Magnetic Properties Of Mn Research Articles

Synthesis, Dielectric and Magnetic Properties of Mn+2-Substituted Y-Type Hexagonal Ferrites: Prospects for Microwave Absorption Applications

Synthesis, Dielectric and Magnetic Properties of Mn+2-Substituted Y-Type Hexagonal Ferrites: Prospects for Microwave Absorption Applications

Structural and magnetic properties of Mn1.25Fe0.7P0.5Si0.5 alloys prepared by spark plasma sintering using raw materials milled with different lengths of time

Spark plasma sintering (SPS) is an effective method for synthesizing the Fe2P-type alloys due to its fast heating rate and short sintering time. Raw materials in the form of powder are sintered and pressed simultaneously in the preparation. Therefore, the particle size of the powder would have important influences on the structural and magnetic properties of the Fe2P-type alloys. In this work, the structure and magnetic properties of Mn1.25Fe0.7P0.5Si0.5 alloys prepared by SPS using raw materials milled with different lengths of time were investigated. We found that the particle size of the raw materials reduced mainly within milling time of 5 h and only slight difference existed when the milling time exceeded 5 h. Obvious secondary phase of (Mn,Fe)3Si was observed in the alloy prepared with milling time of 1 h. Other alloys prepared with milling time of 2 h, 5 h and 10 h showed similar magnetic properties. Giant isothermal entropy change values of 7.4 ∼ 9.6 J ⋅ kg−1 ⋅ K−1 for a magnetic field change of 1.5 T were obtained near room temperature for the alloys. The results demonstrate that a milling time longer than 2 h is required to obtain such magnetocaloric Mn-Fe-P-Si alloys with excellent magnetic properties using SPS method and the obtained alloys are promising candidates for magnetic refrigeration near room temperature.

Half-Metallic Ferromagnetism in TM-Doped GaN Nanosheet — A Potential Candidate for Spintronics Device Application

Density functional theory (DFT) analyses were carried out to study electronic structures and magnetic properties of Mn- and Cu-doped GaNNS. To investigate the influence of transition metal atoms (TM) on magnetic properties, we substituted Ga atoms with Mn and Cu atoms in different concentrations. Investigation shows that TM leads to electronic structural reconstruction which changes their properties in this way, and plays a significant role in spin polarization. Although the pure nanosheet is a nonmagnetic semiconductor, the doped atoms induce magnetism in the structure. The band gap changes monotonically depending on the concentration of TM atoms. The observed good half-metal ferromagnetism GaNNS:Mn, allows them to be a potential candidate for use in spintronics. The local magnetic moment calculated from Mulliken analyses for the Mn atom is approximately 4.05[Formula: see text][Formula: see text]B.

Studies of electrical and magnetic properties of Mn-, Zn- and Ti-substituted lithium ferrites

Studies of electrical and magnetic properties of Mn-, Zn- and Ti-substituted lithium ferrites

Defect induced ferromagnetism in Mn3Ga

Ni-substituted Mn3Ga displays a weak ferromagnetism embedded in an antiferromagnetic (AF) phase. Upon field cooling, the alloy exhibits exchange bias and an open hysteresis loop, signifying kinetic arrest at room temperature. For the first time, a kinetic arrest is seen in a compound due to the first order transition of an embedded defect phase. A systematic study of crystal structure, local structure, and magnetic properties of Mn 3−x Ni x Ga (x = 0, 0.25) alloys reveal the origin of ferromagnetism in Mn2.75Ni0.25Ga is due to the segregation of a Heusler-type environment around Ni in the cubic Mn3Ga matrix. Upon temper annealing at 400 ∘C, these local structural defects around the Ni phase separate into a modulated ferromagnetic (FM) Ni-Mn-Ga Heusler phase. A strong interaction between the AF host and the FM defect phase gives rise to exchange bias. The first-order transition of the defect phase seems to be responsible for the observed kinetic arrest in Mn2.75Ni0.25Ga.

An Influence of Fluorinated Alkyl Substituents on Structure and Magnetic Properties of Mn(II) Complexes with Pyrazolyl-Substituted Nitronyl Nitroxides

New complexes of manganese(II) hexafluoroacetylacetonate [Mn(hfac)2] with 2-(1-R-3-pyrazol-4-yl)-4,4,5,5-tetramethyl-2-imidazoline-3-oxide-1-oxyl (R = CHF2, CH2CH2F, CH2CHF2 or CH2CF3) were synthesised and characterised structurally and magnetically. All complexes were prepared under similar conditions. Nonetheless, their crystal structures were considerably different. Depending on the structure of fluorinated alkyl substituent R, the complexation reaction led to complexes of three types: chain-polymeric complexes with the head-to-head or head-to-tail motif and complexes of molecular structure. All complexes show strong antiferromagnetic behaviour in a high-temperature region (150–300 K) and weak ferro- or antiferromagnetic exchange interactions at low temperatures. The stronger antiferromagnetic exchange, −101.7 ± 1.5 or −136 ± 10 cm−1, −82.3 ± 1.3 cm−1 and −87.4 ± 1.3 cm−1, was attributed to the magnetic interaction in three- or two-spin clusters: {>N∸O–Mn2+–O∸N<} or {>N∸O–Mn2+}, respectively. The weaker antiferromagnetic interaction, −0.005, between three-spin clusters or ferromagnetic interactions, 0.18–0.81 cm−1, between two-spin clusters are realised through the pyrazole ring or intermolecular contacts.

Carrier-mediated ferromagnetism in Mn(II)-doped ZnTe thin films and their optical properties: A first-principles study

We have investigated the opto-electronic and magnetic properties of Mn(II)-doped ZnTe thin films by employing Density Functional Theory (DFT). In the absence of additional carriers, spin-up Mn-ta levels are fully occupied, leading to a super-exchange mechanism. The effect of additional p-type doping on the ferromagnetism is studied by considering the addition of hole carriers, Zn vacancies, and C co-doping, and we found that in all cases, coupling of hole carriers with the spin-up Mn-states causes the stability of the ferromagnetism in the Mn(II)-doped ZnTe thin films. We discovered through the optical study that Mn(II) doping at the Zn site widens ZnTe's bandgap and produces spin-forbidden d-d transition peaks on the low energy side of the bandgap. The p-type defects in Mn(II)-doped films produce absorption peaks in the infrared region and improve the absorption efficiency. In addition, the optical bandgap and spin-forbidden d-d transition of Mn(II) to different modes of spin-spin interactions were correlated, and we found a red shift of d-d intra-band transition peaks as well as an optical bandgap in the FM-coupled Mn(II) ions system and a blue shift in the AFM coupled ions system, supporting the experimental observations.

Synthesis, crystal structures, thermal and magnetic properties of Mn(NCS)2 coordination compounds with 3-cyanopyridine

The reaction of Mn(NCS)2 and 3-cyanopyridine in different solvents leads to the formation of pure Mn(NCS)2(3-cyanopyridine)4 (1), Mn(NCS)2(3-cyanopyridine)2(H2O)2-bis(3-cyanopyridine) solvate (2) and Mn(NCS)2(3-cyanopyridine)(H2O) (4). In further investigations single crystals of Mn(NCS)2(3-cyanopyridine)2(H2O)2 (3) were accidentally obtained, but this compound cannot be prepared pure. Compounds 1-3 consist of discrete complexes with octahedrally coordinated Mn cations, whereas in compound 4 the Mn cations are linked by single µ-1,3-bridging thiocyanate anions into chains, that are further connected into layers by the 3-cyanopyridine coligands. Thermogravimetric measurements reveal that upon heating compound 1 loses some of the 3-cyanopyridine ligands and transforms into [(Mn(NCS)2)3(3-cyanopyridine)4]n (5), which is isotypic to the corresponding Cd compound reported in the literature. In this structure, the Mn cations are linked by pairs of thiocyanate anions into chains that are further connected into layers by every second 3-cyanopyridine coligand. When compound 2 is heated, a transformation into the complex 1 is observed, that upon further heating transforms into 5. Magnetic measurements for compound 4 show that the Mn-NCS-Mn exchange is dominant and antiferromagnetic, and susceptibility dependence in the paramagnetic phase is well described by the Heisenberg spin chain model. Below 2.77 K, the Mn(II) spins in 4 are ordered with a weak ferromagnetic component due to the Dzyaloshinskii-Moriya interaction.

Study structural, surface morphological and magnetic properties of Mn(1-x) Znx Fe2O4 by solid state reaction method

The powder of Mn-Zn ferrite having the chemical formula Mn(1-x)ZnxFe2O4 where x varies from 0, 0.1, 0.2, 0.3, 0.4, and 0.5 were synthesized by solid state Reaction method. The X-Ray Diffraction studies confirm the formation of spinel cubic structure. The particle size was calculated by X-ray broadening studies. Also the structural parameters like Lattice Constant, X-ray density, bulk density (d), Porosity (P), ionic radius (Ra , Rb) and anion parameter or the oxygen positional parameter for all the samples. The micro structural features of the samples were obtained using a Scanning Electron Microscopy (SEM). The magnetic properties of Mn(1-x)ZnxFe2O4 ferrites were strongly affected by the Zn content. The saturation magnetization increased. It may be due to relatively high orbital contribution of Mn2+ ions to magnetic moment, which gives large induced anisotropy.

Computational modeling of the defect structure, hyperfine and magnetic properties of the Mn2+-doped magnetite of the composition MnxFe3-yO4 (y = ⅔ x)

The defect structure, hyperfine and magnetic properties of Mn2+-doped Fe3O4 of the composition MnxFe3-yO4(y=⅔x) are modeled using atomistic and DFT calculations. The atomistic simulations show the substitution of the Mn2+ ions for Fe3+ ones at the tetrahedral sites to be energetically favorable than their substitution at the octahedral sites. These Mn2+ impurities are charge-balanced by the occupation of either Mn2+ or Fe 3+ ions of interstitial tetrahedral sites. The method of GGA with on-site Coulomb interaction approximation for the exchange-correlation potential is used to calculate the electronic structure, hyperfine and magnetic moments of the structurally most preferred models. The results obtained show the model in which all the Mn2+ ions substitute for tetrahedral Fe 3+ ions with Fe3+ ions expelled to interstitial tetrahedral sites to be consistent with the observed experimental trends of the hyperfine and magnetic properties.

Computational insights into electronic, magnetic and optical properties of Mn(II)-doped ZnTe with and without vacancy defects

First principles calculations have been performed to investigate the optoelectronic and magnetic properties of Mn(II); ZnTe DMS with and without native defects using first principle calculations. Our results find that anti-ferromagnetic coupling dominates in the pure Mn(II)-doped ZnTe system due to super-exchange (SE) mechanism. The impact of p-type and n-type defects on magnetic coupling in Mn(II)-doped ZnTe were discussed and we found that p-type defect such as Zn vacancy defects play important role in stabilization of FM state due to the formation of bound magnetic polaron (BMP) while n-type defect such as Te vacancy defect does not affect the ground state of Mn(II); ZnTe. The magnetic coupling of Mn(II) spins in the absence and presence of Zn vacancy were explained on the basis of phenomenological band structure model. The optical absorption spectra of pure ZnTe and Mn(II); ZnTe with and without vacancies have been investigated and we found that single Mn(II)-doping in the lattice of ZnTe generates an absorption band at energy around 2.02 eV, which is assigned to intra-band d-d transitions of Mn(II) dopant. The band at energy around 0.44 eV in the absorption spectrum of Mn(II)-doped ZnTe with Zn-vacancy may be due to the acceptor states produced by Zn vacancy at Fermi level and band around 1.6 eV in the spectrum of Te vacancy defect system are related to the donor states produced by Te vacancy defect. Moreover, the correlation of magnetic coupling with intra-band d-d transition bands and fundamental bandgaps of ZnTe were also discussed and it was found that intra-band transition peak of Mn(II) ions and optical band gap of ZnTe are blue-shift in AFM coupled Mn(II) ions and are red-shift in FM coupled ions system. Our present findings highlight the worthwhile half-metallic properties of Mn(II)-doped ZnTe, which can be obtained via Zn vacancy defect engineering; this can find broad applications for the fabrication of optoelectronic and spintronic devices.

Synthesis conditions, crystal structure and magnetic properties of Mn–Tm–Se selenides

Single-phase compositions in the MnSe–TmSe quasi-binary section have been synthesized by the method of reactions in the solid phase. The crystal structure of polycrystalline powders has been studied in CuKα-radiation. It was found that the samples in the concentration range 0  x  0.7 have a cubic structure of the space group Fm m3 . An increase in the concentration of Tm cations in the Mn1–xTmxSe compositions leads to an increase in the unit cell parameter a from 0.547 nm for the Mn0.975Tm0.025Se compound to 0.566 nm for the Mn0.3Tm0.7Se composition. Thin layers of Mn1–xTmxSe solid solutions were synthesized by the flash method on optically transparent glass substrates. The film thicknesses are in the range of values from 0.8 to 3.2 µm. It has been established that Mn1–xTmxSe films also have the system NaCl, S.G.: Fm m3 . The composition of the Mn1–xTmxSe films corresponds to the chemical composition of the MnSe–TmSe charge powders. In the temperature range ~ 80–900 K, the va lues of the specific magnetization and magnetic susceptibility of the studied selenides were measured. The results obtained make it possible to determine the temperature regimes for the synthesis of new magnetic semiconductor substances, including those in the film state. The synthesized substances can be used in multifunctional microelectronic devices, as well as in the development of new materials capable of operating in wide temperature ranges and under the influence of external magnetic fields.

Effect of halogen substituents on the intermolecular interactions and magnetic properties of Mn(III) complexes

Six mononuclear Mn(III) complexes with hexadentate Schiff-base ligand, the products of the reaction between a N,N′-bis(3-aminopropyl)ethylenediamine or triethylenetetramine and 5-X-salicylaldehyde have been synthesized: the I− salts of complexes 1–3 exhibit a gradual SCO behavior, [Mn(5-Cl-sal-N-1,5,8,12)]I (1) shows a nearly complete SCO with T1/2 = 125 K, whereas [Mn(5-Br-sal-N-1,5,8,12)]I (2) and [Mn(5-I-sal-N-1,5,8,12)]I (3) show a gradual and incomplete SCO above room temperature. [Mn(5-F-sal-N-1,4,7,10)]I (4) predominantly remains HS state at all temperatures. [Mn(5-I-sal-N-1,5,8,12)]NO3 (5) and [Mn(5-F-sal-N-1,5,8,12)]NO3 (6) show an almost full conversion to the HS state and a more gradual SCO having the T1/2 value of 282 K for 5 and 159 K for 6, respectively.

Dependence of Structural, Morphological and Magnetic Properties of Manganese Ferrite on Ni-Mn Substitution.

This paper presents the influence of Mn2+ substitution by Ni2+ on the structural, morphological and magnetic properties of Mn1−xNixFe2O4@SiO2 (x = 0, 0.25, 0.50, 0.75, 1.00) nanocomposites (NCs) obtained by a modified sol-gel method. The Fourier transform infrared spectra confirm the formation of a SiO2 matrix and ferrite, while the X-ray diffraction patterns show the presence of poorly crystalline ferrite at low annealing temperatures and highly crystalline mixed cubic spinel ferrite accompanied by secondary phases at high annealing temperatures. The lattice parameters gradually decrease, while the crystallite size, volume, and X-ray density of Mn1−xNixFe2O4@SiO2 NCs increase with increasing Ni content and follow Vegard’s law. The saturation magnetization, remanent magnetization, squareness, magnetic moment per formula unit, and anisotropy constant increase, while the coercivity decreases with increasing Ni content. These parameters are larger for the samples with the same chemical formula, annealed at higher temperatures. The NCs with high Ni content show superparamagnetic-like behavior, while the NCs with high Mn content display paramagnetic behavior.

The effect of the annealing temperature on the microstructural, magnetic, and spin-dynamical properties of Mn–Mg–Cu–Zn ferrites

The effect of the annealing temperature on the structural and magnetic properties of Mn0.15Mg0.15Cu0.2Zn0.5Fe2O4 ferrite nanoparticles was investigated. All samples were carefully characterized using different techniques. The structural results showed that the ferrite was annealed at temperatures above 750 °C, and its structure was a combination of cubic spinel and hematite phases. Moreover, the XPS analysis showed that the valence state of the surface-metal ions and the surface-oxygen species played an important role in the structural and magnetic changes of this ferrite, so the increase in the hematite phase with the annealing temperature can be explained by the evaporation of the zinc content and the formation of a magnesium-metal state. The imaginary susceptibility as a function of the temperature of the samples shows a broad peak at high temperatures related to the blocking temperature of the interacting superparamagnetic nanoparticles and a second sharp peak related to the insulating spin-glass temperature.

Orbital competition of Mn3+ and V3+ ions in Mn1+x V2-x O4

The structural and magnetic properties of Mn1+x V2-x O4 (0 < x ⩽ 1) have been investigated by the heat capacity, magnetization, x-ray diffraction and neutron diffraction measurements, and a phase diagram of temperature versus composition was built up. For x ⩽ 0.3, a cubic-to-tetragonal (c > a) phase transition was observed. For x > 0.3, the system maintained the tetragonal lattice. Although the collinear and noncollinear magnetic transitions of V3+ ions were obtained in all compositions, the canting angles between the V3+ ions decreased with Mn3+-doping, and the ordering of the Mn3+ ions was only observed as x > 0.4. In order to study the dynamics of the ground state, the first principles simulation was applied to analyze not only the orbital effects of Mn2+, Mn3+, and V3+ ions, but also the related exchange energies.

New Mononuclear Mn(III) Complexes with Hydroxyl-Substituted Hexadentate Schiff Base Ligands

This paper reports the syntheses, crystal structures and magnetic properties of Mn(III) hexadentate Schiff base complexes [Mn(4-OH-sal-N-1,5,8,12)]NO3(1) and [Mn(4-OH-sal-N-1,5,8,12)]ClO4(2), where (4-OH-sal-N-1,5,8,12)2− (4,4′-((1E,13E)-2,6,9,13-tetraazatetradeca-1,13-diene-1,14-diyl)bis(3-methoxyphenol) is a new hydroxyl-substituted hexadentate Schiff base ligand. The introduction of the (4-OH-sal-N-1,5,8,12)2− ligand induces more hydrogen bonding interactions, in addition to promoting the formation of intermolecular interactions among the cations. However, the close-packing structures of both complexes lead to their stabilization in the high-spin state in the temperature range of 2−300 K.

Regulation mechanism of metal ions towards magnetic properties in Mn1−xZnxFe2O4

In this work, the microstructure, crystallographic parameters and magnetic properties of polycrystalline manganese–zinc (Mn–Zn) ferrites were investigated. Mn1−xZnxFe2O4 (0.11 ≤ x ≤ 0.14) were prepared by the solid-state reaction method at 1360 °C for 2 h in air atmosphere. Phase evolution and microstructure of Mn–Zn ferrites were investigated by XRD and SEM techniques. X-ray diffraction study confirmed the formation of spinel-structured Mn1−xZnxFe2O4. The magnetic properties were measured employing soft magnetic alternating current measuring instrument (MATS-3010SA). It was observed that as the zinc content (x) increases, the lattice constant remained stable, microstructure did not change significantly, the permeability of Mn–Zn ferrite was improved, and total loss and coercivity were reduced. Changes in crystal structure and magnetism were attributed to occupancy of non-magnetic Zn2+ and super-exchange interactions between the metal ions of sub-lattice A and B in the spinel structure. These results indicated that the magnetic properties of Mn1−xZnxFe2O4 ferrites were strongly affected by the Zn content (x). In a brief summary, Mn0.86Zn0.14Fe2O4 ferrite exhibited excellent magnetic properties with a low loss (Ps = 39.24 W/kg) and low coercivity (Hc = 39.16 A/m) measured at 200 mT and 10 kHz.

Effect of Cu2+ on structural, elastic and magnetic properties of nanostructured Mn–Zn ferrite prepared by a sol-gel auto-combustion method

The effect of Cu2+ substitution on the structural, elastic and magnetic properties of Mn0·50Zn0.50-xCuxFe2O4 (x = 0.00–0.25 and x changes at a step of 0.05) has been investigated. The compositions were made utilizing the Sol-Gel auto-ignition procedure and the X-ray diffraction (XRD) analysis confirmed the purity of the phase. Decreasing trends have been observed in the lattice constant, bulk density and Poisson's ratio but average grain size, theoretical density and porosity increases with the increasing concentration of Cu2+. Nano metric crystallite sizes have been estimated from FWHM of the X-ray diffraction peaks. Cation distribution in the present study was assessed by the XRD data. Site occupancy of cations helps to understand the variation in magnetic properties and also explains the change taking place in saturation induction, remanence induction and coercivity. The initial permeability increases with the increasing Cu2+ concentration up to x = 0.20 and above this x value it decreases. Observed variations of initial permeability have been clarified based on the increment of average grain size, which also has been conformed from optical micrographs. Saturation induction, coercivity, remanance, and squareness ratio have been considered as a component of Cu2+ content from theB−H loops of the compositions. Possible explanations for the perceived structural, elastic and magnetic behavior with Cu2+ substitutions are discussed.

Effects of oxygen vacancy on the magnetic properties of Mn(II)-doped anatase TiO2

We studied the magnetism of Mn(II)-doped anatase TiO2 (a-TiO2) with and without oxygen vacancy (VO) by Heyd-Scuseria-Ernzerhof hybrid functional method. Introduction of Mn(II) dopants causes the nonmagnetic a-TiO2 to have a magnetic moment, which is in direct proportion to the limited doped concentrations. The type of preferential magnetic coupling in Ti1-δMn(II)δO2 depends upon the Mn-Mn distance. Introduction of VO+ increases the local magnetic moment in Ti1-δMn(II)δO2, and the antiferromagnetism of the system is further enhanced. In contrast, the local magnetic moment of Ti1-δMn(II)δO2 with VO2+ does not change, but the ferromagnetic coupling becomes more stable.