Magnetic Properties Of Mn Research Articles

Phase separated behavior in yttrium doped CaMnO3

The effect of electron doping on the structural, transport, and magnetic properties of Mn (IV)—rich Ca1−xYxMnO3 (x≤0.2) samples have been investigated using neutron diffraction, neutron depolarization, magnetization and resistivity techniques. The temperature dependence of resistivity follows the small polaron model and the activation energy exhibits a minimum for x=0.1 sample. A phase separated magnetic ground state consisting of ferromagnetic domains (∼7μm) embedded in G-type antiferromagnetic matrix is observed in the sample, x=0.1. The transition to the long-range magnetically ordered state in this sample is preceded by a Griffith’s phase. On lowering temperature below 300K a structural transition from orthorhombic structure (Pnma) to a monoclinic structure (P21/m) is observed in the case of x=0.2 sample. The ferromagnetic behavior in this case is suppressed and the antiferromagnetic ordering is described by coexisting C-type and G-type magnetic structures corresponding to the monoclinic and orthorhombic phases, respectively.

Influences of Ga content on the structure and magnetic properties of Mn2 -xNiGa1+x alloys

The structure magnetism and ordering transition of the ferromagnetic shape memory alloy Mn2 -xNiGa1+xhave been systematically studied in this paper. With increasing Ga content, the structure of the parent phase Mn2 -xNiGa1+x is transformed from Hg2CuTi-type to Cu2MnAl-type Heusler alloy gradually. Its lattice constant increases first and then decreases, reaching its maximum at x=0.3. The sample displays both the primary phase of Heusler and the Ni2In-type hexagonal phase in precipitate form when x lies in the range of 0.3-0.8. The Curie temperature of the primary phase of Heusler alloy Mn2 -xNiGa1+x reduces gradually from 590 K for Mn2NiGa to about 220 K for Ga2MnNi with the decrease of the exchange interaction between 3d electrons in the transition metals. However, the variation of Curie temperature of Ni2In-type hexagonal phase is gentle. The separation of Curie temperatures between the Ni2In-type hexagonal phase and the primary phase of Heusler occurs when x lies in the range from 0.6 to 0.8. Substitution of Mn by Ga has a significant influence on the coupling interaction among various atoms, leading to first increasing and then decreasing of the saturated magnetization of Mn2 -xNiGa1+x at low temperatures. That is, the saturated magnetization will rise for x0.4 and drops sharply for x0.4. Results of differential scanning calorimeter show that the melting temperature decreases gradually as x increases. Meanwhile, the transition temperature from parent phase (B2) to Heusler phase decreases first and increases later.

Synthesis, Crystal Structure and Magnetic Properties of Mn(II) Complexes with the Reduced Derivatives of Nitronyl Nitroxides

Synthesis, Crystal Structure and Magnetic Properties of Mn(II) Complexes with the Reduced Derivatives of Nitronyl Nitroxides

Electronic and Magnetic Properties Studies on Mn and Oxygen Vacancies Codoped Anatase TiO2

The electronic and magnetic properties of Mn and oxygen vacancies codoped anatase TiO2were investigated. The calculated results showed that the TiO2codoped with Mn and oxygen vacancies have a magnetic moment value of 3.415 μBper Ti31MnO63supercell. Furthermore, Ti31MnO63gets the lowest energy with a geometrical optimization where the Mn ions locate at the nearest-neighbor sites of the oxygen vacancy. And experimental results indicated the magnetism is associated with the defects of Mn ions and oxygen vacancies induced by the Mn doping, which is consistent with the calculation results.

Enhanced Magnetic Properties of Mn–Ni Codoped Cobalt Ferrite Nanoparticles Corroborated with Microstructural Analysis

Magnetic nanoparticles including ferrites are very potential candidates for its versatile application in the fields of engineering, bio medicine and electronics. Here we report the enhancement of magnetic properties of Mn-Ni co-doped cobalt ferrite nanoparticles which have been synthesized using coprecipitation technique. TEM study depicts the single phase nanocrystalline ferrite formation. Cation distribution between the tetrahedral and octahedral sites changes due to doping which is responsible for enhancement of magnetic properties. An exhaustive Rietveld analysis confirmed the rearrangement of the cations between the tetrahedral and octahedral sites. Also the results suggests strengthening of A-B and A-A interactions while weakening of B-B interaction for doped sample. ``Law of Approach'' technique is found to be useful and utilized to extract the detail of magnetic parameters like anisotropy constant, anisotropy field, coercivity.

Configurations and magnetic properties of Mn–B binary clusters

We investigate the structures and magnetic properties of boron-doped manganese clusters using first-principle density functional theory. We arrive at the lowest energy structures for clusters by simultaneously optimizing the cluster geometries, total spins, and relative orientations of individual atomic moments. For MnnB (n=2–12) clusters, the theoretical results indicate that the B atom prefers the surface site for all the lowest-energy structures except Mn10B cluster. The doped B atom enhances the stability of pure Mnn cluster. We also have studied the magnetic behavior of Mn–B clusters in the size range. Based on the analysis of the different magnetic behavior of boron-doped manganese clusters, we have further studied Mn9B2 and Mn8B3 clusters and it indicates that the doping of non-magnetism B element can induce all the Mn atoms align ferromagnetic coupling. Furthermore, a stable pearl necklace nanowire ([Mn8B3]n→∞) which retains the ferromagnetic ordering of all the manganese atoms has been predicted.

Synthesis and Magnetic Properties of Mn- Zn Ferrite Obtained by Decomposition of Precursor by Sunlight

Synthesis and Magnetic Properties of Mn- Zn Ferrite Obtained by Decomposition of Precursor by Sunlight

The Martensitic Transition and Magnetocaloric Effect of Mn-Poor MnCoGe Melt-Spun Ribbons

We investigated the martensitic transition and the magnetic properties of Mn1− x CoGe melt-spun ribbons. The as-prepared Mn1− x CoGe ribbons crystallize in austenite hexagonal phase with a textured structure. The postannealing process promotes the formation of the martensitic phase and homogenization of the alloy, resulting in a first-order magnetostructural transition in the annealed ribbons, and thus a giant magnetocaloric effect. The magnetic entropy change around the transition reaches 19 J/kgK for a magnetic field change of 0–5 T. Furthermore, it is found that the hysteresis loss around the magnetostructural transition is negligible in present annealed ribbons, which would facilitate the application of Mn1− x CoGe alloys.

Structural, optical and magnetic properties of Mn2+ doped ZnO-CdS composite nanopowder

Chemical precipitation method was used for the synthesis of Mn2+ doped ZnO-CdS composite nanopowder. The effect of Mn2+ doping was investigated on their structural, optical and magnetic properties. XRD pattern reveals the hexagonal phase of ZnO as well as CdS and the average crystallite size is found to be 18 nm. The morphological studies show non-uniformly distributed spherical like structures with little agglomeration. Crystal field and interelectronic repulsion parameters are evaluated from optical absorption study. EPR spectrum exhibits a well resolved sextet at g = 1.9924. By correlating optical and EPR studies, Mn2+ ions occupy octahedral sites in the host lattice which is also confirmed by PL analysis. From 1931 CIE chromaticity diagram, the prepared sample exhibits orange-red emission. IR spectrum confirms the existence of Zn-O and Cd-S vibrational modes. Room temperature ferromagnetism is observed in the prepared sample.

Structural, optical, and magnetic properties of Mn and Fe-doped Co3O4 nanoparticles

Mn and Fe-doped Co3O4 nanoparticles were prepared by a simple precipitation method. The synthesized particles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), UV-Vis absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and vibrating sample magnetometer (VSM) techniques. XRD analysis showed the cubic structure of Co3O4. SEM and TEM images confirmed the formation of interconnected nanoparticles. Mn and Fe-doped Co3O4 showed broad absorption in the visible region compared to undoped sample and the band gap values are red shifted. Five Raman active modes were observed from the Raman spectra. FTIR spectra confirmed the spinel structure of Co3O4 and the doping of Mn and Fe shifts the vibrational modes to lower wave number region. The magnetic measurements confirmed that Fe-doped Co3O4 shows a little ferromagnetic behavior compared to undoped and Mn-doped Co3O4, which could be related to the uncompensated surface spins and the finite size effects.

Nanoscale Clustering and Magnetic Properties of Mn x Fe3−x O4 Particles Prepared from Natural Magnetite

A series of Mn x Fe3−x O4 (0 ≤ x ≤ 1) nanoparticles was successfully synthesized via a simple coprecipitation method. The starting material was a natural magnetite purified from local iron sand. Crystallite nanoparticles were produced by drying without using a high calcination temperature. Rietveld analysis of the X-ray diffractometry (XRD) data for all samples demonstrated that the Mn ions partially substituted the Fe ions in the spinel cubic structure of the Fe3O4 to form Mn x Fe3−x O4 phases. We applied two lognormal spherical and single mass fractal models to the analysis of the small-angle neutron scattering (SANS) data and revealed that the primary Mn x Fe3−x O4 particles ranged in size from 1.5 to 3.8 nm and formed three-dimensional clusters as secondary structures. The samples displayed superparamagnetic behavior, having the saturation magnetization which was most likely influenced by the competing contribution from Mn, the sizes of the primary particles, and their clusters. Further analysis revealed that the zero-field-cooled and field-cooled curves of the Mn x Fe3−x O4 nanoclusters exhibited a superparamagnetic phenomenon with the lowest magnetic blocking temperature approximately 145 K.

Optical, electrochemical and thermal properties of Mn2+ doped CdS nanoparticles

Mn2+ doped (1–5 and 10 %) CdS nanoparticles have been synthesized by the chemical precipitation method using polyvinylpyrrolidone as a capping agent. The particle size, morphology and optical properties have been studied by X-ray powder diffraction, transmission electron microscopy, UV–Visible and photoluminescence spectroscopy. Powder diffraction data have confirmed that the crystallite size is around 2–5 nm. The band gap of the nanoparticles has been calculated using UV–Visible absorption spectra. An optimum concentration, Mn2+ (3 %) has been selected by optical study. The functional groups of the capping agent have been identified by fourier transform infrared spectroscopy study. The presence of dopant (Mn2+) has been confirmed by electron paramagnetic resonance spectroscopy. Thermal properties of CdS:Mn2+ have been analyzed using thermogravimetric–differential thermal analyser. The electrochemical properties of the undoped and doped samples have been studied by cyclic voltammetry for electrode applications. In addition, magnetic properties of Mn2+ doped CdS have been studied using a vibrating sample magnetometer.

Mn–Ge nanocluster formation vs. diluted magnetic semiconductuor formation

The possible fabrication of spintronic devices based on the Mn–Ge binary system supports extensive investigations on the magnetic properties of Mn–Ge structures. However, the global magnetic signal of a given sample is sometime complex due to the coexistence of several objects of unknown magnetic properties. We report the existence of ferromagnetic Mn–Ge nanoclusters (2–4 nm) containing only 4–6% Mn with a Curie temperature of ∼43.5 K, usually attributed to an 1.2% Mn-rich diluted magnetic semiconductuor.

Study of Half Metallicity in Mn, Fe and Mn/Fe Co-doped Cubic ZnS by First-principles

The electronic and magnetic properties of Mn, Fe and MnFe co-doped ZnS with zinc blende structure are studied by using first-principle's method. The ZnS doped with Mn and Fe is determined to be half-metallic, while MnFe co-doped ZnS is found to be semiconducting. Mn and Fe ions show long-range interactions that are mediated by magnetic moments induced in anions and cations of ZnS (host) semiconductor. These transition metal doped ZnS based half metallic ferromagnets seem to be good candidates for the future spintronic applications.

Electronic structure and magnetic properties of Mn1−xCrxSb alloys

The electronic structure and magnetic properties of Mn1−xCrxSb alloys were investigated for the full concentration range. The stability of the concentration-dependent magnetic structure of the alloys were analysed on the basis of spin–spiral calculations as well as using the Monte Carlo (MC) simulations based on the Heisenberg model with the exchange coupling parameters calculated from first-principles. A leading contribution to the canted magnetic structure in Mn1−xCrxSb is the competition of the direct Cr–Cr and Mn–Mn exchange interactions having opposite signs. Furthermore, a strong impact of long-distance RKKY-type interactions is demonstrated. MC simulations at finite temperature were used to obtain the magnetic phase diagram for Mn1−xCrxSb alloys, which is in reasonable agreement with the experimental data.

Dependence of magnetic properties on the growth temperature of Mn0.04Ge0.96 grown on Si (001)

The structural and magnetic properties of Mn 0.04 Ge 0.96 thin films grown on Si (001) substrates at different growth temperatures were investigated. The films were grown by sequential deposition of MnGe and Ge multilayers using molecular beam epitaxy . It was found that the magnetic ordering and Curie temperature could be controlled by adjusting the distance between the Mn ions in the Ge spacer layer depending on growth temperature. We found that the samples grown below 130 °C contained highly disordered ferromagnetic Mn rich domains. Both structural and magnetic characterizations revealed that Mn 5 Ge 3 precipitates were formed in Mn clusters free Ge matrix when the samples were grown at 150 °C. Both the Mn rich domains and Mn 5 Ge 3 precipitates showed out of the plane magnetic anisotropy and similar ESR line shapes. • We investigated the effects of growth temperature on spin systems in Mn 0.04 Ge 0.96 . • The degree of ferromagnetic ordering increases with temperature. • Ferromagnetism occurs due to interaction of Mn 2+ ions in Mn rich clusters. • ESR reveals that the formation of magnetic phases depends on growth temperature.

Low-Temperature Synthesis by Autocombustion and Investigation of Structural and Magnetic Properties of Mn0.5Cu0.5−xNixFe2O4 Nanocrystallites

Low-Temperature Synthesis by Autocombustion and Investigation of Structural and Magnetic Properties of Mn_0.5Cu_{0.5−<i>x</i>}Ni_<i>x</i>Fe₂O₄ Nanocrystallites

DFT + U Analysis of Structural, Electronic, and Magnetic Properties of Mn–As–Sb Ternary Systems

Electronic and magnetic investigations have been carried out on Mn–As–Sb ternary systems and their two end members, MnAs and MnSb, using ab initio techniques based on density functional theory plus U (DFT + U). Although the electronic structures of pure compounds have been extensively studied by first-principles calculations, there have been no reports of first-principles calculations of the evolution of the electronic structure with the composition. In order to get accurate results for these kinds of systems including Mn 3d electrons, we varied the U parameter from 0 to 10 eV for use in local density approximation (LDA) + U approach. The computed structural, electronic, and magnetic properties of MnX (X = As, Sb) are observed to display strong correlation with experimental data. In particular, the best agreement with the experimentis obtained within the LDA + U in which on-site Coulomb interaction parameter U eff for Mn is taken as 3.0 eV. Next, we have studied the energetic, electronic, and magnetic properties of alloys and we have also investigated the effects of compositional disorder in both hexagonal and orthorhombic structures. Several important properties of these materials were established. The improvement achieved with the ab initio LDA + U method and the agreement with the experimental spectra are discussed.

Electronic structure and magnetic properties of Mn and Fe impurities near the GaAs (110) surface

Combining density functional theory calculations and microscopic tight-binding models, we investigate theoretically the electronic and magnetic properties of individual substitutional transition-metal impurities (Mn and Fe) positioned in the vicinity of the (110) surface of GaAs. For the case of the ${[{\mathrm{Mn}}^{2+}]}^{0}$ plus acceptor-hole (h) complex, the results of a tight-binding model including explicitly the impurity $d$ electrons are in good agreement with approaches that treat the spin of the impurity as an effective classical vector. For the case of Fe, where both the neutral isoelectronic ${[{\mathrm{Fe}}^{3+}]}^{0}$ and the ionized ${[{\mathrm{Fe}}^{2+}]}^{\ensuremath{-}}$ states are relevant to address scanning tunneling microscopy (STM) experiments, the inclusion of $d$ orbitals is essential. We find that the in-gap electronic structure of Fe impurities is significantly modified by surface effects. For the neutral acceptor state ${[{\mathrm{Fe}}^{2+},h]}^{0}$, the magnetic-anisotropy dependence on the impurity sublayer resembles the case of ${[{\mathrm{Mn}}^{2+},h]}^{0}$. In contrast, for ${[{\mathrm{Fe}}^{3+}]}^{0}$ electronic configuration the magnetic anisotropy behaves differently and it is considerably smaller. For this state we predict that it is possible to manipulate the Fe moment, e.g., by an external magnetic field, with detectable consequences in the local density of states probed by STM.

Magnetism and magnetocaloric effect of Mn0.98Fe0.02CoGe

The crystallographic and magnetic properties of Mn0.98Fe0.02CoGe have been investigated by X‐ray diffraction, dc magnetization and neutron diffraction over the temperature range 20–450 K. The temperature dependence of the phase fractions of the orthorhombic and hexagonal phases is described well by a Gaussian distribution. The Mn0.98Fe0.02CoGe sample exhibits a first‐order magneto‐structural transition centred at TMS ∼ 297 K of FWHM ∼37 K with a magnetic entropy change of −ΔSM = 24(1) J kg−1 K−1 for ΔB = 0–5 T. Neutron diffraction indicates a ferromagnetic orthorhombic structure below TMS with only the Mn carrying magnetic moment (3.98(6) µB) at 20 K. The sample is paramagnetic in the hexagonal phase above TMS.