Stable Magnetic Phase Research Articles

Theoretical investigation of structural, magnetic and elastic properties of half Heusler LiCrZ (Z = P, As, Bi, Sb) alloys

In this study, physical properties of half Heusler (HH) alloys LiCrZ (Z = P, As, Bi, Sb) are explored using Wien2k package. All these alloys are found to be the most stable with Type-1 configuration. Furthermore, ferro-magnetic (FM), anti-ferromagnetic (AFM) and non-magnetic (NM) calculations are performed to obtain the most stable magnetic phase using Type-1 configuration and all compounds are found stable in FM phase. The calculated formation energy has also predicted that these alloys are stable. The LiCrBi and LiCrSb alloys showed 100% spin polarization and half metallic character. The calculated magnetic moment is 4 μB and band gap for LiCrBi and LiCrSb is 1.8 eV. The spin polarized density of states (DOS) have also been calculated and discussed. The effect of pressure on band gap has also been investigated. The increase in band gap and decrease in lattice constant with the increase of applied pressure have been observed and explained in detail. In order to check the mechanical stability, elastic constants are constants are calculated and all compounds are ductile. The predicted results of HH alloys will be useful for spintronics applications.

First-principles study of BiFeO3and BaTiO3in tetragonal structure

Structural, electronic, magnetic and mechanical properties of the perovskites BiFeO3(BFO) and BaTiO3(BTO) are investigated using density functional theory (DFT). Structural and mechanical parameters are calculated using generalized gradient approximation (GGA) and the results consistent with the available literature. The stable magnetic phases are achieved by optimizing total energies versus volumes of the cells in different magnetic configurations such as nonmagnetic (NM), ferromagnetic (FM) and antiferromagnetic (AFM). BTO is found to be NM while BFO favors G-type AFM (G-AFM) phase. The electronic properties are investigated using GGA, GGA with Hubbard potential (GGA[Formula: see text]+[Formula: see text]U) and modified Becke–Johnson (GGA-mBJ) exchange–correlation functionals. BFO is found to be a direct bandgap semiconductor having gap energy value 3.0 eV whereas BTO is an indirect semiconductor with bandgap energy 2.9 eV. Spin–orbit coupling effect is dominant in BFO due to the larger size of A-site cation. The electrical polarization shows that both the compounds are ferroelectric materials with significant spontaneous polarization of 144.1 [Formula: see text]C/cm2and 27.9 [Formula: see text]C/cm2for BFO and BTO respectively.

Magnetic orders and electronic behaviours of new chalcogenides Cu3MnCh4 (Ch = S, Se and Te): An ab initio study

ABSTRACTThe ternary copper-based chalcogenides Cu3MnCh4 (Ch = S, Se and Te), which have simple cubic (SC) crystal structure and conform to space group with 215 space number, have been investigated by spin-polarised Generalised Gradient Approximation (GGA) in the framework of Density Functional Theory (DFT). First, all systems have been considered in ferromagnetic (FM) and three different type antiferromagnetic (AFM) orders which are A-type (A-AFM), G-type (G-AFM) and C-type (C-AFM) to investigate most stable magnetic phase for each system. The energetically favoured magnetic phase is A-type AFM for Cu3MnS4 and Cu3MnSe4 compounds, while Cu3MnTe4 compound has FM ground state. The electronic band structures of these systems have been investigated, after the well-optimised structural parameters in their stable magnetic phase have been obtained. The calculated spin-polarised electronic band structure of FM Cu3MnTe4 compound exhibits half-metallic behaviour with a band gap in minority spin channel (Eg = 0.99 eV) while metallic band structure is observed for majority spin. The calculated electronic band structures in A-type AFM phase for Cu3MnS4 and Cu3MnSe4 systems show that Cu3MnS4 compound has semiconducting behaviour with a small band gap (Eg = 0.21 eV) whereas Cu3MnSe4 compound has metallic character. The calculated negative formation enthalpies indicate the thermodynamic stability and structural synthesisability of these compounds.

Integration of stable isotope labeling derivatization and magnetic dispersive solid phase extraction for measurement of neurosteroids by in vivo microdialysis and UHPLC-MS/MS

In this work, a novel strategy of stable isotope labeling derivatization (SILD) combined with magnetic dispersive solid-phase extraction (MDSPE), has been proposed for simultaneous monitoring of neurosteroids changes linked to Parkinson's disease (PD) by in vivo microdialysis. The developed method was based on ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) detection using multiple-reaction monitoring (MRM) mode. In this study, a new pair of stable isotope labeling reagents d0-/d3-3-N-methyl-2′-carboxyl Rhodamine 6G (d0-/d3-MCR6G), were designed and synthesized for derivatizing neurosteroids in rat blood microdialysates and neurosteroid standards, respectively. d3-MCR6G labeled neurosteroids standards were used as internal standard for the following pretreatment and UHPLC-MS/MS quantification to minimize the deviations caused by complex matrix and ion suppression effects in mass spectrometry analysis. Under the optimized derivatization and extraction conditions, good linearities of eight neurosteroids were obtained with correlation coefficients R2 values > 0.98. The limits of detection (LODs) and quantitation (LOQs) ranged from 0.06 to 0.12 pg/mL and 0.30–0.40 pg/mL, respectively. Taken together, the established method exhibited high sensitivity and selectivity, excellent accuracy, convenience and high efficiency. It was applied for the simultaneous and dynamic measurement of multiple neurosteroids in normal and PD rat blood microdialysates. This method would be expected to be potentially useful for the monitoring and drug treatment of PD and related neurological disorders in the future.

Magnetic ground state and pressure effect study on elasticity, electronic and magnetic properties of KUO3: DFT+U, GLLB-SC, mBJ and QTAIM investigations

Motivated by the lack of information on several physical properties of KUO3, we have undertaken a complementary and comparative study to the work already achieved on this compound. Magnetic ground state and the effect of hydrostatic pressure on elasticity, electronic and magnetic properties of KUO3 were studied using FP-(L)APW + lo method. The most stable magnetic phase of KUO3 has been found to be G-Type antiferromagnetic order, consistent with the experimental results. The study of the elasticity has shown that KUO3 maintains its mechanical stability under any hydrostatic pressure less than 41.9 GPa. Young's modulus anisotropy has been studied and according to 2D and 3D representations of its dependence along the different crystallographic directions, we have found that it is largely anisotropic. The effective on-site Coulomb interaction parameter "Ueff" was estimated by constrained-LDA method “cLDA” to treat the strong correlation of Uranium 5f-electrons. Based on Ueff value estimated by cLDA, GLLB-SC and mBJ potentials were used to predict the band-gap of KUO3 from which it was found to be indirect with X-Γ type and its value is very close to that of direct with Γ-Γ type. The quantum theory of atoms in molecules (QTAIM) was used for a detailed analysis of chemical bonding nature between the different atoms forming KUO3 from where we have found that the ionic character is predominant. This study also made it possible to determine the partitioning of the bulk modulus into atomic basins contributions, from which it has been found that its total value is very close to that found in structural part.

Stable isotope labeling derivatization and magnetic dispersive solid phase extraction coupled with UHPLC-MS/MS for the measurement of brain neurotransmitters in post-stroke depression rats administrated with gastrodin

Synchronous measurement of brain neurotransmitters and blood drug metabolism by dual sites in vivo microdialysis can provide very important information for several neurological disorders such as post-stroke depression (PSD). In this work, d0/d3-6-N-methyl-rhodamine 6G-N-hydroxysuccinimidyl formate (d0/d3-MRSF) were firstly designed, synthesized and used as stable isotope labeling derivatization reagents for the determination of multiple neurotransmitters by ultra-high performance liquid chromatography-tandem mass spectrometry. The light d0-MRSF was used to label neurotransmitters in real samples and the heavy d3-MRSF was used to label standards, which served as internal standards for quantification to minimize matrix effect. The d0/d3-MRSF-neurotransmitter derivatives were easily adsorbed onto the surface of Fe3O4@graphene oxide. Magnetic dispersive solid phase extraction followed with stable isotope labeling derivatization was developed for efficient sample pretreatment. The permanent positively charged moiety of d0/d3-MRSF significantly enhanced the ionization efficiency of neurotransmitters. The comparison results indicated that the synthesized MRSF derivatization method can bring better detection sensitivity than the commercial dansyl chloride method about tens to hundreds of times on the same instrumentation. Specific and regular product ions of m/z 413.3 and 416.3, m/z 429.4 and 432.4 were observed for d0-and d3-MRSF labeled neurotransmitters, respectively. The limits of detection were in the range of 2.0–40.0 pM. The accuracies ranged from 92.3% to 108.2% with the intra- and inter-day precisions in the range of 2.2–12.8%. Synchronous and dynamic determination of concentrations changes of brain neurotransmitters and blood gastrodin of PSD rats was achieved. The results indicated that gastrodin had analogous regulating effect of brain neurotransmitter, which like the clinical medicine fluoxetine of PSD. Taken together, the developed method was demonstrated to be promising for sensitive, accurate and simultaneous determination of multiple neurotransmitters in trace biofluids.

Magnetic ground state and optoelectronic properties of GdMg, GdMg2 and GdMg3 investigated by GGA+U calculations

The present work is a study of the magnetic ground state and optoelectronic properties of GdMg, GdMg2 and GdMg3 using FP-(L)APW + lo method as implemented in WIEN2k code. GGA-PBE has been used as exchange-correlation functional for the prediction of structural properties as well as the most stable magnetic phase. The obtained results are in agreement with the previous results; they indicate that at the ground state, GdMg is ferromagnetic whereas GdMg2 and GdMg3 are antiferromagnetic. To ensure a suitable accuracy for the optoelectronic study of these compounds, the effective Coulomb interaction term “U” between 4f-electrons of Gadolinium atom was determined by constrained LDA “cLDA”. The total and partial magnetic moments values confirm the results of the most stable magnetic phase. The electronic study of these compounds indicates that they are all metallic. The optical properties were studied after the determination of the dielectric function of the different compounds taking into account the intra-band transitions which have a significant contribution in metals. Several optical magnitudes have been determined including the possible inter-band and intra-band electronic transitions as well as the evolution of the optical absorption and the refractive index under the effect of excitation by photon energy.

Study of magnetic and optoelectronic properties of BaCmO3-Cubic Perovskite after the estimation of Hubbard interaction and Hund's exchange parameters: GW and DFT + U investigations

The main objective of this work is the prediction of mechanical stability, magnetic and optoelectronic properties of BaCmO3-Cubic Perovskite by FP-(L)APW + lo method which is implemented in WIEN2k code. The structural parameters and the elastic constants were determined using GGA as exchange-correlation functional and the energy analysis of the most stable magnetic phase showed that BaCmO3 is ferromagnetic. The elastic properties confirmed the mechanical stability of this compound and by their knowledge; several related mechanical parameters were determined. This compound is based on Curium which has highly correlated electrons and since GGA semilocal functional does not accurately treat the electronic properties of this kind of compound, it has been corrected by the estimation of Hund’s exchange “J” and Hubbard interaction “U” parameters by two different methods that are Constrained DFT “cLDA” and constrained Random Phase Approximation “cRPA”. GW approximation with GGA + U as a starting point (GW@GGA + U) was also used for the prediction of the electronic properties of this compound and this choice is motivated by its proven success for this kind of study. The electronic properties have shown that BaCmO3-Cubic Perovskite is a half-metal with a total magnetic moment of ∼6 μB. The optoelectronic transitions between the valence band top and the conduction band bottom have been identified by an analysis of the real and imaginary part variations of the dielectric function.

Electron correlation and spin-orbit coupling effects in scandium intermetallic compounds ScTM (TM = Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag and Au)

Spin-polarized density functional calculations are performed to study the correlation and spin-orbit coupling (SOC) effects in scandium intermetallic compounds viz. ScTM (TM[Formula: see text]=[Formula: see text]Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag and Au) using FP-LAPW[Formula: see text]+[Formula: see text]lo method. The LDA, LDA[Formula: see text]+[Formula: see text]U and LDA[Formula: see text]+[Formula: see text]U[Formula: see text]+[Formula: see text]SOC exchange-correlation functionals are used to calculate the structural parameters and we found that the LDA[Formula: see text]+[Formula: see text]U results are consistent with the experiments. The electronic properties reveal that these compounds are metallic in nature. Correlations effects are determined using the U/W ratio and we found that ScCo, ScIr, ScPd, ScPt, ScCu and ScAg are highly correlated compounds, whereas ScRh, ScNi and ScAu are intermediately correlated compounds. Furthermore, stable magnetic phase for each compound is optimized, which reveals that ScCo, ScRh, ScPd, ScPt and ScCu are stable in ferromagnetic phase, ScIr, ScNi and ScAu are anti-ferromagnetic, whereas ScAg is a nonmagnetic material.

First-principles investigations on the structural, elastic, phase stability and electronic properties of the binary monopnictide compounds based on the fermium FmX (X = P, As, and Sb)

This study is focused on the structural, elastic and electronic properties of fermium monopnictide compounds FmX (X = P, As, and Sb) in rock-salt (B1), CsCl (B2), and zinc-blend (B3) structures using the first-principles Full-Potential Linearized Augmented Plane Waves plus local orbitals (FP-L/APW+lo) method, implemented in the WIEN2k code which including the Generalized Gradient Approximation (GGA) and GGA+U as exchange correlation potential. The structural properties were calculated in order to determine the most stable structure and the most stable magnetic phase. Through our structural investigations, we have concluded that these three binaries doesn't exhibit a magnetic nature, certified by nonmagnetic stable phase in nonmagnetic state. The structural obtained results are presented as, lattice constant (a), bulk modulus (B), and its first pressure derivative (B′). The elastic aggregates properties including elastic constants (Cij), Young's modulus (E), shear modulus (G), Poisson's ratio (υ), Keinman parameter (ζ), and anisotropy factor (A). All the compounds are characterized as brittle and anisotropic materials. The electronic structure of these compounds is described by the exhibition of total and partial densities of states (TDOS and PDOS) and band structures. All the compounds are confirmed as metallic materials. The negative values of formation (Ef) reveal that all the compounds are thermodynamically stable.

Mechanical and magneto-opto-electronic investigation of transition metal based fluoro-perovskites: An ab-initio DFT study

Detailed ab-initio calculations are performed to investigate structural, elastic, mechanical, magneto-electronic and optical properties of the KXF3 (X = V, Fe, Co, Ni) fluoro-perovskites using Full Potential Linearized Augmented Plane Wave (FP-LAPW) method within the framework of density functional theory (DFT). The calculated structural parameters by DFT and analytical methods are found consistent with the experimental results. From the elastic and mechanical properties, it can be inferred that these compounds are elastically stable and anisotropic while KCoF3 is harder than rest of the compounds. Furthermore, thermal behavior of these compounds is analyzed by calculating Debye temperature (θD). The calculated spin dependent magneto-electronic properties in these compounds reveal that exchange splitting is dominated by N-3d orbital. The stable magnetic phase optimizations verify the experimental observations at low temperature. Type of chemical bonding is analyzed with the help of variations in electron density difference distribution that is induced due to changes of the second cation. The linear optical properties are also discussed in terms of optical spectra. The present methodology represents an influential approach to calculate the whole set of mechanical and magneto-opto-electronic parameters, which would support to understand various physical phenomena and empower device engineers for implementing these materials in spintronic applications.

The investigation of electronic, magnetic, mechanical, and lattice dynamical properties of PdMX (M = Cr, Fe and X = Si and Ge) ferromagnetic half-Heusler metallics: an ab initio study

PdMX (M = Cr, Fe and X = Si, Ge) half-Heusler alloys, have been investigated in cubic C1b crystal structure which conforms to space group by using local spin density approximation (LSDA) within the density functional theory (DFT). Firstly, for all materials, the most stable structural phase, which is type-II phase, has been determined. Then, all materials have been considered in ferromagnetic (FM), paramagnetic (PM) and antiferromagnetic (AFM) orders in the most stable type-II structure. The estimated Curie temperatures by using energy differences between FM and PM phases in mean field approximation have been found to be noticeably higher than the room temperature. After the determination of the most stable magnetic phase, their full structural, mechanical, electronic, and lattice dynamical properties have been studied in the most stable magnetic and structural phase. The calculated electronic band structure and total electronic density of states (DOS) have showed that there is no band gap revealing metallic behavior. The estimated elastic constants and calculated phonon dispersion curves have confirmed the stability of FM phase, both mechanically and dynamically.

Gd 도핑된 비스무스 텔루라이드의 자기적 성질에 대한 제일원리 계산 연구

Dept. of Nano Physics, Sookmyung Women’s University, Seoul 04310, Korea(Received 8 April 2016, Received in final form 18 April 2016, Accepted 19 April 2016)Determination of the structural, electronic, and magnetic properties of the magnetically doped bismuth-telluride alloys are drawing lots ofinterest in the fields of the thermoelectric application as well as the research on magnetic interaction and topological insulator. In this study,we performed the first-principles electronic structure calculations within the density functional theory for the Gd doped bismuth-telluridesin order to study its magnetic properties and magnetic phase stability. All-electron FLAPW (full-potential linearized augmented plane-wave) method is employed and the exchange correlation potentials of electrons are treated within the generalized gradient approximation.In order to describe the localized f-electrons of Gd properly, the Hubbard +U term and the spin-orbit coupling of the valence electrons areincluded in the second variational way. The results show that while the Gd bulk prefers a ferromagnetic phase, the total energy differencesbetween the ferromagnetic and the antiferromagnetic phases of the Gd doped bismuth-telluride alloys are about ~1 meV/Gd, indicating thatthe stable magnetic phase may be changed sensitively depending on the structural change such as defects or strains.Keywords : ferromagnetic, magnetic phase stability, thermoelectric, electronic structures calculation, spin-orbit coupling effect,magnetic doping

Theoretical studies of the osmium based perovskites AOsO3 (A=Ca, Sr and Ba)

Osmium based perovskites AOsO3 (A=Ca, Sr and Ba) have been studied theoretically using density functional theory approach. These studies show that CaOsO3 and SrOsO3 are orthorhombic and BaOsO3 is cubic and are consistent with the experiments. The electronic band structures demonstrate that these compounds are metals. The magnetic studies verify the experimental observations at low temperature, where the spin effects are canceled by the orbitals. The stable magnetic phase optimizations and magnetic susceptibilities calculations by the post-DFT treatment confirm that CaOsO3 and SrOsO3 are weak ferromagnetic whereas BaOsO3 is a paramagnetic material. The directional magnetic study shows that these compounds are magnetically anisotropic, and reveals that the easy magnetization axis is [001] direction.

Structural and magnetic properties of TlTF3 (T=Fe, Co and Ni) by hybrid functional theory

DFT studies are performed to investigate the structural, mechanical and magneto-electronic properties of the TlTF3 (T=Fe, Co and Ni) perovskites for the first time using GGA, GGA+U and hybrid density functional theory (HF). Our calculations show that HF give better results than GGA and GGA+U and more consistent with the experiments. The comparison of the lattice constants calculated by HF with experiments shows a maximum underestimation less than 0.2%. The chemical bonding between different ions in these compounds is explained on the bases of electronic clouds, which reveals that in TlFeF3, Fe has more ionic character with F than the rest. The mechanical properties explain the hardness of these compounds and show that TlFeF3 is more ductile. Spin-dependent electronic band profiles show that TlFeF3 and TlCoF3 are metallic, whereas TlNiF3 is pseudo direct wide bandgap semiconductor. The stable magnetic phase optimizations and the calculated magnetic susceptibility confirm that TlFeF3 and TlNiF3 are ferromagnetic whereas TlCoF3 is anti-ferromagnetic material.

Electric-field induced ferromagnetic phase in paraelectric antiferromagnets

The phase diagram of a quantum paraelectric antiferromagnet EuTiO${}_{3}$ under an external electric field is calculated using Landau-Ginzburg-Devonshire theory. The application of an electric field $E$ in the absence of strain leads to the appearance of a ferromagnetic (FM) phase due to the magnetoelectric (ME) coupling. At an electric field greater than a critical field, ${E}_{cr}$, the antiferromagnetic (AFM) phase disappears for all considered temperatures, and FM becomes the only stable magnetic phase. The calculated value of the critical field is close to the values reported recently by Ryan et al. [Nat. Commun. 4, 1334 (2013)] for EuTiO${}_{3}$ film under a compressive strain. The FM phase can also be induced by an $E$-field in other paraelectric antiferromagnetic oxides with a positive AFM-type ME coupling coefficient and a negative FM-type ME coupling coefficient. The results show the possibility of controlling multiferroicity, including the FM and AFM phases, with help of an electric field application.

ChemInform Abstract: Structural and Magnetic Properties of Nd17Fe76(B1-xCx)7 Alloys

The influence of partial C substitution for B on structural and magnetic properties of Nd17Fe76(B(1-x)C(x))7 alloys has been studied. It has been discovered that the stable hard magnetic phase Nd2Fe14(B,C) with the tetragonal structure can be formed if x < 0.9. As the C content increases, the lattice constant a is nearly constant whereas c decreases linearly. Furthermore, with increasing C content , the microstructure of cast alloys and sintered magnets varies. The temperature dependence of the anisotropy field H(A) and the coercivity i(H)c of the Nd17Fe76(B(1-x)C(x)7 alloys was measured from room temperature up to about 300-degrees-C. The anisotropy field H(A) increases whereas the coercivity i(H)c decreases greatly with increasing C content.

Ferrimagnetic Fe-doped GaN: An unusual magnetic phase in dilute magnetic semiconductors

Most dilute magnetic semiconductors exist either in ferromagnetic (e.g., GaAs:Mn) or antiferromagnetic (ZnSe:Mn) phases at low temperature. This alignment persists even after carriers are introduced, although the preference may change as a function of doping. Using first-principles calculations, we found that the stable magnetic phase of GaN:Fe is ferrimagnetic under hole doping, in which the nearest Fe atoms have antiparallel spins with different magnetic moments. This unusual behavior is explained by the Stoner model combined with a band coupling model. Furthermore, the consequences of the formation of the ferrimagnetic phase in diluted magnetic systems are discussed.

Hybrid perovskite-spinel magnetic tunnel junctions based on conductive ferrimagnetic NiFe2O4

Ultrathin epitaxial films of NiFe2O4, when grown under specific conditions, show a large enhancement of their magnetic moment and electrical conductivity. This allowed us to use such layers as electrodes in magnetic tunnel junctions. In this paper, we report on the observation of a large tunnel magnetoresistance at low temperature in La2∕3Sr1∕3MnO3∕SrTiO3∕NiFe2O4 junctions. From these results we infer a spin polarization of up to 45% for NiFe2O4, which stays constant up to ∼300K. NiFe2O4 can therefore be considered as an alternative to Fe3O4 as a high-temperature spin-polarized Fe oxide. Furthermore, our findings provide a way to design materials for spintronics based on the stabilization of nonthermodynamically stable magnetic phases of spinel oxides.

Magnetic Dead Layers Induced by Strain at fct Fe/Rh(001) Interface

We have studied magnetic properties of face-centered-tetragonal (fct) Fe thin films grown at room temperature on the Rh(001) surface. Band structure calculations show that the stable magnetic phase of fct Fe on the Rh(001) surface is ferromagnetic (FM), which agrees with our previous conclusion obtained by angle-resolved photoelectron spectroscopy and spin- and angle-resolved photoelectron spectroscopy (SARPES) of the four monolayers (ML) Fe film [K. Hayashi et al. : Phys. Rev. B 64 (2001) 054417]. This magnetic phase of fct Fe is also confirmed by the SARPES spectra of 3 ML Fe/Rh(001). On the other hand the thickness dependence of the Curie temperature estimated by SARPES and of local magnetic moment by soft X-ray magnetic circular dichroism experiments show that the Fe films below 2 ML are not FM, i.e., they are magnetic dead layers. We conclude that these magnetic dead layers are caused by a large strain at the Fe/Rh(001) interface.