Magnetic Moments Of Iron Ions Research Articles

Enhancing magnetism and magnetic separation of ultrafine chalcopyrite from talc through surface oxidation treatment

Magnetic separation has been proposed to greenly separate chalcopyrite and talc several decades ago, due to their extremely similar floatability of minerals. However, this approach was not achieved initially due to the inadequately magnetic induction of traditional magnetic separation, and fine particle size of chalcopyrite. Currently, the development of highly magnetic induction technology provides strong feasibility for this separation. In this work, we employed pulsating high-gradient magnetic separation (PHGMS) with highly magnetic induction (1.8T) to separate chalcopyrite and talc, and found that the PHGMS achieves a good separation of chalcopyrite from talc. But the chalcopyrite recovery decreased with the decrease of its particle size, and thus surface oxidation treatment was attempted to increase the magnetism and magnetic capture of ultrafine chalcopyrite. As a result, an increment of approximately 10 % was observed in the recovery of ultrafine chalcopyrite post-oxidation. As verified by the superconducting quantum interference device measurements, the oxidized ultrafine chalcopyrite exhibited a significant increase in the saturation magnetisation intensity, remanent magnetisation and coercivity values. Such magnetism enhancement is a result of the formation of paramagnetic Fe(III)–O–OH structures on the oxidized chalcopyrite surface, in terms of X-ray photoelectron spectroscopy and Mössbauer spectroscopy investigations. Furthermore, the density functional theory revealed that the formation of Fe(III)–O–OH structures caused a substantial increase in the magnetic moments of iron ions in antiferromagnetic chalcopyrite. These findings may extend the application of magnetic separation, and facilitate the flotation of ultrafine chalcopyrite from other minerals, at significantly reduced reagents use, and productive and environmental costs.

Role of Nd and Gd Dopants on Multiferroic Behavior of BiFeO-=SUB=-3-=/SUB=- --- A First-Principle Study

Electronic band structure, ferroelectric, and magnetic properties of multiferroic Bi1.xRExFeO3 (x=0, 0.16, 0.32, 0.5; RE=Nd and Gd) doped compounds have been investigated using TB-mBJ semi-local (Tran--Blaha modified Becke--Johnson) potential approximation method and WIEN2k code. As spin.orbit coupling (SOC) influences several properties of these materials, SOC corrections were also included in the present study. On the basis of varying band gap values, it has been concluded that the leakage current might have decreased with increasing dopant concentration. It has been concluded from the charge density studies that stereo chemically active 6S2 lone-pair electrons are present at Bi sites and they might be responsible for the displacements of Bi atoms from the centrosymmetric to the non-centrosymmetric structure position leading to the exhibition of ferroelectricity. It was also observed that magnetic moments of iron ions are not integral values probably due to hybridization of Fe electrons with neighboring O ions. To understand ferroelctric properties of these compounds, the real and imaginary parts of the dielectric functions were obtained at ambient conditions and were analyzed using TB-mBJ + SOCpotentials. Finally, it has been concluded that the results obtained in the present investigations may be useful in predicting the properties of bismuth ferrite for possible applications in industry. Keywords: multiferroics, TB-mBJ exchange potential, charge density, spin--orbit coupling (SOC),

Helical spin structure in the langasite family multiferroic Ba3TaFe3Si2O14, determined by Mössbauer spectroscopy

The magnetic structure of the Ba3TaFe3Si2O14 multiferroic of the langasite family has been studied using the Mössbauer spectroscopy and theoretical analysis within the full Hamiltonian of the combined hyperfine magnetic dipole and electric quadrupole interaction in the ground and excited states of 57Fe nuclei. The model is based on an antiferromagnetic triangular magnetic lattice with a 120° orientation of the iron spins in the ()-plane, which occurs below the Néel temperature . It was found that during translation along the c-axis, the magnetic moments of iron ions in triangular clusters rotate at an angle of . This angle remains constant with further translation, and a helical magnetic structure with a magnetic cell period of about 7c is formed. Excited states of magnetic moments arising due to a finite temperature are also considered. It has been established that the helical structure is well described by the proposed model in the entire temperature range T < TN.

Features of crystal structure and dual ferroic properties of [formula omitted] ([formula omitted] and [formula omitted]; x = 0.1–1.2)

The investigation of crystal and magnetic structures of BaFe12-xMexO19 (Me=In3+ and Ga3+; x = 0.1–1.2) solid solutions has been carried out by time-of-flight neutron diffraction method. It was determined the influence of diamagnetic In and Ga ions to unit cell volume of partially substituted barium ferrites. The electric field-induced polarization was observed in the BaFe11.9Me0.1O19 (Me = In and Ga) solid solutions at room temperature. The refinement of crystal structure of barium ferrites has been carried out in frameworks of two possible space group: centrosymmetric P63/mmc (No. 194) and non- centrosymmetric P63mc (No. 186) that allowed to reveal reasons of appearance of nonzero dipole electric moment. For description of magnetic structure of BaFe12-xMexO19 (Me = In and Ga; x = 0.1–1.2) solid solutions was used the Gorter’s model where magnetic moments of iron ions are oriented along the hexagonal axis that is the axis of easy magnetization.

Revisiting the magnetic structure and charge ordering in La1/3Sr2/3FeO3 by neutron powder diffraction and Mössbauer spectroscopy

The magnetic ordering of La$_{1/3}$Sr$_{2/3}$FeO$_3$ perovskite has been studied by neutron powder diffraction and $^{57}$Fe M\"ossbauer spectroscopy down to 2 K. From symmetry analysis, a chiral helical model and a collinear model are proposed to describe the magnetic structure. Both are commensurate, with propagation vector k = (0,0,1) in R-3c space group. In the former model, the magnetic moments of Fe adopt the magnetic space group P3$_{2}$21 and have helical and antiferromagnetic ordering propagating along the c axis. The model allows only one Fe site, with a magnetic moment of 3.46(2) $\mu_{\rm{B}}$ at 2 K. In the latter model, the magnetic moments of iron ions adopt the magnetic space group C2/c or C2'/c' and are aligned collinearly. The model allows the presence of two inequivalent Fe sites with magnetic moments of amplitude 3.26(3) $\mu_{\rm{B}}$ and 3.67(2) $\mu_{\rm{B}}$, respectively. The neutron diffraction pattern is equally well fitted by either model. The M\"ossbauer spectroscopy study suggests a single charge state Fe$^{3.66+}$ above the magnetic transition and a charge disproportionation into Fe$^{(3.66-\zeta)+}$ and Fe$^{(3.66+2\zeta)+}$ below the magnetic transition. The compatibility of the magnetic structure models with the M\"ossbauer spectroscopy results is discussed.

Electrical and Magnetic Properties of Hafnium Disulfide Intercalated with Iron Atoms

Simultaneous study of the dependences of the structural parameters, electrical, and magnetic properties of hafnium disulfide intercalated iron atoms in the dependence on the intercalate concentration and temperature has been performed for the first time. The temperature dependences of the electrical resistance are shown to exhibit the activation character with the activation energies characteristic of impurity conduction. The effective magnetic moments of iron ions in Fe x HfS2 is found to be significantly lesser than the values of free iron ions and to decrease as the iron content increases. The character of the temperature dependences of the effective magnetic moments and negative values of the paramagnetic Curie temperatures indicate possible interactions of the antiferromagnetic type between intercalated atoms. However, the dependences of the magnetization on field for Fe0.33HfS2 and Fe0.5HfS2 obtained at T = 2 K demonstrate the hysteresis phenomenon characteristic of the ferromagnetic state. The results are discussed assuming the existence of hybridization 3d electron states of intercalated iron atoms with the electronic states of HfS2 matrices and the competition of various exchange interaction.

Effect of Magnetic Pulse Processing on the Structure and Magnetic Properties of Ferrites

The effect a pulsed magnetic field has on the crystal structure and macroscopic magnetic parameters of hexagonal ferrites BaFe12O19 and SrFe12O19 are studied. It is shown that changes in the physical properties of ferrites are due to the ordering of cation vacancies on the boundaries of hexagonal and spinel blocks that minimize local distortion of the oxygen polyhedrons. Violation of the collinear ordering of the magnetic moments of iron ions in the nonequivalent positions of SrFe12O19 ferrite is observed, due to the selective localization of such vacancies (and thus violations of the magnetic relationships in Fe–O–Fe).

Электрические и магнитные свойства дисульфида гафния, интеркалированного атомами железа

AbstractSimultaneous study of the dependences of the structural parameters, electrical, and magnetic properties of hafnium disulfide intercalated iron atoms in the dependence on the intercalate concentration and temperature has been performed for the first time. The temperature dependences of the electrical resistance are shown to exhibit the activation character with the activation energies characteristic of impurity conduction. The effective magnetic moments of iron ions in Fe_ x HfS_2 is found to be significantly lesser than the values of free iron ions and to decrease as the iron content increases. The character of the temperature dependences of the effective magnetic moments and negative values of the paramagnetic Curie temperatures indicate possible interactions of the antiferromagnetic type between intercalated atoms. However, the dependences of the magnetization on field for Fe_0.33HfS_2 and Fe_0.5HfS_2 obtained at T = 2 K demonstrate the hysteresis phenomenon characteristic of the ferromagnetic state. The results are discussed assuming the existence of hybridization 3 d electron states of intercalated iron atoms with the electronic states of HfS_2 matrices and the competition of various exchange interaction.

Magnetic properties of BiFe0.93Mn0.07O3 powders obtained by ultrasonic spray pyrolysis

Samples of BiFe0.93Mn0.07O3 with different specific surface area were synthesized for the first time by ultrasonic spray pyrolysis. The resulting powders consist of porous particles of a spherical shape of medium size ~0.5 μm and have record values of residual magnetization and coercive force. It is found that the magnetic properties of the porous powder particles are determined by the distortion of the crystal lattice and the presence of uncompensated magnetic moments of iron ions on the surface.

Neutron diffraction study of the pressure and temperature dependence of the crystal and magnetic structures of Zn0.3Cu0.7Fe1.5Ga0.5O4 polycrystalline ferrite

The structural and magnetic properties of doped ferrite Zn0.3Cu0.7Fe1.5Ga0.5O4 have been studied by means of the neutron diffraction method at high pressures up to 4.7 GPa and in temperature range 300–425 K. By increasing the temperature and the pressure, a gradual suppression of the magnetic moments of iron ions in both A and B crystallographic sites was observed. This effect corresponds to a magnetic phase transition from the ferrimagnetic state to paramagnetic one. The lattice parameters, interatomic bond lengths and angles, magnetic moments of iron ions as functions of temperature and pressure were obtained. Upon compression, the magnetic ordering temperature of studied ferrite decreases with a large pressure coefficient dTc/dP = −19(1) K×GPa−1.

Magnetic Properties of Amorphous Fe&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;-R&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; (R=La, Gd and Tb) Thin Films Fabricated by Sputtering Method

Amorphous oxide thin films of Fe2O3-R2O3 (R = La, Gd and Tb) systems have been deposited on silica glass substrates by using a radio frequency sputtering method, and magnetic properties of the thin films have been examined. The Fe2O3-La2O3 thin films exhibit cusp-like maxima of dc magnetic susceptibility in their temperature dependences as well as magnetic aging and memory effects characteristic of typical spin glasses. For Fe2O3-Gd2O3 and Fe2O3-Tb2O3 systems, magnetic moments of iron ions take part in formation of a spin glass state, as indicated by the magnetic aging effects, while those of rare-earth ions remain to be in a paramagnetic state even at very low temperatures.

MÖSSBAUER STUDY OF57Fe IN LaNi1-xFexO3(x ≤ 0.2)

Mossbauer spectra of 57 Fe in LaNi 1-x Fe x O 3 (x = 0.05, 0.1, 0.2) were measured from 2K to room temperature. Isomer shift and the distribution of hyperfine magnetic fields were obtained as a function of temperature. The value of the isomer shift (≈0.34 mm/s) is the characteristic one for the Fe 3+ ions, while the value of the hyperfine field (≈400 kOe) extrapolated to OK is rather smaller than the expected value for the high spin state Fe3+ ions. In the spe~imen with x = 0.05, the magnetic moments of iron ions seem to be frozen in a random manner at low temperatures.

Structure and magnetic properties of Sm2(Fe1−xAlx)17Ny compounds

By means of x-ray phase analysis, it is shown that all the interstitial Sm2(Fe1−xAlx)17Ny nitrides and the parent compounds crystallize in Th2Zn17-type structure for x≤0.4. The lattice constants of the parent compounds increase linearly with Al concentration. The introduction of nitrogen leads to a further increase in lattice constants, but the amplitude of the increase decreases with increasing Al concentration. The introduction of nitrogen leads to an increase of Curie temperature Tc . The composition dependence of Tc of the parent compounds exhibits a maximum, whereas Tc of the nitride decreases monotonously with increasing Al concentration from 750 K for x=0 to 313 K for x=0.4. The mean magnetic moments of iron ions in both nitrides and parents decrease monotonously with increasing Al concentration.

Mössbauer Measurements in ZnY (Ba2Zn2Fe12O22) and Mn0.625–ZnY Ferrites

By means of the Mössbauer technique, the hyperfine magnetic fields and the electric quadrupole interactions in ZnY (Ba2Zn2Fe12O22) and Mn0.625–ZnY planar ferrites have been investigated. From the obtained spectra it is deduced that the Zn ions are randomly distributed over the tetrahedral sites of both S and T blocks and that Mn is substituting for Fe3+. The magnetic transition temperature for Mn0.625–ZnY turns out to be TC = (143±5)°C, not much different from that of ZnY, where TC = 135°±5°C. In these compounds the angle between the magnetic moment and the electric-field gradient differs from 90° showing the presence of angles between the magnetic moments of iron ions.