MnSb Films Research Articles

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

Structural characterization and magnetic response of poly(p-xylylene)\u2013MnSb and MnSb films deposited at cryogenic temperature

In this study, we employed several experimental techniques to investigate structure and magnetic properties of poly(p-xylylene)–MnSb composites synthesized by low-temperature vapor deposition polymerization technique and MnSb films deposited at various temperatures. The presence of MnSb nanocrystallites in the studied films was verified by the results of X-ray diffraction, electron microscopy and Raman spectroscopy studies. The obtained data revealed the formation of Sb-rich sublayer with well-oriented Sb grains near the susbtrate, which seems to act as a buffer for the consequent poly(p-xylylene)–MnSb or MnSb layer growth. Increasing the polymer content results in qualitative change of surface morphology of studied films. At high polymer content the hybrid nanocomposite with MnSb nanoparticles embedded into poly(p-xylylene) matrix is formed. All investigated samples demonstrated detectable ferromagnetic response at room temperature, while the parameters of this response revealed a complex correlation with nominal composition, presented crystal phases and surface morphology of studied films. Estimated values of the Curie temperature of the samples are close to that of bulk MnSb.

Effect of Growth Temperature and Postgrowth Annealing on Magnetic Properties of Mn1 + xSb Nanoparticles Embedded in GaSb Thin Films

Magnetic properties of two-phase granular semiconductor–ferromagnet GaSb–MnSb films obtained by pulsed laser deposition as a function of growth temperature and postgrowth annealing were stu-died.

Влияние температур роста и постростового отжига на магнитные свойства наночастиц Mn-=SUB=-1+x-=/SUB=-Sb, внедренных в тонкие пленки GaSb

The magnetic properties of two-phase granular semiconductor-ferromagnet GaSb–MnSb films obtained by pulsed laser deposition, depending on the temperature conditions of growth and postgrowth annealing, are investigated.

Growth and characterisation of MnSb(0 0 0 1)/InGaAs(1 1 1)A epitaxial films

MnSb layers have been grown on InxGa1-xAs(1 1 1) A virtual substrates using molecular beam epitaxy (MBE). The effects of both substrate temperature (Tsub) and Sb/Mn beam flux ratio (JSb/Mn) were investigated. The surface morphology, layer and interface structural quality, and magnetic properties have been studied for a 3 × 3 grid of Tsub and JSb/Mn values. Compared to known optimal MBE conditions for MnSb/GaAs(1 1 1) [Tsub = 415°C,JSb/Mn = 6.5], a lower substrate temperature is required for sharp interface formation when growing MnSb on In0.48Ga0.52As(1 1 1) A [Tsub = 350°C,JSb/Mn = 6.5]. At high flux ratio (JSb/Mn = 9.5) elemental Sb is readily incorporated into MnSb films. At higher substrate temperatures and lower flux ratios, (In,Ga) Sb inclusions in the MnSb are formed, as well as MnAs inclusions within the substrate. The Sb and (In,Ga) Sb inclusions are epitaxial, while MnAs inclusions are endotaxial, i.e. all have a crytallographic relationship to the substrate and epilayer. MBE optimisation towards different device structures is discussed along with results from a two-stage growth scheme.

Magnetotransport properties of InSb-MnSb nanostructured films

Hybrid nanostructured InSb - MnSb films were obtained by the pulsed laser deposition using the mechanical droplet separation. Films structure was characterized by different methods (electron diffraction, scanning electron microscopy, atomic and magnetic force microscopy). The negative magnetoresistance (nMR) takes place below 100 K. This temperature is several times more than the temperature at which the nMR occurs in homogenous In1-xMnxSb films. At low temperatures the spin-dependent scattering of the holes by the localized Mn2+ moments prevails. When the temperature rises, the low nMR is observed due to the weak spin-dependent scattering on magnetic inclusions.

Magnetism and Mn Clustering in (In,Mn)Sb Magnetic Semiconductors.

Previously, high-temperature ferromagnetism with a Curie temperature in excess of 400 K was reported in the magnetic semiconductor (In,Mn)Sb films grown by metal-organic vapor phase epitaxy (MOVPE). To determine the role of Mn distribution on its magnetic properties, the Mn 2p core-level X-ray photoelectron spectroscopy (XPS) of (In,Mn)Sb films was measured. For films grown on an InSb substrate, Mn composition is spatially inhomogeneous and its concentration increases with increasing deposition temperature. Spin-orbit splitting energy of the Mn 2p core-level was found to increase with increasing Mn concentration. From the dependence of the measured spin-orbit splitting energy on the Mn concentration, evidence of atomic-scale Mn cluster formation was observed. The measured magnetic moment per Mn atom decreases from 3.0 μB/Mn to 1.8 μB/Mn with increasing Mn concentration, which is attributed to atomic-scale clusters that are ferromagnetic or ferrimagnetic. This detailed investigation gives an insight into the Mn distribution, phase composition and origin of magnetism in MOVPE-grown (In,Mn)Sb magnetic thin films.

Martensitic phase transformations and magnetocaloric effect in Al co-sputtered Ni–Mn–Sb alloy thin films

Abstract We systematically investigated the influence of aluminium (Al) content on the martensitic transformations and magnetocaloric effect (MCE) in Ni–Mn–Sb ferromagnetic shape memory alloy (FSMA) thin films. The temperature-dependent magnetization (M–T) and resistance (R–T) results displayed a monotonic increase in martensitic transformation temperature (TM) with increasing Al content. From the isothermal magnetization (M–H) curves, a large magnetic entropy change (ΔSM) of 23 mJ/cm3 K was observed in N49.8Mn32.97Al4.43Sb12.8. A remarkable enhancement of MCE could be attributed to the significant change in the magnetization of Ni–Mn–Sb films with increasing Al content. Furthermore, a high refrigerant capacity (RC) was observed in Ni–Mn–Sb–Al thin films as compared to pure Ni–Mn–Sb. The substitution of Al for Mn in Ni–Mn–Sb thin films with field induced MCE are potential candidates for micro length scale magnetic refrigeration applications where low magnetic fields are desirable.

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.

Enhanced exchange bias in magnetron-sputtered Ni–Mn–Sb–Al ferromagnetic shape memory alloy thin films

In the present study, the influence of aluminium (Al) addition on the martensite-austenite phase transformation and exchange bias of Ni–Mn–Sb films have been investigated. Ni–Mn–Sb–Al films with different Al concentration (∼0–5.6%) were deposited by co-sputtering of Ni–Mn–Sb and Al targets. Experimental results revealed the decrease in martensitic transformation temperature with increasing Al content upto a certain extent (3.3%) beyond which martensitic transformation was suppressed. Paramagnetic to ferromagnetic transition temperature (TC) also decreased with increasing Al concentration. Ni50Mn36.3Sb10.4Al3.3 thin film showed significant improvement in exchange bias field as compared to pure Ni50.3Mn36.9Sb12.8 thin film. This enhancement in the exchange bias field HEB = 611 Oe at 10 K is attributed to the increase of AFM-FM interactions that result from the decrease of Mn–Mn distance due to the incorporation of Al atoms. This behaviour is an additional property of the FSMA thin films apart from various other multifunctional properties and therefore, is of technological importance for their applications in magnetic storage devices.

Preserving the half-metallicity at the interfaces of zinc-blende MnSb/GaSb heterojunction: A density functional theory study

Motivated by growing zinc-blende half-metallic MnSb films for the first time by molecular beam epitaxy experimentally Aldous et al., 2012, using the first-principles approach based on density functional theory, we investigate the electronic structure and half-metallicity at the (001) and (111) interfaces of zinc-blende MnSb with semiconductor GaSb heterojunction. Among the four studied configurations of MnSb/GaSb (001) and (111) interfaces, the (111)-Mn–Sb configuration is the most stable structure while the (001)-Sb–Ga configuration is the least favorable one. The MnSb slabs all stay to half-metallicity at the four interfacial configurations. Simultaneously, interfacial atoms Ga and Sb which from the nonmagnetic semiconductor GaSb slabs change to spin polarization, and show half-metallicity or nearly half-metallicity. Furthermore, the absolute values of magnetic moments of the interfacial atoms Mn and Sb in the half-metallic MnSb slabs decrease compared to the bulk values, while small moments are induced on the interfacial atoms Ga and Sb in the GaSb slabs.

Growth of magnetic eutectic GaSb-MnSb films by pulsed laser deposition

Eutectic GaSb + MnSb films ranging in thickness from 80 to 130 nm have been grown on sapphire substrates by pulsed laser deposition using mechanical droplet separation. The films were similar in composition to the ablation target, consisting of the eutectic GaSb-MnSb alloy. According to atomic force and electron microscopy data, the films were homogeneous, with p-type conductivity. Their electrical properties depended significantly on deposition conditions. The best films had a resistivity of 7 × 10−3 Ω cm, carrier concentration of 8.1 × 1019 cm−3, and carrier mobility of 102 cm2/(V s). Characteristically, the films had a negative magnetoresistance. Their magnetization curves showed saturation in a magnetic field of ∼1 × 10−1 T. According to the magnetic-field dependences, the coercive force in the films was within 3 × 10−2 T; that is, the films were soft magnets with a small domain size.

Heteroepitaxial Growth of Ferromagnetic MnSb(0001) Films on Ge/Si(111) Virtual Substrates

Molecular beam epitaxial growth of ferromagnetic MnSb(0001) has been achieved on high quality, fully relaxed Ge(111)/Si(111) virtual substrates grown by reduced pressure chemical vapor deposition. The epilayers were characterized using reflection high energy electron diffraction, synchrotron hard X-ray diffraction, X-ray photoemission spectroscopy, and magnetometry. The surface reconstructions, magnetic properties, crystalline quality, and strain relaxation behavior of the MnSb films are similar to those of MnSb grown on GaAs(111). In contrast to GaAs substrates, segregation of substrate atoms through the MnSb film does not occur, and alternative polymorphs of MnSb are absent.

Bulk and surface half-metallicity: Metastable zinc-blende TiSb

Motivated by the recent experimental fabrication of half-metallic MnSb and CrSb thin films with metastable zinc-blende structure [Aldous et al. Phys. Rev. B 85, 060403(R) (2012); Deng et al. J. Appl. Phys. 99, 093902 (2006)], we investigate the structural, electronic, and magnetic properties of TiSb in both ground-state NiAs and metastable zinc-blende phases by using the first-principles calculations. It is shown that the ground-state NiAs phase is metallic and nonmagnetic, but the metastable zinc-blende phase exhibits half-metallic ferromagnetism with a magnetic moment of 1.00 μB per formula unit. We also reveal that the half-metallicity in bulk ZB TiSb is lost at the Sb-terminated (001) surface due to the appearance of surface states within the gap of the minority-spin channel, but the Ti-terminated (001) surface retains the bulk half-metallicity, which makes ZB TiSb a promising candidate for the possible epitaxial growth of half-metallic thin films or multilayers on semiconductor substrates for spintronic applications.

Depth-dependent magnetism in epitaxial MnSb thin films: effects of surface passivation and cleaning

Depth-dependent magnetism in MnSb(0001) epitaxial films has been studied by combining experimental methods with different surface specificities: polarized neutron reflectivity, x-ray magnetic circular dichroism (XMCD), x-ray resonant magnetic scattering and spin-polarized low energy electron microscopy (SPLEEM). A native oxide ∼4.5 nm thick covers air-exposed samples which increases the film’s coercivity. HCl etching efficiently removes this oxide and in situ surface treatment of etched samples enables surface magnetic contrast to be observed in SPLEEM. A thin Sb capping layer prevents oxidation and preserves ferromagnetism throughout the MnSb film. The interpretation of Mn L3,2 edge XMCD data is discussed.

Distribution of Mn in ferromagnetic (In,Mn)Sb films grown on (0 0 1) GaAs using MBE

We characterize structural and magnetic properties of the dilute magnetic semiconductor (In,Mn)Sb grown on GaAs (001) by molecular beam epitaxy. The films have surface features consisting of dense orthogonally oriented strain-driven hillocks. In addition, triangularly shaped hillocks, presumed to be MnSb clusters, are observed with diameters in the range of 200nm. The density and size of these triangular hillocks depend strongly on the Mn content. X-ray scattering shows that the presence of Mn in the InSb films decreases the average lattice constant as well as the degree of relaxation of the (In,Mn)Sb films. The distribution of Mn is also investigated by cross-sectional transmission electron microscopy. Two regions are observed: a (In,Mn)Sb film with small defect density and MnSb clusters on the surface. Magnetization measurements indicate that both the (In,Mn)Sb alloy as well as the MnSb inclusions are ferromagnetic.

Structural and magnetic properties of Co–Mn–Sb thin films

Thin Co–Mn–Sb films of different compositions were investigated and utilized as electrodes in alumina based magnetic tunnel junctions with CoFe counterelectrode. The preparation conditions were optimized with respect to magnetic and structural properties. The Co–Mn–Sb/Al–O interface was analyzed by x-ray absorption spectroscopy and magnetic circular dichroism with particular focus on the element-specific magnetic moments. Co–Mn–Sb crystallizes in different complex cubic structures depending on its composition. The magnetic moments of Co and Mn are ferromagnetically coupled in all cases. A tunnel magnetoresistance ratio of up to 24% at 13 K was found and indicates that Co–Mn–Sb is not a ferromagnetic half-metal. These results are compared to recent works on the structure and predictions of the electronic properties.

Narrow‐gap ferromagnetic semiconductors (In,Mn)Sb on GaAs (001): growth and properties

AbstractNarrow‐gap (In,Mn)Sb layers, which offer prospects for infrared spin‐photonics, were grown on GaAs (001) substrates using a Riber Compact 21T MBE system and a Veeco valved cracker cell for Sb. Samples consisting 0.4 μm (In,Mn)Sb/GaAs with different Mn content in the range of 1% were examined in this study in respect of their structural, magnetotransport and magnetization properties. It is found that Mn decreases the lattice constant as well as the degree of relaxation of (In,Mn)Sb films. The hole concentration increases with increasing Mn concentration resulting increased acceptor concentration and decreased resistivity.The magnetoresistance is found to be sensitive to the Mn concentration. The temperature‐dependent resistivity data at lower than 30 K show an increased resistivity with decreasing temperature, suggesting the insulating behavior of the samples. In addition, magnetization measurements reveal distinct hysteresis loops, indicating the ferromagnetic properties. The measured saturation magnetization values of the films are found to be dependent on Mn concentration. The Curie temperature is estimated to be below 50 K. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Element-specific study of the temperature dependent magnetization of Co–Mn–Sb thin films

Magnetron sputtered thin Co–Mn–Sb films were investigated with respect to their element-specific magnetic properties. Stochiometric Co1Mn1Sb1 crystallized in the C1b structure has been predicted to be half-metallic and is therefore of interest for spintronic applications. It should show a characteristic antiferromagnetic coupling of the Mn and Co magnetic moments and a transition temperature TC of about 480 K. Although the observed transition temperature of our 20 nm thick Co32.4Mn33.7Sb33.8, Co37.7Mn34.1Sb28.2, and Co43.2Mn32.6Sb24.2 films is in quite good agreement with the expected value, we found a ferromagnetic coupling of the Mn and Co magnetic moments which indicates that the films do not crystallize in the C1b structure and are probably not fully spin polarized. The ratio of the Co and Mn moments does not change up to the transition temperature and the temperature dependence of the magnetic moments can be well described by the mean-field theory.

Inelastic scattering and spin polarization in dilute magnetic semiconductor (Ga,Mn)Sb

The point contact Andreev reflection technique has already been used to measure the spin polarization of some of the dilute magnetic semiconductors, such as narrow-band (In,Mn)Sb, as well as wider gap (Ga,Mn)As. While conventional Andreev reflection has been demonstrated in (In,Mn)Sb, quasiparticle density of states broadening has been observed in (Ga,Mn)As, possibly due to inelastic scattering effects. Here, we investigate the spin polarization, magnetic, and transport properties of epitaxially grown (Ga,Mn)Sb films with the Curie temperature of ∼10K. The spin polarization of 57±5% was measured. Spectrum broadening in (Ga,Mn)Sb has also been observed.