Mn Sn Research Articles

First-principles investigation of the structural and electronic properties of bulk full-Heusler alloy Mn2CoSn and its (0 0 1) surface

In this paper, the first-principles calculations have been performed to study the electronic and magnetic properties of the bulk and (001) surface of Mn2CoSn. The bulk Mn2CoSn Heusler alloy is found to be a half-metallic ferrimagnet with a total magnetic moment of 3.0μB per formula unit at the equilibrium lattice constant of 5.85Ǻ. The full-Heusler alloy displays a Slater-Pauling demeanor and the total magnetic moment (Mtot) with the total number of valence electrons (Ztot) complying the rule Mtot=(Ztot-24). Investigating the electronic density of states, we discover that the half-metallicity confirmed in the bulk Mn2CoSn is destroyed at both the Mn(2)Sn- and Mn(1)Co-terminated (001) surfaces. Moreover, we find the atomic magnetic moments at the Mn(2)Sn-terminated (001) surface are increased compared to those of the bulk Mn2CoSn, while they increase at the Mn(1)Co-terminated (001) surface. Interestingly, the spin state of Mn(1) atom is turned from low-spin state to high-spin state at the Mn(1)Co-terminated (001) surface, which makes Mn2CoSn full-Heusler alloy a promising candidate for spintronic applications.

Athermal nature of the martensitic transformation in Heusler alloy Ni–Mn–Sn

Martensitic transformations are generally classified into two groups, namely athermal and isothermal, according to their kinetics. In case of athermal transformations, the amount of the product phase only depends on temperature, and not on time. However, much debate rises about this issue due to unexpected experimental observations of isothermal effects in typically athermal transformations. Considering that the wide applications of Heusler Ni–Mn based materials are based on martensitic transformations, it is of importance to clarify the nature of their martensitic transformation. In this paper, we made an effort to study isothermal effects in a Ni–Mn–Sn alloy using differential scanning calorimetry (DSC). It is proposed that the martensitic transformation of Ni–Mn based materials is athermal in nature although a time-depending effect is observed through DSC interrupted measurements.

Microstructure and Magnetic Properties of Mn–Sn–N and Mn–Sn–Co–N Alloys

The microstructure and magnetic properties of Mn–Sn–N and Mn–Sn–Co–N alloys were investigated. All the samples showed low remanences, although high coercivity of 876 kA/m was observed in the Mn–Sn–Co–N alloys. The substitution of Co for Mn increased coercivity. The sample with high coercivity consisted of a fine two-phase microstructure of 0.5–2 µm in size.

Effect of Ti addition on the structural, mechanical and damping properties of magnetron sputtered Ni–Mn–Sn ferromagnetic shape memory alloy thin films

Titanium (Ti) co-sputtered Ni50.4Mn34.7Sn14.9 films deposited by magnetron sputtering onto Si(1 0 0) substrates at 823 K were investigated. X-ray diffraction profiles revealed the formation of highly (2 2 0)-oriented Ni–Mn–Sn–Ti austenite phase with significant decrease in grain size with increasing Ti power. Hardness (H), elastic modulus (Er), damping (tan δ), figure of merit (FOM) and coefficient of restitution (e) of the films were evaluated using nanoindentation tests. A significant improvement in the hardness (10.5 GPa) and toughness (0.040) was observed in the Ni51.0Mn28.2Sn11.0Ti9.7 nanocomposite film as compared with pure Ni50.4Mn34.7Sn14.9films. An impact model, which incorporates material behaviour, is presented that predicts the experimentally observed material quantities, including energy dissipation metrics such as the coefficient of restitution e with high accuracy. The highest damping factor (tan δ = 0.061), high FOM (0.79) with low coefficient of restitution (e = 0.28) quantifies excellent energy dissipation capacity in the Ni51.0Mn28.2Sn11.0Ti9.7 nanocomposite. Temperature dependence of magnetization (M–T) curves showed an increase in martensitic transformation temperatures with increasing Ti content. The Ni–Mn–Sn–Ti composite films exhibit ferromagnetic behaviour at room temperature.

Synthesis and molecular structure of mixed-metal stannylene derivatives of cyclopentadienyl(nitrosyl)(carbonyl) manganese

The metathesis of CpMn(CO)(NO)SnCl3 (I) and anionic carbonyls (ML−) Mn(CO)5−,Co(CO)4−,Cp′Mo(CO)3−,Cp′W(CO)3−,Cp″Mo(CO)3− provided trinuclear mixed-metal complexes of general formula CpMn(CO)(NO)SnCl2ML (VIII–XII; Cp = C5H5, Cp′ = C5H4CH3, Cp″ = C5H3(C4H9)2). Along with XII, the product of transmetallation Cp″Mo(CO)3SnCl3 (XIII) was separated. Interaction of I with Fe2(CO)82− gave the mixed-metal cluster Cp(CO)(NO)Mn–SnCl2–Fe(CO)4–SnCl2–MnCp(CO)(NO) (XIV) which contain the pentanuclear metal-chain. As determined by the single crystal XRD analysis, the Mn–Sn distance in CpMn(CO)(NO)Sn fragment is 0.2 Å shorter than the expected value based on the Mn/Sn sum of covalent radii (SCR). From the other hand, the shortening of Sn–ML distances is in an accord with the donor ability of an ML fragment in the row Co(CO)4 ∼ Mn(CO)5 < Fe(CO)4 < CpMn(CO)(NO < Cp′Mo(CO)3 < Cp′W(CO)3 < Cp″Mo(CO)3 owing to the additive back donation of the transition metal d-LEP to Sn vacant orbitals. The absence of substantial elongation of the Sn–Cl distances may result from the π-back donation of transition metal d-orbitals to tin d-orbitals.

Chemical Manipulation of Magnetic Ordering in Mn1–xSnxBi2Se4 Solid–Solutions

Several compositions of manganese-tin-bismuth selenide solid-solution series, Mn(1-x)Sn(x)Bi(2)Se(4) (x = 0, 0.3, 0.75), were synthesized by combining high purity elements in the desired ratio at moderate temperatures. X-ray single crystal studies of a Mn-rich composition (x = 0) and a Mn-poor phase (x = 0.75) at 100 and 300 K revealed that the compounds crystallize isostructurally in the monoclinic space group C2/m (no.12) and adopt the MnSb(2)Se(4) structure type. Direct current (DC) magnetic susceptibility measurements in the temperature range from 2 to 300 K indicated that the dominant magnetic ordering within the Mn(1-x)Sn(x)Bi(2)Se(4) solid-solutions below 50 K switches from antiferromagnetic (AFM) for MnBi(2)Se(4) (x = 0), to ferromagnetic (FM) for Mn(0.7)Sn(0.3)Bi(2)Se(4) (x = 0.3), and finally to paramagnetic (PM) for Mn(0.25)Sn(0.75)Bi(2)Se(4) (x = 0.75). We show that this striking variation in the nature of magnetic ordering within the Mn(1-x)Sn(x)Bi(2)Se(4) solid-solution series can be rationalized by taking into account: (1) changes in the distribution of magnetic centers within the structure arising from the Mn to Sn substitutions, (2) the contributions of spin-polarized free charge carriers resulting from the intermixing of Mn and Sn within the same crystallographic site, and (3) a possible long-range ordering of Mn and Sn atoms within individual {M}(n)Se(4n+2) single chain leading to quasi isolated {MnSe(6)} octahedra spaced by nonmagnetic {SnSe(6)} octahedra.

Metastability and inverse magnetocaloric effect in doped manganite (Nd0.25Sm0.25Sr0.5MnO3) and ferromagnetic shape memory alloy (Ni2Mn1.36Sn0.64): a comparison

The manganite Nd0.25Sm0.25Sr0.5MnO3 (NSSMO) shows a first-order metal to insulator transition on cooling, which is concomitant with a magnetic transition from the ferromagnetic to antiferromagnetic state. In some respect the sample shows a striking similarity with Ni–Mn–Sn based ferromagnetic shape memory alloys (FSMAs) undergoing a first-order magneto-structural transition, and efforts have been made to highlight the similarities and dissimilarities of the studied manganite with one such FSMA of composition Ni2Mn1.36Sn0.64. From our transport and magnetic investigations, the region of transition in the NSSMO is found to be highly metastable, with a clear indication of a magnetically arrested state which persists even when the sample is cooled down to the lowest temperature of measurement. Interestingly, the studied manganite shows an inverse magnetocaloric effect similar to the FSMA. However, a striking difference between the two compositions is evident in the low-temperature magneto-transport behavior: while a clear signature of tunneling magnetoresistance is present in NSSMO due to the coexisting metallic and insulating clusters of nanometer dimension, the studied FSMA do not show such behavior due to the absence of any insulating phase in the intermetallic alloy.

Magnetic properties and structural transformations in Ni–Co–Mn–Sn multifunctional alloys

A systematic study of the magnetic properties and both the temperature- and magnetic-field-induced structural transformations in the Ni50−xCoxMn39Sn11 (0⩽x⩽10) multifunctional alloys over a large temperature range from 500K down to 10K was performed. It is revealed that, with increasing x, the martensitic transformation temperatures first decrease slowly when 0⩽x⩽4 and then decrease rapidly when 5⩽x⩽8; no martensitic transformation was observed in the alloys with 9⩽x⩽10. The magnetic properties of these alloys are very sensitive to their chemical composition. The austenite in the alloys with 0⩽x⩽4 shows paramagnetic behavior and the martensite exhibits paramagnetic, superparamagnetic (SPM), and superspin glass (SSG) behaviors in different temperature ranges during cooling. In contrast, the austenite in the alloys with 5⩽x⩽8 is paramagnetic above its Curie temperature TC and ferromagnetic below TC, and the martensite shows SPM and SSG behaviors in different temperature ranges. The austenite in the alloys with 9⩽x⩽10, which remains stable down to 10K, shows paramagnetic and ferromagnetic behaviors above and below TC, respectively. The complete phase diagram for the Ni50−xCoxMn39Sn11 (0⩽x⩽10) alloy system, from high temperature down to 10K, is established. A significant magnetic-field-induced decrease of martensitic transformation temperatures and almost fully reversible magnetic-field-induced structural transformation are achieved across a broad temperature range in the alloys with 5⩽x⩽8. These results are important for understanding the composition and temperature-dependent functional properties, as well as their underlying mechanisms, in the Ni–(Co)–Mn–X (X=In, Sn, Sb) multifunctional alloys.

Martensitic transition of Mn-rich Pd–Mn–Sn alloy

A new magnetic shape memory alloy Pd2Mn1.46Sn0.54 has been synthesized. It was found that in the austenite phase Pd2Mn1.46Sn0.54 crystallizes in the L21 structure. It was confirmed from the low temperature X-ray diffraction measurements that the martensite phase of Pd2Mn1.46Sn0.56 has an orthorhombic four-layered structure. The magnetization versus temperature curve of Pd2Mn1.46Sn0.54 is very similar to those of the Ni–Mn–Z (Z=In, Sn and Sb) magnetic shape memory alloys; the paramagnetic–ferromagnetic transition appears in the austenite phase with decreasing temperature. With further decrease of temperature, the magnetization and permeability decrease abruptly at the martensitic transition temperature. The martensite phase remains ferromagnetic at low temperatures.

Electronic excitation induced phase transformation in FSMA thin film

The influence of 120 MeV Ag ion irradiation on the structural and magnetic properties of Ni–Mn–Sn ferromagnetic shape memory alloy thin film is investigated. X-ray diffraction data confirms the phase transformation from martensite to austenite phase at a fluence of 1 × 1013 ions/cm2, which is further supported by the change in surface morphology of the film with increasing fluence as evidenced by field emission scanning electron microscopy. Thermo-magnetic measurements reveal the increase in magnetization and decrease in phase transformation temperatures with increasing fluence. The maximum value of magnetization is ∼2.9 × 105 Amp/meter for the film irradiated at a fluence of 1 × 1013 ions/cm2. The results are explained on the basis of thermal spike model considering the core and halo regions of ion tracks in FSMA materials.

Energetic ion irradiation induced crystallization of Ni–Mn–Sn ferromagnetic shape memory alloy thin film

The ion irradiation induced crystallization of Ni–Mn–Sn ferromagnetic shape memory alloy (FSMA) thin film is investigated. Thin films of Ni–Mn–Sn FSMA synthesized by DC magnetron sputtering on Si substrate at 200 °C are irradiated by a beam of 120 MeV Ag ions at different fluence varying from 1 × 1012 to 6 × 1012 ions/cm2. X-ray diffraction pattern reveals that the pristine film grows in L21 cubic austenite phase with poor crystallinity and crystallinity of the film improves with increasing ion fluence, which is attributed to the strain relaxation by the energy deposited by incoming ions and promotes the grain growth. Grain growth is further confirmed by Atomic force microscopy. The temperature dependent magnetization measurements show improvement in the magnetic and shape memory properties of the films with increasing fluence, which is ascribed to the ordering of austenite phase. Nanoindentation measurements show that with increasing fluence of 120 MeV Ag ions, films exhibit a greater stiffness and smaller tendency towards plastic deformation.

Improved age-hardening behavior of Mg–Sn–Mn alloy by addition of Ag and Zn

The effect of 0.5at% Ag and its combination with 0.4at% Zn on the precipitation hardening behavior of Mg–1.5Sn–0.5Mn (at%) alloy have been investigated using hardness measurements and transmission electron microscopy (TEM). The results show that sole addition of Ag can remarkably improve the peak hardness from 58HV to 77HV after ageing at 200°C, which is attributed to the increased number density, the size and so the volume fraction of the Mg2Sn lath precipitates. A combination addition of Ag and Zn further improves the peak-hardness to 83HV and the time to peak hardness has been reduced from 120h to 100h. The joint addition of Ag and Zn both increases the number density and refines the Mg2Sn precipitates. Zn also promotes the Mg2Sn precipitates lying on the non-basal plane of matrix, as well as the blocky Mg54Ag17 phase which has an orientation relationship with α-Mg matrix as (001)ɛ′//(0001)α, [200]ɛ′//[−1−120]α, [0−20]ɛ′//[1−100]α. In the peak-aged Ag modified alloys, Ag atoms are segregated in the Mg2Sn precipitates. Nucleation, growth and coarsening of the Mg2Sn precipitates simultaneously occur as the ageing proceeds. The growth of Mg2Sn precipitates exhibits a significant anisotropic behavior. Addition of Ag can promote the precipitation process during the underage period and retarding the growth of Mg2Sn during the overage period, leading to a more thermal stable microstructure of the Ag and Ag+Zn modified alloys, from which only a small hardness decrease after 700h ageing is detected.

Exchange Bias in Ni-Mn-Sn Heusler Alloy Films

We report a relatively large exchange bias e ect observed for the rst time in Ni Mn Sn thin lms with di erent microstructure and composition: a Ni50Mn36Sn14 epitaxial lm (A), a Ni50Mn43Sn7 lm which is phase decomposed (B), and a NiMn/Ni50Mn25Sn25 bilayer (C). Despite the samples di er markedly in both microstructure and composition HEB does not substantially di ers at 5 K. Exchange bias decreases with increasing T approximately as HEB(T ) ∝ HEB(5 K)/T with HEB(5 K) of 180 Oe and 60 Oe for sample B and C, respectively and almost linearly for sample A with HEB(5 K) = 65 Oe. Blocking temperature where the exchange bias vanishes is 40, 50 and 80 K for sample A, C and B, respectively. The results suggest that the role of AFM/FM interfaces is not substantial in formation of exchange bias in Ni Mn Sn Heusler alloy lms and exchange bias is rather related to AFM/FM interactions in nanoscale.

Crystallography of Mg2Sn precipitates with two newly observed orientation relationships in an Mg–Sn–Mn alloy

Two new orientation relationships between β-Mg2Sn precipitates and α-Mg matrix have been observed by transmission electron microscopy. One is (1 1 0)β//(0 0 0 1)α, [0 0 1]β//[1 −1 0 0]α, and the other is (1 1 0)β//(0 0 0 1)α, [−1 1 −1]β//[1 −1 0 0]α. The precipitates with both orientation relationships exhibit a lath shaped morphology, with the long axis lying along [1 1 −2 0]α. The morphology is interpreted by a three-dimensional near coincidence sites model.

Characterization and interpretation of the morphology of a Mg2Sn precipitate with irrational facets in a Mg–Sn–Mn alloy

The crystallographic morphology of β-Mg2Sn precipitates at (near) Burgers orientation relationship (OR) with respect to the α-Mg matrix in a Mg–Sn–Mn alloy was investigated by transmission electron microscopy (TEM). Two irrational facets of the precipitates were found to be F1 ∼// (−1 1 0.74)β and F2 ∼// (−1 1 −3.1)β. The facets are interpreted according to interfacial structures. The presence of a singular dislocation structure in F1 requires a small rotation of 0.21° from the Burgers OR. The calculated morphology is consistent with the observations.

Phase transformation in Ni–Mn–Sn ferromagnetic shape memory alloy thin films induced by dense ionization

The effects of 200 MeV Au ions irradiation on the structural and magnetic properties of Ni–Mn–Sn ferromagnetic shape memory alloy (FSMA) thin films have been systematically investigated. In order to understand the role of initial microstructure and phase of the film with respect to high energy irradiation, the two types of Ni–Mn–Sn FSMA films having different phases at room temperature were irradiated, one in martensite phase (Ni58.9Mn28.0Sn13.1) and other in austenite phase (Ni50Mn35.6Sn14.4). Transmission electron microscope (TEM) and scanning electron microscope (SEM) images along with the diffraction patterns of X-rays and electrons confirm that martensite phase transforms to austenite phase at a fluence of 6×1012 ions/cm2 and a complete amorphization occurs at a fluence of 3×1013 ions/cm2, whereas ion irradiation has a minimal effect on the austenitic structure (Ni50Mn35.6Sn14.4). Thermo-magnetic measurements also support the above mentioned behaviour of Ni–Mn–Sn FSMA films with increasing fluence of 200 MeV Au ions. The results are explained on the basis of thermal spike model considering the core and halo regions of ion tracks in FSMA materials.

Intrinsic Optical Properties and Divergent Doping Effects of Manganese(II) on Luminescence for Tin(II) Phosphite Grown from a Deep-Eutectic Solvent

This is the first study on the ionothermal synthesis, intrinsic photoluminescence (PL), and dopant effects for tin(II) phosphite, a stereochemically active 5s(2) lone-pair-electron-containing compound, the fundamental properties of which have rarely been explored before. In a new deep-eutectic solvent, single-phased products of SnHPO(3) (1) and Sn(1-x)Mn(x)HPO(3) (2) have been achieved in high yield. The crystalline powder of 1 is nonenantiomorphic, with an intense second-harmonic generation comparable to that of potassium dihydrogen phosphate. Under UV excitation, it unexpectedly emits white PL, an important intrinsic property never discovered in tin(II) oxysalts. Electron paramagnetic resonance hyperfine splitting characteristic of manganese has been detected on 2 and a three-pulse electron-spin-echo envelope modulation technique implemented to locate its corresponding location in the inorganic host. On the basis of temperature-dependent PL and lifetime measurements, the incorporated Mn(2+) uncommonly acts as a sensitizer in enhancing white emission until extremely low temperatures, in which it would resume its normal role as an activator to give out characteristic orange light.

Temperature dependent magnetostrains in polycrystalline magnetic shape memory Heusler alloys

Abstract The transformation-induced strains with and without applied magnetic field and magnetostriction loops at different temperatures have been measured for polycrystalline ferromagnetic and metamagnetic shape memory Heusler alloys such as Ni Mn Ga, Ni Fe(Co) Ga and Ni Mn Sn, respectively. The results evidence a magnetic field oriented growth of martensitic variants during the martensitic transformation in Ni Mn Ga sample, whereas this effect is not evident in the other two alloys. In the Ni Mn Sn alloy, the isotropic volume magnetostriction dominates the anisotropic domain magnetostriction.

Atomic ordering effect in Ni50Mn37Sn13 magnetocaloric ribbons

► High-performance Ni–Mn–Sn magnetocaloric materials are produced. ► Ni 50 Mn 37 Sn 13 demonstrates great potential for magnetic refrigeration applications. ► A strong atomic order dependence is revealed in Ni 50 Mn 37 Sn 13 materials. High-performance Ni 50 Mn 37 Sn 13 magnetocaloric materials are produced using melt spinning technique in the present work and the atomic order dependence of phase transition behaviors and magnetic properties is established. The effective refrigeration capacity of the melt-spun ribbon annealed at 1273 K for 15 min reaches 95.27 J/kg for a magnetic field change of 18 kOe, demonstrating great potential for magnetic refrigeration applications near ambient temperature.

Magnetic and structural properties of Pd–Mn–Sn intermetallics compounds

Magnetic and structural properties of Heusler Pd0.5Mn0.5- x Sn x with x = 0.05, 0.10, 0.17, 0.20 and 0.25, have been studied by magnetisation and X-ray diffraction measurements at room and low temperatures. The crystal structure at room temperature is L21 cubic phase for x = 0.17, 0.20, 0.25 and B2 cubic phase for x = 0.10. Martensite structure 10M, was observed at room temperature for x = 0.05. X-ray measurements at low temperatures revealed a structural transformation from B2 to 14M for the x = 0.10 case. The lattice parameter of the L21 phase decreases linearly with the concentration, x. A ferromagnetic behaviour has been detected for L21 compounds, but the ferromagnetic exchange characteristic of each composition is of different strength. This gives rise to different Curie temperatures.