Phase Transition In Mn Research Articles

Cr-induced enhancement of structural stability in δ-MnO2 for aqueous Zn-ion batteries

δ-MnO2 was proposed as a promising cathode material for aqueous Zn-ion batteries. Nonetheless, its potential application has been impeded by its unstable crystal structure and sluggish reaction kinetics with Zn ions. Herein, we utilized Cr to modify δ-MnO2 by a simple hydrothermal method to develop cathode materials for aqueous Zn-ion batteries with better stability and electron transport properties. The introduction of Cr enhanced the specific capacity and cycling stability of δ-MnO2, in particular, the 3% Cr doped δ-MnO2 electrode exhibited a large specific capacity of 229.2 mAh·g−1 at 0.1 A·g−1 and an excellent capacitance retention of 86.0% after performing 300 cycles. The density functional theory (DFT) calculations indicate that the introduction of Cr decreases the band gap of MnO2 and enhances electron migration in the electrode material. Meanwhile, the introduction of Cr substantially improved the Zn ion adsorption and enhanced the binding energy of δ-MnO2, indicating that the addition of Cr promoted the interaction between the Cr doping δ-MnO2 (Cr-MnO2) electrode materials with Zn ions, while making the structure of the electrode materials more stable. As a result, this suppresses the Jahn-Teller distortion and reduces the solvation and phase transition of Mn.

Transport characterization of magnetic phase transition in Mn<sub>3</sub>Sn thin films

In recent years, topological antiferromagnetic material with hexagonal Kagome structure has attracted great research interest due to its unique properties. Although its net magnetic moment is close to zero, the topological antiferromagnet exhibits the strong magnetoelectric, the magneto-optical, and the magnetothermal effect, with a strength comparable to that of ferromagnetic material, which makes it highly valuable for various applications. After several years of extensive studies, it has been realized that most of the unique properties of topological antiferromagnet are actually closely related to its magnetic structure. However, it has been found that the magnetic structure of the material is highly sensitive to its chemical composition and growth condition. Therefore, it is crucial to develop a universal and simple method of measuring the magnetic structure and determining the magnetic phase transition of hexagonal Kagome topological antiferromagnetic material, which can severe as a good supplement for the current high-energy neutron diffraction approach that is not accessible for ordinary laboratories. In this study, we have successfully prepared high-quality (<inline-formula><tex-math id="M3">\begin{document}$ 11\bar{2}0 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231766_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231766_M3.png"/></alternatives></inline-formula>)-oriented hexagonal Kagome antiferromagnetic Mn<sub>3</sub>Sn thin films on (<inline-formula><tex-math id="M4">\begin{document}$1 \bar{1} 02$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231766_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231766_M4.png"/></alternatives></inline-formula>)-oriented Al<sub>2</sub>O<sub>3</sub> single crystal substrates by using the pulsed laser deposition method. After systematically measuring how the magnetic and transport properties of the Mn<sub>3</sub>Sn thin film change with temperature, it is found that its magnetization curve, Hall resistivity curve, and magnetoresistance curve exhibit certain anomalous features at some or all of its three magnetic phase transition temperatures. These features can serve as good evidences of magnetic phase transitions in this hexagonal Kagome antiferromagnetic Mn<sub>3</sub>Sn thin film, or even could be used to measure the temperatures of these magnetic phase transitions. Our work contributes to the further advancement of the application of hexagonal Kagome topological antiferromagnetic materials to spin electronic devices.

Understanding the formation of a cubic Mn0.6Fe0.4S solid-solution anode and its high performance for rechargeable lithium-ion batteries

A cubic Mn 0.6 Fe 0.4 S solid solution material has been synthesized using a scalable in situ sulfuration treatment of Prussian-blue analogs (PBAs), and its phase formation process and Li-storage mechanism were investigated. Increased treatment temperature and time encourage a phase transformation from hexagonal Fe 7 S 8 to cubic FeS 2 during the sulfuration process, which results in the formation of a solid solution between cubic FeS 2 and cubic MnS. The resulting Mn 0.6 Fe 0.4 S solid solution electrode exhibits high initial coulombic efficiency, excellent rate performance, and superior cycling stability (520 mA h g −1 after 1000 cycles at 1.0 A g –1 ). Ex-situ X-ray diffractometry and electro-kinetics tests show that the doping-induced structural phase transition in Mn 0.6 Fe 0.4 S solid solution creates a favorable electronic structure and ensures rapid charge transfer kinetics during the lithiation/delithiation process, simultaneously achieving high energy conversion efficiency and a long lifespan. • Cubic Mn 0.6 Fe 0.4 S solid solution as anode material is successfully synthesized. • The phase transition from α-MnS to metastable β-MnS could be induced in the charge process. • The improvement in electrochemical performance is attributed to the doping-induced structural phase transition in Mn0.6Fe0.4S.

Magnetostructural phase transitions and magnetocaloric effect in Mn(As,P) compounds and their composites

The magnetostructural phase transition in Mn(As,P) compounds was studied by a combination of X-ray diffraction on single crystals and by the magnetisation measurements. The mentioned transition is accompanied by anisotropic deformation of the crystal lattice, magnetisation hopping and heat evolving due to a large magnetocaloric effect (MCE). It is shown that this transition is a transformation from the hexagonal ferromagnetic to the orthorhombic paramagnetic phase at heating above the Curie temperature (TC). The values of the magnetic and lattice entropy changes at phase transition are obtained and the adiabatic temperature change is estimated in the frame of Clapeyron-Clausius relations. It is found that the MCE in the magnetic field 140 kOe reaches the value of 13.5 K. It is shown that a superparamagnetic structure (as a conglomerate of microscale areas) is formed above Curie temperature in zero magnetic field. On the other hand at the temperatures above the TC the ferromagnetic state is induced by magnetic fields exceeding the certain critical value Hcr while the above-mentioned superparamagnetic state is destroyed by the same magnetic fields. The magnetic properties of the bulk Mn(As,P) and the polymeric composite based on Mn(As,P) compound are compared.

Heterogeneous coherent interface thermodynamics and Wulff construction associated with the cubic-tetragonal-orthorhombic multi-step structural transition in Mn-Ni alloys

A variety of heterogeneous coherent interfaces is formed during the cubic (fcc)-tetragonal (fct)-orthorhombic (fco) multi-step structural phase transition in Mn- Ni antiferromagnetic shape memory alloy, which directly affects their shape memory effect, magnetic field-controlled memory effect and damping property. The thermodynamic properties of various types of interface in Mn-Ni alloys have been studied by using a universal chemical-structure model. The chemical energy and structural energy of fcc/fct, fct/fco and fcc/fco interfaces were calculated and compared, and it was found that the structural energy played a leading role in the total interfacial energy and the construction of Wulff shape. Besides the temperature, the interfacial orientation relationship has an important influence on the interfacial energy, which can be used to consider the singularity of coherent interface from the Wulff shapes. Based on this heterogeneous coherent interfacial energy model, the relationship between interfacial specific heat, interface entropy and interfacial enthalpy and temperature of fcc/fct, fct/fco and fcc/fco heterogeneous interfaces were calculated and compared from thermodynamic viewpoint. The effect of the softening modulus and the habit plane index on the interfacial energy was investigated.

Giant Magnetocaloric Effect in the Region of Magnetic Phase Transition in Mn (As,Sb) Compounds

The MCE in MnAs and doped Mn (As,Sb) compounds with low concentration of Sb has been studied by direct investigation. It was shown that for MnAs the maximum value of MCE is ΔT = 0.28 K on heating (at 308 K) and ΔT = 0.88 K on cooling (at T = 306 K) in magnetic filed 12.5 kOe. In doped Mn (As,Sb) compounds the temperature dependence of MCE is similar to MnAs. All investigated compounds demonstrate a strong temperature and field hysteresis of magnetic properties in magnetic field less than 40 kOe. It was established that a small concentration of Sb leads to decrease of MCE hysteresis and preserves the phase transition at room temperature region.

Mn(II) → Mn(III) oxidation kinetics and its effect on crystallization of nanodisperse platinum at 200–300°C and 1 kBar

In the Mn-H2O-Cl-Pt system, phase transitions in Mn(II)-Mn(III) solid compounds were experimentally shown to affect platinum solubility and platinum crystallization at 200–300°C (ptot = 1 kBar). Platinum dissolution rate curves feature a cooperative synergistic effect that results from overlapping of a concentration wave and a crystallization wave. The process is accompanied by crystallization of nonequilibrium intermediate phases, which are represented by flexivalent manganese hydroxides. Metallic platinum crystallizes as a result of a strong increase in platinum concentration in the solution during MnO oxidation to Mn3O4. With an electron microscope we observed precipitation of aggregates of isometric metallic platinum nanocrystals with cross sections of 60–550 nm on facets of hausmannite (Mn3O4) crystals. Walls of sealed platinum ampoules served as the platinum source during dissolution in the Mn-H2O-Cl system. As the run duration increased, Mn and manganese hydroxides were converted to hausmannite, which is stable at these p, T parameters. As a result, the platinum solubility dropped to equilibrium values (logmPt = −6.00 at T = 300°C), thereby inhibiting precipitation of crystalline platinum from solutions.

Study of 4 p Electronic States Related to Magnetic Phase Transition in Mn3MC (M=Zn and Ga) by X-ray Magnetic Circular Dichroism

To study the Zn and Ga 4 p electronic states in relation to the magnetic phase transition in Mn 3 M C ( M =Zn or Ga) perovskites, the temperature dependence of the X-ray absorption spectrum and X-ray magnetic circular dichroism was recorded at the Zn and Ga K -edges. As a result, it is found that the non-magnetic Zn and Ga atoms exhibit 4 p orbital polarization in the ferromagnetic state. For the second-order phase transition in Mn 3 ZnC, the canted-ferromagnetic component is separated from the ferromagnetic one, and the temperature behavior is compared with the case of the first-order transition in Mn 3 GaC. The Zn and Ga 4 p polarizations are strongly correlated with the Mn 4 p polarized states.

Pressure-Induced Phase Transition in Mn3O4as Investigated by Raman Spectroscopy

Pressure-Induced Phase Transition in Mn₃O₄as Investigated by Raman Spectroscopy

The characteristics of the diffuse phase transition in Mn doped Pb(Fe2/3W1/3)O3 relaxor ceramics

The characteristics of the diffuse phase transition of Pb(Fe2/3W1/3)O3 relaxor ceramics doped with different amounts of Mn are investigated. The freezing temperature Tf, obtained by fitting the ω,Tmax to the Vogel–Fulcher relationship, clearly changes with the Mn content. It increases as the Mn content increases, approaching the Tmax(1 MHz) value of the relaxor curve. A concomitant decrease in the frequency dispersion of Tmax is also observed. The freezing temperature also increases as the 1:1 order of Fe3+ and W6+on B sites increases by air annealing but decreases by oxygen annealing. It is suggested that the Mn ions, which are predominantly compensated by oxygen vacancies, form with them defect pairs and that these pairs can couple to the spontaneous polarization vectors, increasing the correlation between the dipole moments and originating the increase of the freezing temperature. It is further suggested that filling up the oxygen vacancies by oxygen annealing will decrease the defect pairs and cause the opposite effect.

EPR study of low temperature phase transitions in Mn 2+ doped K 2ZnCl 4

The EPR spectra of Mn 2+ doped K 2ZnCl 4 show an anomalously large broadening of the Zn site Mn 2+ lines between 152.5 K and 145 K, i.e. just above the transition to the low temperature commensurate phase of A1 a1 symmetry. The line broadening is related to a distribution of rotations of the ZnCl 4 tetrahedra and supports the existence of a second incommensurate phase in this temperature range as reported by Gesi.

Magnetic excitations around magnetic Brillouin zone centre in antiferromagnetic Mn(13.7%Ni) alloy

Our studies of the itinerant antiferromagnetic -Mn-based alloys are extended to investigate magnetic excitations in a Mn(13.7%Ni) alloy. The composition of the present sample being close to the part of the phase diagram where a number of structural phase transitions take place, the basic aim of this work is the search for the effect of these transitions on spin dynamics. This is the first study of the Mn - Ni alloy in the fct (c < a) phase. The parameters of the spin wave dispersion relation and their temperature dependence are determined and compared with those for Mn - Ni alloys in the fct (c > a) and fcc phases. We obtain the concentration dependence of the low-temperature parameters of the spin wave dispersion relation which differs essentially from that found for the Mn - Fe alloys. In particular the change of the spin wave parameters in the vicinity of the phase transitions in Mn - Ni alloys is remarkable.

Stability and the equation of state of alpha -manganese under ultrahigh pressure.

We have performed angle dispersive synchrotron-radiation x-ray powder-diffraction experiments on \ensuremath{\alpha}-Mn up to 190 GPa at room temperature by using a diamond-anvil cell and an imaging plate. We have obtained evidence for a structural phase transition in Mn above 165 GPa. A new diffraction peak appeared above 165 GPa, which can be most likely indexed to the 110 reflection of a body-centered-cubic structure. The volume reduction associated with the structural phase transition was estimated to be 2%. The bulk modulus and its pressure derivative of \ensuremath{\alpha}-Mn were determined as ${\mathit{B}}_{0}$=158 GPa and ${\mathit{B}}_{0}^{\ensuremath{'}}$=4.6, respectively. The pressure dependence of the bulk modulus indicates the decrease of the magnetic moments of Mn under pressure.

Successive magnetic phase transitions in Mn 3Pt

Successive magnetic phase transitions, from a paramagnetic to a collinear antiferromagntic (F) and then into a triangular (D) phase, observed in Mn3Pt are studied theoretically on the basis of the Heisenberg Hamiltonian by using the mean-field approximation. Exchange interactions between second-neighboring Mn atoms play an important role in the F-D phase transitions.

Effect of external pressure and chemical substitution on the phase transitions in MnAs

The evolution of the phase transitions in Mn 1− t T t As ( T = Ti, V, Cr, Fe, Co and Ni) with t at low substitution levels is correlated with the external pressure, temperature ( P, T) phase diagram of MnAs using the chemical pressure ( P ∗) concept. The study is based on data for transition temperatures and unit cell dimensions at atmospheric pressure and P, T phase diagrams of Mn 1− t T t ,As with different T and t. Chemical pressure coefficients (ranging between ϵ = −52 ± 2 kbar for T = Ti and ϵ = 133 ± 12 kbar for T = Fe, assuming P ∗ = ϵt) are estimated from the location of the boundary of the essentially pressure driven NiAs, F to MnP, P or MnP, H a type transition in the individual P, T phase diagrams. Different features of the chemical pressure concept are examined, such as the relation P ∗ = ϵt and its break-down above a certain substitution level, the correlation between unit cell volumes and compressibility, and the non-hydrostatic character of P ∗ for these non-cubic phases.

Effects of Compression and Magnetic Dilution on the First and Second Order Phase Transitions in Mn(HCOO)2·2H2O

Effects of compression and magnetic dilution on the first and second order phase transitions have been examined with Mn(HCOO) 2 ·2H 2 O, which exhibits both of the spin axis reorientation at T R =1.70 K and the antiferromagnetic transition at T N = 3.69 K. The application of hydrostatic pressure ( p ) makes a clear shift of T N ( p ) (d T N ( p )/d p = +0.022 T N ( p 0 ) K·kbar -1 ; p 0 ≃0 kbar) preserving a sharp heat capacity peak. However, the transition at T R ( p 0 ) = 1.70 K becomes quite obscure in the pressure with a broadening of the heat capacity peak around T R ( p )(d T R ( p )/d p = +0.078 T R ( p 0 ) K·kbar -1 ). These phenomena are compared with the phase transitions in the magnetically diluted system with Zn 2+ ions.

EPR Studies of a structural phase transition in Mn 2+-doped zinc fluotitanate hexahydrate

Electron paramagnetic resonance studies of Mn2+ in zinc fluotitanate hexahydrate (ZnTiF6·6H2O) have been made between 77 and 300 K, in the X-band frequency range. At 173±2 K a structural phase transition was observed. The axial symmetry at room temperature with a single magnetic site was destroyed in the low-temperature phase, where two crystallographically inequivalent sites rotated by 8° from the axis could be identified, with their symmetry axis retained along the room-temperature c axis. The important features associated with this phase transition are reported along with the room-temperature data.

Magnetic phase transition of Mn 1.88Cr 0.12Sb

The nature of the first order phase transition in Mn 1.88Cr 0.12Sb crystal is discussed. According to the magnetic susceptibility χ ⊥ and the specific heat measurements, there are two phase transitions, at 280 K and 315 K, respectively. They correspond to the vanishing of the “magnetic soft modes” for FIM and AF phases [4]. No change of the energy level positions was detected using the ESCA method.

A second-order phase transition in Mn(CO)5Br

Raman spectra of Mn(CO)5Br are reported at hydrostatic pressures of up to 50 kbar. Existence of a phase change is shown by changes of slope in frequency/pressure plots. The phase transition is a second-order transition. (AIP)

The model of metamagnetic phase transition in Mn3GaC

AbstractA new model of metamagnetic phase transition with temperature in Mn3GaC is proposed. The magnetoelastic Hamiltonian takes into account two independent strains (trigonal and isotropic ones) as functions of temperature, calculated similarly to the microscopic theory of magnetostriction. Necessary conditions for the transition are established within the molecular field approximation and the fit with experiment is discussed.