Magnetic and Structural properties of $ MnV_ {2} O_ {4} $ (original) (raw)
Related papers
Magnetic and structural properties of Zn doped MnV2O4
2014
Magnetization, neutron diffraction and X-ray diffraction of Zn doped MnV 2 O 4 as a function of temperature have been measured and the critical exponents and magnetocaloric effect of this system have been estimated. It is observed, that with increase in Zn substitution the noncollinear orientation of Mn spins with the V spins decreases which effectively leads to the decrease of structural transition temperature more rapidly than Curie temperature. It has been shown that the obtained values of β, γ and δ from different methods match very well. These values do not belong to universal class and the values are in between the 3D Heisenberg model and mean field interaction model. The magnetization data follow the scaling equation and collapse into two branches indicating that the calculated critical exponents and critical temperature are unambiguous and intrinsic to the system. The observed double peaks in magneto-caloric curve of Mn 0.95 Zn 0.05 V 2 O 4 is due to the strong distortion of VO 6 octahedra.
Physical Chemistry Chemical Physics, 2016
We have investigated the crystal, electronic, and magnetic structures of Mn 5 O 8 by means of state-of-the-art density functional theory calculations and neutron powder diffraction (NPD) measurements. This compound stabilizes in the monoclinic structure with space group C2/m where the Mn ions are in the distorted octahedral and trigonal prismatic coordinations with oxygen atoms. The calculated structural parameters based on total energy calculations are found to be in excellent agreement with low temperature NPD measurements when we accounted for the correct magnetic structure and Coulomb correlation effect in the computation. Using fully relativistic generalized-gradient approximation with Hubbard U (GGA+U) we found that the magnetic ordering in Mn 5 O 8 is A-type antiferromagnetic and the direction of the easy axis is [1 0 0] in agreement with susceptibility and NPD measurements. However, the calculation without the inclusion of Hubbard U leads to ferrimagnetic half metal as a ground state contradictory to experimental findings, indicating the presence of a strong Coulomb correlation effect in this material. The GGA calculation without the Coulomb correction effect itself is sufficient to reproduce the experimentally observed magnetic moments in various Mn sites. We found that Mn in this material exhibits mixed valence behavior with 2+ and 4+ oxidation states reflecting different magnetic moments in the Mn sites. We explored the electronic band characteristics using total, site-, and orbital-projected density of states which emphasized the mixed-valent nature of Mn. A dominant Mn 3d character of the density of states at Fermi energy is the origin for the metallic behavior of Mn 5 O 8. The bond strength analysis based on the crystal orbital Hamiltonian population between constituents indicates strong anisotropy in the bonding behavior which results from the layered nature of its crystal structure. Our bonding analysis shows that there is a noticeable covalent bond between Mn 3d–O 2p states which stabilizes the observed low symmetric structure. Our experimental findings and theoretical predictions suggest that Mn 5 O 8 can be classified as a strongly correlated mixed valent antiferromagnetic metal.
Journal of the Physical Society of Japan, 2015
Element-specific magnetic structures, particularly orbital magnetic moments, of spinel-type MnV 2 O 4 were investigated using X-ray magnetic circular dichroism (XMCD). X-ray absorption and XMCD spectra clearly reveal that the Mn 2+ (d 5) and V 3+ (d 2) states are coupled antiferromagnetically. Analyses of XMCD spectra using magneto optical sum rules revealed that small but finite orbital magnetic moments remain in both V and Mn 3d states, which accounts for the antiferro-type orbital ordering in the V sites of MnV 2 O 4 with coexisting complex and real orbital states. Additionally, the Cr doping effect in MnV 2 O 4 was examined. The XMCD spectra of Cr 3+ (d 3) Ledges exhibited the substitution of Cr ions to the V sites ferromagnetically, with low conductivity through the suppression of the orbital ordering.
Magnetic behaviour of some Mn.III2.VI4 compounds and their alloys
Journal of Magnetism and Magnetic Materials, 1995
Measurement of the magnetic susceptibility χ as a function of temperature were made on polycrystalline samples from the alloy systems Cd1−zMnzGa2Se4, Zn1−zMnzGa2Se4 and Cd1−zMnzIn2Te4 which had been subjected to various heat treatments. The 1/χ versus T curves indicated that for the ZnSe alloys, for all values of z, samples slowly cooled to room temperature were antiferromagnetic showing ideal Curie-Weiss behaviour,
Structure and Magnetic Susceptibility of Mn11Ta4O21and Refinement of the Mn4Ta2O9Structure
Journal of Solid State Chemistry, 1998
The structure of Mn 11 Ta 4 O 21 has been determined and refined using the Rietveld method with combined CuK 1 X-ray and time-of-flight neutron powder data in space group P3 c1 to R F 2 ؍ 1.3% (neutron data) and R F 2 ؍ 7.8% (X-ray data). The unit cell is a ؍ 5.3776(2) A s , c ؍ 34.040(2) A > , V ؍ 852.5 A > 3 , and Z ؍ 2. The structure consists of a 14-layer hexagonal sequence of close packed oxygen atoms and an ordered distribution of metal atoms in octahedral coordination. It can be described as built up of corundum-type Mn 4 Ta 2 O 9 blocks, with six layers of octahedra, alternating with single MnO layers of octahedra. The structure is compared with that of corundum-related Mn 4 Ta 2 O 9 , with unit cell a ؍ 5.3306(2) A s , c ؍ 14.336(1) A s , V ؍ 352.8 A s 3 , and Z ؍ 2, which has been refined in space group P3 c1 to R F 2 ؍ 1.9%, using constant-wavelength (؍ 1.47 A >) neutron powder diffraction data. The magnetic susceptibility of Mn 11 Ta 4 O 21 exhibits a maximum at 23 K and a Curie-Weiss behavior at higher temperatures with a ؍ ؊240 K and eff ؍ 5.7 B per Mn atom.
Materials Sciences and Applications, 2015
In this work, Mn 2 O 3 nanoparticles (NPs) are prepared by co-precipitation technique. The synthesized sample is characterized by X-ray powder diffraction (XRD). The XRD spectrum reveals the cubic structure of Mn 2 O 3 NPs and the lattice parameter is calculated to be 9.4232 Å. Crystallite size (D) is estimated using Debye-Scherer's formula and is found to be 17.3 nm. A micrograph for the NPs is obtained using Transmission Electron Microscopy (TEM). The Mn 2 O 3 nanoparticles are viewed at 7500× magnification and their shape is spherical. D is also measured using TEM and it is 19.1 nm, which is very close to the one obtained from XRD. The elemental contents of the prepared samples are determined using particle induced X-ray emission (PIXE). In addition, the oxygencontent of the sample is obtained using non Rutherford backscattering spectroscopy (RBS) at 3 MeV proton beam. The sample shows high purity and the RBS technique is more accurate in determining the O-content. The presence of functional groups and the chemical bonding is confirmed by FTIR spectrum. The energy band gap (Eg) is calculated for the NPs using the UV-visible optical spectroscopy between 350 nm and 800 nm and found to be 1.24 eV. The sample shows high absorption in the visible range. The magnetization (VSM) is conducted to the sample and the saturation magnetization (M s) is calculated as 2.642 emu/g. The hysteresis loop shows antiferromagnetic behavior. The EPR analysis is performed at room temperature for the NPs. The g-factor is calculated from the spectrum and found to be 1.985, and the magnetic field shift occurs at B o = 350.5 mT. The intensity appeared to be high, which confirms the existence of Mn 2+ ions on the surface.
Static and dynamic properties of Mn2(OH)2(C4O4)
Physica B: Condensed Matter, 2006
The structure of Mn 2 (OH) 2 (C 4 O 4) consists of chains of hydroxide-bridged edge sharing triangles separated by the squarate anions. Here we present the variable temperature magnetic structure of a fully deuterated sample, along with new magnetic susceptibility data and inelastic neutron scattering measurements. The material becomes a 3-D antiferromagnet at 12 K, showing that the previous assignment of magnetic data was incorrect. The dynamic behaviour of this low-dimensional system is thought to be strongly influenced by short-range fluctuations-both above and below the transition to long-range order. This has been observed in the background contribution to the diffraction pattern and using inelastic neutron scattering. The initial results of neutron scattering are presented.
Structural, Optical and Room Temperature Magnetic Study of Mn2O3 Nanoparticles
Materials Sciences and Applications, 2015
In this work, Mn 2 O 3 nanoparticles (NPs) are prepared by co-precipitation technique. The synthesized sample is characterized by X-ray powder diffraction (XRD). The XRD spectrum reveals the cubic structure of Mn 2 O 3 NPs and the lattice parameter is calculated to be 9.4232 Å. Crystallite size (D) is estimated using Debye-Scherer's formula and is found to be 17.3 nm. A micrograph for the NPs is obtained using Transmission Electron Microscopy (TEM). The Mn 2 O 3 nanoparticles are viewed at 7500× magnification and their shape is spherical. D is also measured using TEM and it is 19.1 nm, which is very close to the one obtained from XRD. The elemental contents of the prepared samples are determined using particle induced X-ray emission (PIXE). In addition, the oxygencontent of the sample is obtained using non Rutherford backscattering spectroscopy (RBS) at 3 MeV proton beam. The sample shows high purity and the RBS technique is more accurate in determining the O-content. The presence of functional groups and the chemical bonding is confirmed by FTIR spectrum. The energy band gap (Eg) is calculated for the NPs using the UV-visible optical spectroscopy between 350 nm and 800 nm and found to be 1.24 eV. The sample shows high absorption in the visible range. The magnetization (VSM) is conducted to the sample and the saturation magnetization (M s) is calculated as 2.642 emu/g. The hysteresis loop shows antiferromagnetic behavior. The EPR analysis is performed at room temperature for the NPs. The g-factor is calculated from the spectrum and found to be 1.985, and the magnetic field shift occurs at B o = 350.5 mT. The intensity appeared to be high, which confirms the existence of Mn 2+ ions on the surface.
Crystal structures and magnetic properties of M2V2O7 (M=Co, Ni and Cu) compounds
Materials Chemistry and Physics, 2004
The magnetic properties of M 2 V 2 O 7 (M = Co, Ni and Cu) have been investigated between 4 and 300 K. The results emphasize the relationships between the structural and physical properties of the titled compounds. M 2 V 2 O 7 (M = Co, Ni) exhibit a dichromate structure. The Ni-compound is antiferromagnetic, but the Co-one is ferromagnetic. Their specific heats confirm the low dimensionality at high temperature, and the magnetic transition is probably due to 3d-1d transition. The two varieties of Cu 2 V 2 O 7 compounds are type thortveitite. ␣-Cu 2 V 2 O 7 is an orthorhombic and -Cu 2 V 2 O 7 is a monoclinic. The -Cu 2 V 2 O 7 is an antiferromagnetic compound while ␣-Cu 2 V 2 O 7 is appraised as a ferromagnetic or canted antiferromagnetic one.