MnSb Phases Research Articles

Effect of a high-gradient magnetic field on grain refinement of a hypoeutectic Mn–Sb alloy during directional solidification

The obvious grain refinement of the primary MnSb phase has been observed in the Mn–89.7 wt% Sb alloy directionally solidified under a high-gradient magnetic field. With the application of a high-gradient magnetic field, the morphology of the primary MnSb phase transformed from developed dendritic-like to equiaxed-like, and the grain size decreased by approximately 93%. Refinement of the primary MnSb phase can be attributed to the constituent supercooling in front of the solidification interface, which promoted nucleation of the primary MnSb phase. The constituent supercooling can be linked to the enrichment of the Mn solute induced by the magnetic force and the Lorentz force that drove Mn solute migration and suppressed convection.

Characterization of the quenched GaSb–MnSb composites with high fraction of the ferromagnetic component

In this work, we studied properties of the GaSb–MnSb composite (30 mol.% GaSb ＋ 70 mol.% MnSb), synthesized from a melt of elemental precursors and subjected to the post-growth quenching procedure. We used a combination of experimental methods to specify phase composition of studied systems and elemental composition of each phase. Presented results suggest that studied composites can be considered as an ensemble of large ferromagnetic MnSb inclusions (with sizes of order of 10 μm) embedded in GaSb matrix with small amount of diluted Mn atoms in it. We show that magnetic and magnetooptical properties of composites are primarily defined by the MnSb phase. However, transport and magnetotransport properties of GaSb-MnSb samples depends on both components. In general, low temperature magnetotransport is dominated by the contribution of the GaSb matrix, while at room temperature measured data are qualitatively similar to those for pristine MnSb polycrystals. Additive character of these contributions along with the absence of any magnetooptical response besides that characteristic for bulk MnSb polycrystals suggests that these composites do not contain any considerable fraction of nm-sized ferromagnetic inclusions. Nevertheless, our results suggests that bulk GaSb–MnSb nanocomposite can be obtained, e.g. by more aggressive quenching.

Synthesis of bulk crystals and thin films of the ferromagnetic MnSb

High-temperature ferromagnets are widely used on a practical level. Based on them, magnetic memory for computers and various types of magnetic field sensors are created. Therefore, bulk ingots and thin-film samples of ferromagnet manganese antimonide (MnSb) with a high Curie point are of great interest, both from the practical and fundamental sides. Manganese antimonide films are obtained in hybrid structures using molecular-beam epitaxy. The thickness of the films does not exceed tens of nanometers. Despite their high sensitivity to magnetic fields, their small thickness prevents them from being used as magnetic field sensors. The aim of this work was to synthesise thick bulk ingots of manganese antimonide crystalsand films with a thickness of ~ 400 nm on sitall and silicon substrates. MnSb crystals were synthesised using the vacuum-ampoule method and identified using XRD, DTA, and microstructural analysis. The results of studies of bulk samples indicated the presence of an insignificant amount of antimony in additionto the MnSb phase. According to the DTA thermogram of the MnSb alloy, a small endothermic effect was observed at 572 °C, which corresponds to the melting of the eutectic on the part of antimony in the Mn-Sb system. Such composition, according to previous studies, guaranteed the production of manganese antimonide with the maximum Curie temperature. A study of the magnetic properties showed that the synthesised MnSb crystals were a soft ferromagnet with the Curie point ~ 587 K. Thin MnSb films were obtained by an original method using separate sequential deposition in a high vacuum of the Mnand Sb metals with their subsequent annealing. To optimise the process of obtaining films with stoichiometric composition, the dependences of the thickness of metal films on the parameters of the deposition process were calculated. The temperature range of annealing at which the metals interact with the formation of ferromagnetic MnSb films was established, the films were identified, and their electrical and magnetic properties were measured

Low-field reversible magnetocaloric effect in Co-dopedMn-Cr-Sb alloys

The magnetic phase transition and magnetocaloric effect in the Mn1.89− x Cr0.11Co x Sb ( x =0, 0.04, 0.06) alloys were studied in this work. Results show that the alloys undergo the first-order magneto-elastic phase transition from ferrimagnetic phase to antiferromagnetic phase on cooling, with very narrow thermal hysteresis, i.e., 3–4 K. Co doping cannot only enhance the transformation temperatures of magneto-elastic phase transition, but also avoid the formation of unfavorable MnSb phase. Direct measurements on the adiabatic temperature change ∆ T ad are employed to evaluate the magnetocaloric properties for the studied alloys. Under the field change of 1.5 T, the maximum ∆ T ad up to −1.4 K and the reversible ∆ T ad of −1.2 K can be achieved in the Mn1.85Cr0.11Co0.04Sb alloy. The combination of very small thermal hysteresis and large low-field reversible magnetocaloric effect makes the present alloys very attractive for the potential applications in magnetic refrigeration.

Crystallographic orientation of primary and eutectic phases in a hypoeutectic Mn–Sb alloy induced by solidification in high magnetic fields

This paper investigates how applying high magnetic fields influences the crystallographic orientations of the primary and eutectic phases, and their relationship, in a binary eutectic alloy. At 0 T, the primary MnSb phase in hypoeutectic Mn–Sb showed a random orientation, but at 3, 6, 9 and 11.5 T, its c axis was perpendicular to the magnetic field direction. In all cases, the eutectic MnSb phases showed the same orientations as their neighboring primary MnSb phase, on which they nucleated and grew. With high magnetic fields, the c axes of the eutectic and primary MnSb phases were oriented perpendicular to the magnetic field direction. The results show that applying a high magnetic field during solidification is a way of controlling the crystallographic orientation of both the primary and the eutectic phases in eutectic alloys.

Phonon properties of ZnSnSb2 + Mn semiconductors: Raman spectroscopy

AbstractDoping of II–IV–V2 semiconductors opens up new opportunities for wide application. Addition of Mn to these materials induces formation of magnetic clusters, which are responsible for high‐temperature ferromagnetism. Our aim was to examine how the addition of Mn influences the optical and structural properties of ZnSnSb2 by micro‐Raman spectroscopy. For four samples of Zn1 − xMnxSnSb2 synthesized using the direct fusion method, with x = 0.027, 0.066, 0.076, and 0.086, Raman spectra were measured at room temperature in spectral range from 60 to 300 cm−1. The obtained results indicate that these are multiphase materials. Based on the size and shape of complex microstructures, which consist of different phases and clusters, dispersive and duplex or triplex types of microstructures can be identified. Existence of ZnSb, SnSb, and MnSb phases was confirmed. By analyzing the Raman spectra, phonons of ZnSb and SnSb are determined and they are consistent with the data from literature. Phonon properties of ZnSnSb2, as well as of MnSb, are experimentally obtained for the first time. On the basis of a shift of the ZnSnSb2 phonons, we found that some amount of Mn entered lattice and form Zn1 − xMnxSnSb2. Microstructures affect the physical properties and behavior of a material. Analysis of this complex semiconductors and obtained results are important for their optimization and customization for possible applications.

In situ preparation of symmetrically graded microstructures by solidification in high-gradient magnetic field after melt and partial-melt processes

The effect of a symmetrically distributed magnetic-field gradient on the microstructure and magnetic properties of solidified and semi-solid isothermally annealed Mn–89.7 wt%Sb alloy was investigated experimentally. In the absence of an applied magnetic field, primary MnSb phases had a dendritic morphology after solidification. The content of primary MnSb-phase dendrites in the lower part of the sample decreased slightly with depth. After semi-solid isothermal annealing treatment, primary MnSb phase particles in the MnSb/Sb eutectic matrix were relatively evenly distributed along the vertical axis of the sample. The application of a symmetrical high magnetic-field gradient caused primary MnSb-phase dendrites and alloy particles to distribute along the middle of the sample with a symmetrical gradient. The content of primary MnSb-phase dendrites and particles first increased and then decreased along the vertical axis of the sample. The saturation magnetization of this alloy is related to its MnSb phase content. Therefore, the saturation magnetization of the Mn–89.7 wt%Sb alloy samples that were solidified and semi-solidly isothermally annealed under a symmetrical magnetic-field gradient increased and then decreased along the vertical axis of the sample. This symmetrical distribution of the saturation magnetization intensity was caused by the magnetic force driving the Mn-enriched zone or MnSb particles towards the center of the specimen.

Experimental Investigation of the Binary Mn-Sb Phase Diagram

The binary manganese-antimony (Mn-Sb) phase diagram was reinvestigated in the whole composition range using powder-XRD, DTA and SEM-EDX. The phase boundaries and melting temperatures of the ferromagnetic phases MnSb and Mn2Sb were modified by taking into account the new experimental data. Most of the reaction temperatures could be verified within a range of ±10 °C. Nevertheless, a few temperatures had to be revised, such as the eutectic reaction L → β-Mn + Mn 2 Sb at 893 °C and the eutectoid reaction β-Mn → α-Mn + Mn 2 Sb at 718 °C. The previously reported peritectic melting behavior of MnSb could be confirmed. The variation of the lattice parameters of the NiAs-(B8 1 ) type MnSb phase with composition was determined. A revised version of the of the Mn-Sb phase diagram is presented.

Growth of eutectic composites in the InSb–MnSb system

Eutectic composites in the InSb–MnSb system have been grown by the Bridgman method in vertical geometry using a growth charge of eutectic composition. The composites consisted of a [110]-oriented single-crystal InSb matrix and single-crystal MnSb needles aligned in the growth direction. As the solidification rate was raised from 0.5 to 6 mm/h, the length of the needles increased, whereas their diameter dropped from 20 to 4 µm. Further raising the solidification rate led to spontaneous crystallization. Characteristically, the electrical and magnetic properties of the eutectic composites in the InSb–MnSb system were found to exhibit large anisotropy. The low-temperature resistivity of the composites across the needles is four to five times that along the needles. With increasing temperature, the resistivity ratio drops by up to a factor of 2–3. This can be accounted for in terms of a geometric factor. The electrical conductivity of the composites is determined primarily by the MnSb phase, whose volume along the growth direction was considerably larger. According to magnetic measurements, the eutectic composites in the InSb–MnSb system are ferromagnets with a Curie temperature of ≃ 600 K.

Molecular-beam epitaxy of high-quality diluted magnetic semiconductor (Ga, Mn)Sb single-crystalline films

Diluted magnetic semiconductor (Ga, Mn)Sb and its related hetero-structures have attracted much attention in recent years since they are predicted to have some novel properties, such as the quantum anomalous Hall effect etc. However, it is not easy to grow high-quality (Ga, Mn)Sb films due to their narrow growth window. In this article, a series of 10 nm thick (Ga, Mn)Sb films with different Mn contents from 0.016 to 0.039 have been grown by molecular-beam epitaxy at low temperaturs (～230 ℃). The films have high crystalline quality as confirmed by in situ reflection high-energy electron diffraction and ex situ atomic force microscopy, and no MnSb phase could be observed. Curie temperature up to 30 K has been obtained in one (Ga, Mn)Sb film after post-growth thermal annealing. The magneto-resistance and anomalous Hall effect of this film have also been investigated at different temperatures.

Structural and magnetic properties of In1−xMnxSb: Effect of Mn complexes and MnSb nanoprecipitates

Structural and magnetic properties of the group III-V diluted magnetic semiconductor In1−xMnxSb with x = 0.005–0.06, including the nuclear magnetic resonance (NMR) investigations, are reported. Polycrystalline In1−xMnxSb samples were prepared by direct alloying of indium antimonide, manganese and antimony, followed by a fast cooling of the melt with a rate of 10–12 K/s. According to the X-ray diffraction data, part of Mn is substituted for In, forming the In1−xMnxSb matrix. Atomic force microscopy and scanning tunneling microscopy investigations provide evidence for the presence of microcrystalline MnSb inclusions (precipitates), having a size of ∼100–600 nm, and the fine structure of nanosize grains with a Gaussian distribution around the diameter of ∼24 nm. According to the NMR spectra, the majority of Mn enters the MnSb inclusions. In addition to the single Mn ions, which contribute to the magnetization M (T) only in the low-temperature limit of T < 10–20 K, and MnSb nanoprecipitates responsible for the ferromagnetic (FM) properties of In1−xMnxSb, a superparamagnetic (SP) contribution of atomic-size magnetic Mn complexes (presumably dimers) has been established. The fraction of the MnSb phase, η ∼ 1–4%, as well as the concentration, nsp ∼ (0.8–3.2) × 1019 cm−3, and the magnetic moment of the Mn dimers, μ ∼ 8–9 μB, are determined. The solubility limit of Mn in the InSb matrix, NSL ∼ 1020 cm−3, is estimated. Hysteresis in low (H < 500 Oe) magnetic fields and saturation of the magnetization in high (H > 20 kOe) magnetic fields are observed, indicating a presence of the SP and FM contributions to the dependence of M (H) up to T ∼ 500 K. The hysteresis is characterized by the coercivity field, Hc, decreasing between ∼100 and 75 Oe when T is increased from 5 to 510 K. The values of Hc are in reasonable agreement with the effect of the largest MnSb inclusions. The maximum of M (T), measured in the zero-field-cooled and the field-cooled conditions in a weak field of 500 Oe, is observed at T ∼ 510 K and is attributable to the Hopkinson effect.

Thermoelectric properties of Co4−xMnxSb12−ySny skutterudites

Mn/Sn-doped CoSb3 (Co4-xMnxSb12−ySny) skutterudites were synthesized by mechanical alloying, and their thermoelectric properties were examined. A single δ-phase was obtained successfully by post-annealing and hot pressing; however, MnSb phase was observed in Co2.5Mn1.5Sb12 and Co3MnSb11.2Sn0.8 specimens. Temperature dependence of the electrical conductivity suggests that the Mn/Sn-doped specimens are degenerate semiconductors. Every specimen had a positive Seebeck coefficient, and a Co3MnSb11.6Sn0.4 specimen exhibited the highest value. Mn doping caused a decrease in the Seebeck coefficient, but it could be enhanced by Mn/Sn double doping, possibly due to charge compensation. The thermal conductivity was desirably very low, and this originated from ionized impurity-phonon scattering. Thermoelectric properties were remarkably improved by Mn/Sn doping, and a maximum figure of merit, ZT = 0.54 was obtained at 723 K in the Co3MnSb11.6Sn0.4 specimen.

Magnetic and Electrical Behavior of MnTe 1− xSb x Alloys

The structure, specific heat, magnetic and electrical properties of MnTe 1- x Sb x ( x=0, 0.1, 0.15, 0.2 and 0.25) alloys have been investigated. The MnTe 1- x Sb x alloys crystallize in a hexagonal NiAs-type structure, and the impurity of MnSb phase appears when x≥0.15. The MnTe 0.9Sb 0.1 compound exhibits ferrimagnetic behavior with hysteresis loops even at 350 K, showing that the magnetic properties of MnTe compound are very sensitive to little compositional change. The ferromagnetism in the MnTe 1- x Sb x alloys with higher Sb contents may be attributed to the impurity of MnSb phase. Energy dispersive X-ray spectroscopy analysis on the MnTe 0.9Sb 0.1 compound indicates that Sb is very difficult to dope into the lattice of MnTe. So the anomaly of resistivity at 300 K of MnTe 0.9Sb 0.1 and the peak of specific heat around 304 K of all the alloys are thought to be related with the antiferromagnetic interactions of MnTe-based lattice.

Distribution of alloying elements and the corresponding structural evolution of Mn–Sb alloys in high magnetic field gradients

The distribution of alloying elements and the corresponding structural evolution of Mn–Sb alloys in magnetic field gradients were investigated in detail. It was found that a high magnetic field gradient could control the distribution of solute element in the alloys during the solidification process and therefore resulted in the coexistence of both primary MnSb and Sb phases or the aggregation of the primary MnSb with a continuous change in morphology. The positions where these primary phases located depended on the direction of field gradient. The control of the solute element distribution by a high magnetic field gradient was realized through the magnetic buoyancy force that could drive the migration of Mn element in the melt, originating from the difference in the magnetic susceptibility between Mn and Sb. The effectiveness of this control depends on the alloy composition, specimen dimension, cooling rate, and |BdB/dz| value.

Magnetic cluster developement in In1−x MnxSb semiconductor alloys

Abstract X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM) and magnetic measurements as a function of applied magnetic field and temperature for In1−x MnxSb (0.05≤x≤0.2) system are reported. Magnetic measurements performed at high and small magnetic field in ZFC and FC indicate the coexistence of ferromagnetic In1−x MnxSb solid solution and two types of magnetic cluster: ferromagnetic MnSb and ferrimagnetic Mn2Sb. XPS valence band and Mn 2p core level spectra have confirmed the presence of MnSb and Mn2Sb phases. TEM images show some manganese antimonide phase microinclusions with dimension between (30–40) nm.

Effects of high magnetic fields on solidified structures of Mn-90.4 wt% Sb hypoeutectic alloy

Mn-90.4 wt% Sb alloy specimens were solidified under both uniform magnetic field and magnetic field gradient conditions. The solidification behavior was examined to elucidate the effects of high magnetic fields on the solidified structure evolution of this hypoeutectic alloy. The macrostructures on the longitudinal section of the alloys were investigated by optical microscopy and x-ray diffraction (XRD). The volume fraction of primary MnSb phases and the interrod spacing of the eutectic were measured by metallographic analysis. It was found that the segregation of the primary MnSb particles at the certain regions of the specimens occurred under the influence of high magnetic field gradients. The MnSb phases obtained under magnetic fields were oriented with their (h0 l) planes along the direction of the magnetic field. Both the volume fraction of primary MnSb phases and the interrod spacing of the eutectic were decreased upon the application of the high magnetic fields.

MnSb/porous silicon hybrid structure prepared by physical vapor deposition

MnSb/porous silicon hybrid structure was prepared by physical vapor deposition technique. The structure and surface morphology of the MnSb films were analyzed by X-ray diffraction and scanning electron microscope, respectively. The magnetic hysteresis loops were obtained by an alternative gradient magnetometer. Based on the measurements, only MnSb phase was found and the surface morphology was rough and island-like. MnSb thin films show ferromagnetism at room temperature.

Temperature dependence of perpendicular magnetic anisotropy for c-plane-oriented MnSb sputtered films

The temperature dependence of magnetic anisotropy was investigated for c-plane-oriented MnSb sputtered films. The main results were as follows: (1) A MnSb phase with low Mn contents between 50.1 at. % and 50.8 at. % was formed in c-plane-oriented MnSb films. (2) It was clarified that the perpendicular magnetic anisotropy, which originated from uniaxial magnetocrystalline anisotropy of NiAs-type hexagonal structure, changed from a negative value of −3.99×106 erg/cm3 at room temperature to a positive value of 3.73×105 erg/cm3 at 300 °C. The perpendicular magnetic anisotropy crossed 0 erg/cm3 at about 270 °C. (3) The formation of the MnSb phase with Mn content of about 51.5 at. % was necessary to reduce the transition temperature, where the MnSb film changed its easy axis from the film plane to the film normal direction, to 150–200 °C.

NMR evidence for MnSb environments within epitaxial NiMnSb films grown on GaAs(0 0 1)

A thorough structural study has been performed on a series of MBE-grown NiMnSb/GaAs(0 0 1) films using 55Mn and 121(123)Sb nuclear magnetic resonance. In addition to a small amount (<4%) of classical point defects, the films reveal some twinning faults leading locally to formation of hexagonal MnSb. In case of stoichiometric NiMnSb, the amount of MnSb phase is estimated to be about 14% of a total sample volume. The excess of Sb increases the amount of MnSb environments, while in the Sb poor samples these inclusions practically disappear.

Molecular beam epitaxy of III–V diluted magnetic semiconductor (Ga,Mn)Sb

(Ga,Mn)Sb with a few percent order of Mn was grown by molecular beam epitaxy. Two growth temperature ranges were studied; one is normal growth temperature of GaSb (∼560°C) and the other is low temperature (250°C or 300°C). The properties of samples grown at these two growth temperatures were investigated by in situ reflection high-energy electron diffraction, atomic force microscopy, magnetization, and magnetotransport measurements. The results suggest the coexistence of two magnetic phases, (Ga,Mn)Sb and MnSb, for the samples grown at low temperature, whereas MnSb phase is dominant for the samples grown at high temperature.