference between the second-row and heavier elements. We attribute the existence of undistorted metallic networks of the latter elements to diminished s-p mixing, which in turn is due to the contraction of less-screened s orbitals relative to p orbitals down the groups in the Periodic Table. The number of electrons in the polyanionic network may be varied experimentally. An important general principle emerges from our theoretical analysis: upon oxidation a hypervalent structure transforms into a classical one with the same lattice dimensionality, while upon Peierls distortion the hypervalent structures transform into classical ones with the lattice dimensionality reduced. Dozens of crystal structure types, seemingly unrelated to each other, may be understood using the unifying concept of electron-rich multicenter bonding. Antimonides, which are explored in great detail in the current work, conform particularly well to the set of electron counting rules for electron-rich nonclassical networks. Some deviation up and down from the ideal electron count is exhibited by known stannides and tellurides. We can also make sense of the bonding in substantially more complicated alloys, including La(12)Mn(2)Sb(30) and Tl(4)SnTe(3). The hypervalent electron counting scheme developed in this paper, along with the classical Zintl-Klemm electron counting rules, gives an easy qualitative understanding of bonding in a wide variety of intermetallic compounds of heavy main group elements.