Temperature Dependence Of Magnetic Moment Research Articles

Temperature dependence of magnetic moment of rare earth ions in ErFeO3 and NdFeO3 single crystals.

The interaction between rare earth and iron spins in rare earth orthoferrites leads to remarkable phenomena, such as the spin-flip process. This is despite the rare earth spins not being magnetically ordered. Instead, they are polarized by the ordered iron spins. The interaction between the two spin families is not well understood. This study reports the temperature dependence of the net magnetic moment for rare earth spins, by measuring the overall magnetization for ErFeO3 and NdFeO3 single crystals. The obtained temperature dependence can be described well using a model based on the mean field theory, giving tanh(const./T) temperature dependence. This functional dependence is not disrupted by the spin-flip transition as the crystals are cooled.

The effect of defects formed under pressure on CuCrO2 delafossite

Pressure-dependent delafossite CuCrO2 samples are synthesized by the solid-state reaction method to investigate the effect of defects formed under pressure on the structure and magnetic properties of CuCrO2. X-ray Diffractometer, Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS), Photoluminescence spectroscopy (PL), and Vibrating Sample Magnetometer (VSM) are used the characterize CuCrO2 samples. All samples give almost the same structural phase properties without any secondary peaks. All magnifications of SEM images show no melting of the sample and thus the annealing temperature of the samples is optimized. Photoluminescence measurements reveal that near band emission is caused by excitonic transitions between electrons and holes, the stronger the UV emission of the sample, the higher the crystallization quality, and fewer defects occur. Magnetic investigations depict that the spins are antiferromagnetically oriented while they have a magnetic moment component perpendicular to the plane. Therefore, each grain should be considered a weak magnet. Temperature-dependent magnetic moment measurements exhibit a slight variation in moment values. The reason behind this should be attributed to the grain size related to the formation of grains by applied pressure.

Inverse Faraday Effect for Superconducting Condensates.

The Cooper pairs in superconducting condensates are shown to acquire a temperature-dependent dc magnetic moment under the effect of the circularly polarized electromagnetic radiation. The mechanisms of this inverse Faraday effect are investigated within the simplest version of the phenomenological dynamic theory for superfluids, namely, the time-dependent Ginzburg-Landau (GL) model. The light-induced magnetic moment is shown to be strongly affected by the nondissipative oscillatory contribution to the superconducting order parameter dynamics, which appears due to the nonzero imaginary part of the GL relaxation time. The relevance of the latter quantity to the Hall effect in the superconducting state allows us to establish the connection between the direct and inverse Faraday phenomena.

Computational analysis of anomalous temperature dependence of magnetic properties in Mn4C compound

We have calculated electronic structures of Mn4C using first-principles calculations based on density functional theory (DFT) within the Perdew Burke Ernzerhof-generalized gradient approximation (PBE-GGA). The calculated band structures and density of states (DOS) indicate that stability of cubic perovskite-type crystal structured Mn4C is originated from p-d hybridization between Mnb and C and d-d hybridization between Mna and Mnb sublattices. The mean field approximation (MFA) resulted in the Néel temperature (TN) of 879 K which is in close agreement with experimental TN. The temperature dependence of magnetic moments of Mna and Mnb sublattices were also calculated using the Brillouin function to investigate the origin of unusual linearly increasing magnetization below 400 K. It was found that the increasing magnetization is originated from strong mutual interdependence of more or less linearly decreasing magnetic moment of Mna and stationary magnetic moment of Mnb below 400 K.

Investigation of Magnetic Anisotropy in the Ni-Ge and Ni(NiO)-Ge Thin Films

We studied the structural and magnetic properties of Ni-Ge and Ni(NiO)-Ge films deposited by physical vapor deposition technique on the Si/SiO2 substrate. The x-ray diffraction (XRD) analysis show that as-prepared samples exhibit clear peaks of Ge, Ni, and Au with a cubic symmetry belongs to space group Fm3¯m. Due to the thermal annealing process at 350°C, NiO layer formed on Ni layer. The NiO formation has reduced the interaction of Ni-Ge interlayer which is confirmed by XRD data. Investigation of temperature-dependent magnetic moment revealed the Neel and the critical temperatures as 93 and 294 K, respectively. The hysteresis loops showed that the preferred magnetization direction for samples at 300 K is the in-plane (parallel) which reaches saturation easier than out-of-plane (perpendicular) loops. The formation of NiGe interlayer resulted in a magnetically dead-region which led to decrease ferromagnetic domain and the coercive field.

Variation of effective damping with temperature in permalloy/Gd heterostructures

In this study, we systematically investigate the temperature dependence of effective damping in FeNi (permalloy or Py)/Gd bilayer based on broadband ferromagnetic resonance. Despite a significant increase in the effective damping of the Py/Gd bilayer with decreasing temperature, we show that the spin pumping is not responsible for the result. By combining our findings with systematic measurement data of Py/Cu/Gd contrast samples, we conclude that an effective damping enhancement from a decrease in temperature is due to the temperature-dependent magnetic moment of Gd and antiferromagnetic coupling between Py and Gd. Further, we perform a semiquantitative analysis of the experimental data using the Landau-Lifshitz-Gilbert equations that consider the antiferromagnetic coupling between Py and Gd, and estimated the damping parameters in the range of 0.3--0.4 for Gd films with thicknesses of 5 and 8 nm. Our results suggest that to analyze the spin transport in heterostructure with several magnetic layers, it is necessary to commence from the fundamentals of magnetization dynamics considering interlayer coupling and avoid the overuse of spin pumping.

Ni-doped Bi0.5Sb1.5Te3 single crystal: a potential functional material for thermoelectricity, topological insulator, and optoelectronics

We report the growth of Ni-doped Bi0.5Sb1.35Ni0.15Te3 single crystal via the self-flux method. The crystalline nature of a grown single crystal was confirmed by the X-ray diffraction technique (XRD). Interestingly, the XRD pattern shows a sharp reflections of type of planes, revealing the growth of the crystal in c-direction. The grown single crystal was subjected for measurement of field dependence magnetization at 300 K and temperature-dependent magnetic moment. The electronic transport property of bulk single crystal was also carried out in a wide range of temperatures from 150 to 450 K. Reasonably large electrical conductivity σ ~ 1584 S/cm at room temperature was observed which shows ~ 400% enhancement in σ than the electrical conductivity of bare Bi0.5Sb1.5Te3 single crystal (400 S/cm at 300 K). This enhanced electrical conductivity results to significant power factor ~ 1.68 × 10− 3 W/m K2 at 300K which is 163% larger than that of bare Bi0.5Sb1.5Te3 single crystal (6.45 × 10− 4 W/m K2). Magnetic properties of a single crystal of Bi0.5Sb1.35Ni0.15Te3 reveal ferromagnetic behavior at 300 K. The photoluminescence (PL) behavior of Bi0.5Sb1.35Ni0.15Te3 single-crystal was also scrutinized. The PL spectra of Bi0.5Sb1.35Ni0.15Te3 single crystal shows the strong red emission peak in the visible region from 600 to 690 nm upon excitation at 375 nm wavelength, which corresponds to the optical bandgap of 2.1 eV.

Tris(ethylenediamine) Cobalt(II) and Manganese(II) Nitrates

Octahedral tris(ethylenediamine) coordination complexes demonstrate helicoidal chirality, due to the arrangement of the ligands around the metal core. The enantiomers of the nitrate salts [Ni(en)3](NO3)2 and [Zn(en)3](NO3)2 spontaneously resolve to form a mixture of conglomerate crystals, which present a reversible phase transition from space group P6322 to enantiomorphic P6522 or P6122, with the latter depending on the handedness of the enantiomer. We report here the synthesis and characterization of [Mn(en)3](NO3)2 and [Co(en)3](NO3)2, which are isostructural to the Zn(II) and Ni(II) derivatives. The Mn(II) analogue undergoes the same phase transition centered at 150(2) K, as determined by single-crystal X-ray diffraction, Raman spectroscopy, and differential scanning calorimetry. The Co(II) derivative does not demonstrate a phase transition down to 2 K, as evidenced by powder X-ray diffraction and heat capacity measurements. The phase transition does not impact the magnetic properties of the Ni(II) and Mn(II) analogues; these high spin compounds display Curie behavior that is consistent with S = 1 and 5/2, respectively, down to 20 K, while the temperature-dependent magnetic moment for the Co(II) compound reveals a significant orbital contribution.

Mechanical behavior, enhanced dc resistivity, energy band gap and high temperature magnetic properties of Y-substituted Mg–Zn ferrites

We report the synthesis of Y-substituted Mg–Zn [Mg0.5Zn0.5Y x Fe2−x O4 (0 ≤ x ≤ 0.05)] ferrites using conventional standard ceramic technique. The samples were characterized by x-ray diffraction (XRD) analysis, field emission scanning electron microscopy (FESEM), FTIR spectroscopy, UV–Vis spectroscopy and quantum design physical properties measurement system (PPMS). XRD patterns confirm the single phase cubic spinel structure up to x = 0.03 and appearance of a secondary phase of YFeO3 for higher Y contents. FESEM images depict the distribution of grains and EDS spectra confirmed the absence of any unwanted element. Completion of solid state reaction and formation of spinel structure has been revealed from FTIR spectra. The FTIR data along with lattice constant, bulk density and porosity were further used to calculate the stiffness constant (C ij), elastic constant and Debye temperatures. Mechanical stability of all studied compositions is confirmed from C ij using Born stability conditions. Brittleness and isotropic nature are also confirmed using Poisson’s ratio and anisotropy constants, respectively. The enhancement of dc electrical resistivity (105Ω cm to 106Ω cm) with Y content is observed. The energy band gap (increased with Y contents) is found in good agreement with dc electrical resistivity. Ferrimagnetic to paramagnetic phase change has been observed from the field dependent high temperature magnetization curves. The magnetic moments and saturation magnetization were found to be decreased with increasing temperature. The Curie temperature (Tc) has been measured from temperature dependent magnetic moment (M-T) and initial permeability (μ′i-T) measurements and found to be in good agreement with each other. Decrease in Tc with Y content is due to redistribution of cations and weakening of the exchange coupling constant. The magnetic phase transition has been analyzed by Arrott plot and found to have second order phase transition. The dc resistivity endorses the prepared ferrites are suitable for high frequency and high temperature magnetic device applications as well.

Local magnetic study for cluster-layered Fe/Cr nanostructures

Local magnetic structures of cluster-layered Fe/Cr thin films are studied by X-ray magnetic circular dichroism (XMCD) and extended X-ray absorption fine structure (EXAFS). The magnetic moment of Fe atoms evaluated from XMCD for Al2O3/Cr(70Å)/[Fe(1.2Å )/Cr(10.5Å)]30/Cr(12Å), which shows the minimum point in the resistivity, decreases as the temperature increases and disappears around the temperature of the minimum resistivity. EXAFS shows the local structure of this film around Fe atoms is rather disordered and it can be related the fluctuation of magnetic structure estimated from the theoretical analysis of the temperature dependence of magnetic moments.

Competing Electronic Phases near the Onset of Superconductivity in Hole-doped SrFe2As2

An intriguingly complex phase diagram of Na-doped SrFe2As2 is uncovered using high-resolution thermal-expansion, magnetization and heat-capacity measurements. The detailed temperature dependence of the orthorhombic distortion and the anisotropy of the uniform magnetic susceptibility provide evidence for nine distinct electronic phases near the transition region between stripe antiferromagnetism and unconventional superconductivity. In particular, we report the finding of a new magnetic phase which competes surprisingly strongly with superconductivity. From theoretical studies we propose that this phase is a double-Q phase consisting of a mixture of symmetry-distinct commensurate magnetic orders with a peculiar temperature-dependent magnetic moment reorientation.

Fabrication and characterization of YIG nanotubes

Abstract We have successfully synthesized Y3Fe5O12 (yttrium iron garnet, YIG) nanotubes (NTs) of different diameters using a conventional sol-gel method in anodized aluminum oxide (AAO) templates. An annealing process at 800 °C is performed to get a pure phase of YIG. The room-temperature magnetization measurements show that the coercivity decreases significantly as the diameter of nanotubes increases. The temperature dependence of magnetic moments in field-cooled (FC) and zero-field-cooled (ZFC) modes indicates that YIG NTs transform from ferromagnetic-like (FM-like) state to superparamagnetic (SPM) state when temperature decreases (in the region of 310 K–400 K). The Blocking temperature dramatically decreases as the size of YIG NTs reduces. In the FM-like state, the temperature-dependent coercivity in three different samples yields a 1/2 power law of the temperature. The temperature dependence of saturation magnetization in three different samples can be well fitted to Bloch’s T3/2 law. Characterization of ferromagnetic resonance (FMR) is conducted, which indicates the Gilbert damping parameter of YIG NTs is around 7–9 × 10−3.

Voltage-controlled Kosterlitz–Thouless transitions and various kinds of Kondo behaviors in a triple dot device**Project supported by the National Natural Science Foundation of China (Grant No. 11504102), the Scientific Research Items Foundation of Hubei Educational Committee, China (Grant Nos. Q20161803 and B2016091), the Doctoral Scientific Research Foundation (Grant No. BK201407), and the Major Scientific Research Project Pre-funds of Hubei University of

The transport property and phase transition for a parallel triple dot device are studied by adopting Wilson's numerical renormalization group technique, focusing on the effects of level spacings between neighboring dot sites. By keeping dot 2 at the half-filled level and tuning the level differences, it is demonstrated that the system transits from local spin quadruplet to triplet and doublet sequently, and three kinds of Kondo peaks at the Fermi surface could be found, which are separated by two Kosterlitz–Thouless type quantum phase transitions and correspond to spin–3/2, spin–1, and spin–1/2 Kondo effect, respectively. To obtain a detailed understanding of these problems, the charge occupation, the spin—spin correlation, the transmission coefficient, and the temperature-dependent magnetic moment are shown, and necessary physical arguments are given.

Effect of Dot Geometry on Various Kinds of Kondo Behaviors for Parallel Triple Dot System

With the help of the Wilson’s numerical renormalization group technique, we study the dynamical and magnetic properties for a parallel triple dot system with five different dot geometries in the strong correlation limit. We reveal that when the dot configuration changes, several kinds of Kondo effect could be found, i.e., the partially screened spin − 3/2, the totally screened spin − 1, the spin − 1/2, and the spin − 0 Kondo effects, implying numerically that the manners in which the dots and leads are organized play important roles in the Kondo behaviors. To understand these quantum phenomena, the local density of states, the transmission coefficient, the spin-spin correlation function, and the temperature-dependent magnetic moment for each configuration are shown, and necessary theoretical discussions are given.

Kosterlitz–Thouless transition, spectral property and magnetic moment for a two-dot structure with level difference**Project supported by the National Natural Science Foundation of China (Grant No. 11504102), the Special Fund for Theoretical Physics of the National Natural Science Foundation of China (Grant No. 11647133), the Doctoral Scientific Research Foundation of China (Grant No. BK201407), and the Major Scientific Research Project Pre-funds

By means of the numerical renormalization group method, we study the phase transition, the spectral property, and the temperature-dependent magnetic moment for a parallel double dot system with level difference, where the dot energies are kept symmetric to the half-filled level. A Kosterlitz–Thouless (KT) transition between local spin triplet and singlet is found. In the triplet regime, the local spin is partially screened by the conduction leads and spin–1 Kondo effect is realized. While for the singlet, the Kondo peak is strongly suppressed and the magnetic moment decreases to 0 at a definite low temperature. We attribute this KT transition to the breaking of the reflection symmetry, resulting from the difference of the charge occupations of the two dots. To understand this KT transition and related critical phenomena, detailed scenarios are given in the transmission coefficient and the magnetic moment, and an effective Kondo model refers to the Rayleigh-Schrödinger perturbation theory is used.

Magnetic properties of 42CrMo4 steel

Low alloyed high-grade chrome-molybdenum ferritic steel was investigated from the point of views of magnetic properties in dependence on heat and mechanical treatment. This steel can be used as components of magnetic circuits or some parts in electrical equipment. The basic information on structure and phase composition was obtained by optical and scanning electron microscopy, X-ray Powder Diffraction and Mössbauer Spectroscopy. The temperature stability of the material was proved by measurements of temperature dependences of magnetic moment. The magnetic parameters were obtained by measuring of magnetic hysteresis loops in dependence on saturation field and their frequencies. The results are discussed from the point of view of possible applications as a magnetic material in the very extremely environment, where high mechanical stresses and elevated temperatures can occur.

Zinc doped copper ferrite particles as temperature sensors for magnetic resonance imaging

We investigate the use of Cu0.35Zn0.65Fe2O4 particles as temperature-dependent sensors in magnetic resonance imaging (MRI). This material has a Curie temperature near 290 K, but in the large magnetic fields found in MRI scanners, there is a significant temperature-dependent magnetic moment near body temperature; 310 K. When the ferrite particles are doped into an agar gel, the temperature-dependent magnetic moment leads to a temperature-dependent broadening of the NMR linewidth for water protons and to a temperature-dependent image intensity for MRI, allowing one to make temperature maps within objects. The temperature resolution is about 1.3 K.

Sign reversal of magnetization and exchange bias in Ni(Cr1−xAlx)2O4 (x=0–0.50)

Ni(Cr1-xAlx)2O4 (x=0–0.50) samples were prepared in single phase form by using sol-gel method and their structural and magnetic properties were studied. Al substitution transforms the crystal structure of NiCr2O4 from tetragonal cell with space group I41/amd to cubic cell of Fd3¯m space group. Magnetization measurements by varying the temperature and magnetic field were carried out to investigate the interesting magnetization reversal and exchange bias behaviors. Magnetization reversal is observed for x=0.10 sample with a magnetic compensation temperature of 40K and it is explained by considering different temperature dependences of magnetic moments of the two sublattices. Shifting of magnetic hysteresis loops towards the negative magnetic field axis and hence the presence of negative exchange bias field is observed for x=0.15 sample. The x=0.10 sample exhibits the tunable positive and negative exchange bias field. Exchange bias in these samples is explained considering the anisotropic exchange interaction between the ferrimagnetic and the antiferromagnetic components of magnetic spins. However, the sign reversal of exchange bias field is due to the change in domination of one ferrimagnetic sublattice over the other with variation in temperature. Both normal and inverse magnetocaloric effects are observed for x=0.10 sample.

The numerical investigation of magnetic properties of single domain MnP:GaP nanoparticles

The magnetic properties of MnP:GaP nanoparticles are calculated using a statistical mechanical approach and effect of various factors on magnetization of nanoparticles is studied. The calculation is based on solution of localized partition function and evolution of magnetic moment affected by thermal fluctuation and external field is included by solving master equation. Instead of constant magnetic saturation approximation, a temperature dependent magnetic moment saturation is included to improve calculation efficiency for larger nanoparticles. In the present work, the field-cooled and zero-field-cooled (FC/ZFC) magnetization of randomly oriented anisotropy and log-normal volume distributed nanoparticles are calculated.

Phase diagram and low temperature scenario for a triangular triple dot system

We present a triangular triple quantum dot (TTQD) system with two dots connected parallelly to one conduction lead, and investigate the phase diagram, the electric transport, and the temperature-dependent magnetic moment at half filling. When the hopping between two connected dots t12 = 0, and those between the connected dots and the side dot are symmetric t13 = t23, two connected dots form a spin triplet due to the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction mediated by the dot-lead coupling and/or the hopping t13 (t23). For t13 = 0, the triplet is partially screened by the conduction leads at low temperature. Both the connected dots and the side dot contribute to the magnetic moment of the system. For any definite t13, the triplet is totally screened by the conduction leads and the side dot, and the two-stage Kondo effect occurs. When t12 increases beyond a critical t12c, two connected dots form a spin singlet and decouple from the side dot. In this case, the Kondo peak is strongly suppressed, indicating zero conductance, and only the localized side dot contribute to the magnetic moment at low temperature. When t13 ≠ t23, we find a crossover as t12 increases, contrast to the first order transition of the symmetric case. Numerical renormalization group technique and physical arguments are used to obtain a detailed understanding of these problems.