Dc Magnetic Properties Research Articles

Crystal Structure and Magnetic Properties of an Oxamato‐Bridged Heterobimetallic Tetranuclear [NiIICuII]2 Complex of the Rack Type

This work discusses a new heterobimetallic nickel(II)–copper(II) complex of the formula [Ni(tpa)Cu(opba)]2·6H2O (1) {H4opba = N,N′‐1,2‐phenylenebis(oxamic acid) and tpa = tris(2‐pyridylmethyl)amine}. The molecular structure of 1 consists of neutral tetranuclear species with a 4R rack‐type architecture featuring two NiIICuII dinuclear units connected through two out‐of‐plane oxo(carboxylate‐oxamate) atoms from the opba ligands. The crystal packing of 1 exhibits a supramolecular 1D arrangement of tetranuclear entities connected by hydrogen bonds and π–π stacking interactions. The dc magnetic properties of 1 were interpreted according to its dimer‐of‐dimer structure; the spin Hamiltonian being defined as {H = –J[SNi1·SCu1 + SNi1ⁱ·SCu1ⁱ – jeff(SCu1·SCu1ⁱ)]}. The analysis of the magnetic data shows the occurrence of a strong intradimer antiferromagnetic coupling between the NiII and CuII ions [J = –115.2(4) cm–1] and a weak interdimer antiferromagnetic coupling between the CuII ions [jeff = –1.12(7) cm–1]. DFT‐type calculations were performed to visualize the exchange pathway through the oxamate bridge and substantiate the value of J.

AC and DC electrical conductivity, dielectric and magnetic properties of Co0.65Zn0.35Fe2−x Mo x O4 (x = 0.0, 0.1 and 0.2) ferrites

Cobalt–Zinc ferrites are an important material for designing multiferroic composite. The Mo (4d-transition metal) doped Cobalt–Zinc ferrites are synthesized using ceramic (solid-state reaction) method. Investigation of detailed ac and dc electrical conductivity, dielectric and magnetic properties of Co0.65Zn0.35Fe2−x Mo x O4 (x = 0.0, 0.1 and 0.2) spinel ferrites have been reported here. The recorded XRD pattern confirms the formation of inverse spinel structure of the material. The dielectric dispersion has been studied in detail and the existence of non-Debye type relaxation behavior has been confirmed. The dielectric tangent loss is found to be very small at high frequency. The ac conductivity follows the correlated barrier hopping like model. Also the conduction process can be best explained on the basis of Verwey-de Boer mechanism. Magnetic phase transition of the material is estimated from magnetization vs. temperature plots.

Cyanido-Bridged {LnIIIWV} Heterobinuclear Complexes: Synthesis and Magneto-Structural Study

A new series of cyanido-bridged {LnIIIWV} heterobinuclear complexes of formula [LnIII(pyim)2(i-PrOH)(H2O)2(μ-CN)WV(CN)7]·2H2O [Ln = Gd (1), Tb (2), Dy (3), Ho (4), and Er (5); pyim = 2-(1H-imidazol-2-yl)-pyridine) and i-PrOH = isopropyl alcohol] were synthesized by one-pot reaction between (NH3Bu)3[W(CN)8] and [Ln(pyim)2]2+ complexes (generated in situ by mixing the corresponding LnIII ions and the pyim ligand). Compounds 1-5 are isomorphous and crystallize in the monoclinic system P21/n space group. Their crystal structure consists of binuclear units in which the octacyanotungstate(V) anion coordinates to the corresponding LnIII ion through a single cyanide ligand. The tungsten(V) and lanthanide(III) ions are eight-coordinated, in distorted square antiprism (WV) and distorted trigonal dodecahedron (LnIII) geometries, respectively. The direct-current (dc) magnetic properties for 1-5 reveal the occurrence of weak antiferromagnetic interactions between WV and LnIII cation, with 8S7/2, 7F6, 6H15/2, 5I8, and 4I15/2 as ground terms for GdIII, TbIII, DyIII HoIII, and ErIII, respectively [JWLn = -1.19(1) (1), -1.02(2) (2), -1.10(2) (3), -1.30(2) (4), and -1.50(3) cm-1 (5), the spin Hamiltonian being defined as H = -JWLn SW·SLn]. The fit of the χMT data of 2-4 points out a positive value for the energy gap between the ML components (Δ). This feature is corroborated by their Q-band electron paramagnetic resonance spectra at low temperature, which clearly show MJ = 0 (2 and 4) and ±1/2 (3 and 5). Incipient frequency-dependent alternating-current magnetic susceptibility signals are observed for 3 and 5 under applied dc fields supporting the presence of slow magnetic relaxation behavior, the blocking temperatures being below 2.0 K. This new series of {LnIIIWV} heterobinuclear compounds provides more insights into the exchange magnetic interaction between 5d and 4f centers via the cyanide-bridge, for which scarce information is available to date.

Influence of Terfenol-D Powder Volume Fraction in Epoxy Matirx Composites on their Magnetomechanical Properies

Abstract In this paper the investigations of magnetostriction as well as DC magnetic properties for composites doped with Terfenol-D particles are presented. All investigations were performed for the materials with 35%, 46% and 70% volume fraction of the Terfenol-D particles surrounded by epoxy matrix. Moreover, the bulk Terfenol-D alloy was tested. The obtained results show that the magnetization of the composite materials increases with increasing the volume fraction of Terfenol-D particles. Similar dependence as for magnetization was observed for the magnetostriction measurements. Although the magnetostriction of composite material is smaller than for solid Terfenol-D it is still tens of times bigger than in case of traditional magnetostrictive materials. Obtained results gives opportunity to use these materials for variety applications such as actuators and sensors.

DC Magnetic Properties and Complex Permeability of Ni-Fe Based Composites

DC Magnetic Properties and Complex Permeability of Ni-Fe Based Composites

DC Magnetic Properties of Amorphous Vitrovac Ribbon

DC Magnetic Properties of Amorphous Vitrovac Ribbon

Magnetic coupling of stripe domains in FePt/Ni80Fe20 bilayers

Equiatomic FePt in the A1 soft magnetic phase and Ni80Fe20 (permalloy) thin films form a stripe-like magnetic domain structure above a critical thickness. This critical thickness is considerably different in the two alloys and allows us to study the influence of the magnetic coupling in the domain configuration in bilayers. Using dc magnetron sputtering techniques, we fabricated two different sets of FePt/Ni80Fe20 bilayers, keeping one thickness fixed and varying the other, and investigated the dc magnetic properties and the magnetic domain configuration of the structure. In all cases, magnetization reversal occurred at a single coercive field, indicating a relatively strong magnetic exchange coupling between both layers. The observed stripe period was also consistent with a model of spring magnet-like behavior. However, for certain values of FePt and permalloy thickness a complex nonparallel double stripe structure was found, which may be attributed to the influence of the dipolar stray field of the thicker layer on the stripe structure of the thinner film.

A rapid and efficient thermal decomposition approach for the synthesis of manganese-zinc/oleylamine core/shell ferrite nanoparticles

This paper presents the effect of adding different amounts of zinc into the composition of Zn-Mn/oleylamine core/shell ferrite nanoparticles (NPs). For this purpose, acetylacetonate as a main precursor, oleylamine as a surfactant and surface modifier, and stearyl alcohol as a co-surfactant were used for thermal decomposition synthesis of this ferrite. Monodispersed core/shell ferrite NPs synthesized with several compositions. The X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images showed single-phase nanoparticles around 10 nm without any impurities. Fourier Transform Infrared Spectroscopy (FTIR) confirmed single-phase spinel with ultra-thin layers of oleylamine on the surfaces that make the particles separated from each other. Thermogravimetric studies could also measure the amount of surfactant around the NPs. Moreover, the DC magnetic properties of the samples were studied using the vibrating sample magnetometer (VSM). The M-H curves for all the samples showed negligible hysteresis loops indicating the superparamagnetic behaviour of the NPs. Furthermore, maximum saturation magnetization was measured for the sample with Mn0.6Zn0.4Fe2O4 with 45 amu.gr−1, suggesting that this composition could be an excellent candidate for biomedical applications such as hyperthermia and imaging.

Optical and magnetic nanocomposites containing Fe3O4@SiO2 grafted with Eu3+ and Tb3+ complexes

The fabrication of bifunctional nanocomposites, co-assembling photonic (RE3+) and magnetic (Fe3O4) features into single entity nanostructures is reported through a facile method, using Fe3O4 as core nanoparticles, which were coated with SiO2 shell and further grafted with Eu3+ and Tb3+ complexes. The sophisticated structural features and morphologies of the core-shell Fe3O4@SiO2-(TTA-RE-L) nanomaterials were studied by Small-angle X-ray Scattering. The core mean size 〈DSAXS〉, shell thickness ΔR, cluster size ξ and fractal dimension DF were determined by fitting the experimental SAXS data, corroborating through Transmission Electron Microscopy images. The DC magnetic properties at temperatures of 2 and 300 K were explored in support to the structural conclusions from SAXS and TEM analyses. The magnetic contributions of the RE3+ ions to the magnetizations of the Eu3+ and Tb3+ nanocomposites were discussed. The photoluminescence properties of the Eu3+ and Tb3+ nanocomposites based on the emission spectral data and luminescence decay curves were studied. The experimental intensity parameters (Ωλ), lifetimes (τ), emission quantum efficiencies (η) as well as radiative (Arad) and non-radiative (Anrad) decay rates were calculated and discussed, in addition, the structural conclusions from the values of the 4f-4f intensity parameters in the case of the Eu3+ ion. These novel Eu3+ and Tb3+ nanocomposites may act as red and green emitting layers for magnetic and light converting molecular devices.

Rapid fabrication and characterization of spherical Mumetal nanoparticles by an electrical wire explosion process

abstractSpherical Mumetal nanoparticles fabricated by the electrical wire explosion process in 1% solution of poly(acrylamide-co-acrylic acid) partial sodium salt as the explosion medium and capping agent to prevent particle agglomeration and control the size of nanoparticles. The structure, morphological features were studied by field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and Transmission Electron Microscope (TEM). The size distribution and the principle elements analysis of Mumetal nanoparticles were analyzed. The DC magnetic properties of Mumetal nanoparticles were carried out on a Quantum Design superconducting quantum interference device (SQUID) and the temperature-dependence of mass magnetic susceptibility χ (T) and its inverse 1/χ for the Mumetal nanoparticles were measured in field-cooling (FC) procedures in an applied magnetic field of 50000 Oe between 2 and 300 K.

Dc and ac magnetic properties of thin-walled Nb cylinders with and without a row of antidots

dc and ac magnetic properties of two thin-walled superconducting Nb cylinders with a rectangular cross-section are reported. Magnetization curves and the ac response were studied on as-prepared and patterned samples in magnetic fields parallel to the cylinder axis. A row of micron-sized antidots (holes) was made in the film along the cylinder axis. Avalanche-like jumps of the magnetization are observed for both samples at low temperatures for magnetic fields not only above Hc1, but in fields lower than Hc1 in the vortex-free region. The positions of the jumps are not reproducible and they change from one experiment to another, resembling vortex lattice instabilities usually observed for magnetic fields larger than Hc1. At temperatures above and the magnetization curves become smooth for the patterned and the as-prepared samples, respectively. The magnetization curve of a reference planar Nb film in the parallel field geometry does not exhibit jumps in the entire range of accessible temperatures. The ac response was measured in constant and swept dc magnetic field modes. Experiment shows that ac losses at low magnetic fields in a swept field mode are smaller for the patterned sample. For both samples the shapes of the field dependences of losses and the amplitude of the third harmonic are the same in constant and swept field near Hc3. This similarity does not exist at low fields in a swept mode.

Synthesis and characterization of Fe0.6Zn0.4Fe2O4 ferrite magnetic nanoclusters using simple thermal decomposition method

This paper presents experimental results regarding the effect of the quantity of solvent on formation of the Fe–Zn ferrite nanoparticles during thermal decomposition. A ternary system of Fe0.6Zn0.4Fe2O4 has been synthesized by a thermal decomposition method using metal acetylacetonate in high temperature boiling point solvent and oleic acid. The X-ray diffraction study was used to determine phase purity, crystal structure, and average crystallite size of iron–zinc ferrite nanoparticles. The average crystallite size of nanoparticles was increased from 13nm to 37nm as a result of reducing the solvent from 30ml to 10ml in a synthesis batch. The diameter of particles and morphology of the particles were determined by transmission electron microscopy (TEM) and field emission scanning electron microscope (FESEM). Mid and far Fourier transform infrared (FT-IR) measurement confirmed monophasic spinel structure of ferrite. Furthermore, the DC magnetic properties of the samples were studied using the vibrating sample magnetometer (VSM). The largest Fe–Zn ferrite nanoparticles exhibited a relatively high saturation magnetization of 96emu/g. Moreover, Low-field AC susceptibility measurement indicated blocking temperature of nanoparticles around 170–200K.

Effect of Si addition on AC and DC magnetic properties of (Fe-P)-Si alloy

We report a new (Fe-P)-Si based alloy with relatively high induction (1.8-1.9 T), low coercivity (< 80 A/m), high resistivity (∼38 μΩ cm) and low core loss (217 W/kg @ 1 T/1 kHz) comparable to the commercially available M530-50 A5 Si-steel. The attractive magnetic and electrical properties are attributed to i) the two phase microstructure of fine nano precipitates of Fe3P dispersed in α-Fe matrix achieved by a two-step heat-treatment process and ii) Si addition enhancing the resistivity of the α-Fe matrix phase. As the alloy processing is by conventional wrought metallurgy method, it has the potential for large scale production.

Non-conductive ferromagnetic carbon-coated (Co, Ni) metal/polystyrene nanocomposites films

This article reports non-conductive ferromagnetic properties of metal/polymer nanocomposite films intended to be used for RF applications. The nanocomposite arrangement is unique showing a core double-shell structure of metal-carbon-polystyrene: M/C//P1/P2, where M = Co, Ni is the core material, C = graphene or carbon is the first shell acting as a protective layer against oxidation, P1 = pyrene-terminated polystyrene is the second shell for electrical insulation, and P2 = polystyrene is a supporting matrix (// indicates actual grafting). The nanocomposite formulation is briefly described, and the film deposition by spin-coating is detailed. Original spin-curves are reported and analyzed. One key outcome is the achievement of uniform and cohesive films at the wafer scale. Structural properties of films are thoroughly detailed, and weight and volume fractions of M/C are considered. Then, a comprehensive overview of DC magnetic and electrical properties is reported. A discussion follows on the magnetic softness of the nanocomposites vs. that of a single particle (theoretical) and the raw powder (experimental). Finally, unprecedented achievement of high magnetization (∼0.6 T) and ultra-high resistivity (∼1010 μΩ cm) is shown. High magnetization comes from the preservation of the existing protective shell C, with no significant degradation on the particle net-moment, and high electrical insulation is ensured by adequate grafting of the secondary shell P1. To conclude, the metal/polymer nanocomposites are situated in the landscape of soft ferromagnetic materials for RF applications (i.e., inductors and antennas), by means of two phase-diagrams, where they play a crucial role.

Anomalous Enhancement of the Magnetic Anisotropy of CoCrPt Alloy Thin Film With Ultrathin Pt Interface

An anomalous enhancement of the coercive field ( $H_{c}$ ) and of the perpendicular magnetic anisotropy (PMA) of CoCr10Pt10 (at.%) alloy thin films is observed when the magnetic layer is deposited on an ultrathin Pt interlayer (IL). The dc magnetic properties of Pt/CoCr10Pt10 are studied as a function of the magnetic alloy thickness (4–8 nm) and the Pt IL thickness (up to 3 nm). Both the coercive field and the interface anisotropy ( $K_{s}$ ) exhibit a non-monotonic dependence on the Pt thickness, showing a characteristic peak value at an intermediate thickness, with a rise in the PMA up to 25%. Similar thickness dependence of $H_{c}$ is observed when using Pd and Ir ILs, but with a more moderate enhancement. This approach provides a means to control and engineer the PMA of CoCrPt alloys, and may find an application in data storage and low-power spinelectronics.

A new family of [Cu(II)Ln(III)M(V)] heterotrimetallic complexes (Ln = La, Gd, Tb; M = Mo, W): model systems to probe exchange interactions and single-molecule magnet properties.

Four isostructural trinuclear 3d-4f-4(5)d heterotrimetallic complexes, with the general formula [L(2)CuLn(H2O)5(μ-NC)M(CN)7], were obtained from the association of binuclear 3d-4f complexes and {M(V)(CN)8}(3-) metalloligands (M = Mo, Ln = La ; M = W, Ln = La ; M = Mo, Ln = Gd ; M = Mo; Ln = Tb , where H2L(2) = 1,2-ethanediylbis(2-iminomethylene-6-methoxy-phenol)). The metalloligand coordinates through a single-cyanido group at the apical position of the copper(ii) ion belonging to the {Cu(II)Ln(III)} binuclear complex. The analysis of the magnetic data for the La(iii) derivatives (compounds and ), in the 1.85-300 K temperature range, shows a weak ferromagnetic exchange interaction between Cu(II) and Mo(V)/W(V) ions across the cyanido bridge (JCuM/kB = 3.6(6) K; g = 2.23(5) for and JCuM/kB = 3.8(6) K, g = 2.21(5) for , with H = -2JCuMSCu·SM). These results were used to simulate the magnetic properties of compound , using the isotropic spin Hamiltonian H = -2JCuMoSCu·SMo - 2JCuGdSCu·SGd. The resulting magnetic interaction between Cu(II) and Gd(III) ions via the phenoxo-bridge was found to be weakly ferromagnetic (JCuGd/kB = +4.5(2) K with JCuMo/kB = +3.6(2) K, gGd = gCu = 2.00 and gMo = 1.98). The dc magnetic properties for compound also show a predominant ferromagnetic interaction, while the ac magnetic measurements indicate the presence of the slow relaxation of the magnetization below 3.5 K.

Magnetic Properties and Morphology of Permalloy Prepared by the Compaction of the Powder

Permalloy is the name of nickel-iron alloys, which after heat treatment have an initial permeability much larger than that one of pure iron and are produced usually in the form of thin sheet [1]. Therefore it is logical to attempt to prepare such material in more "bulk" form, for example in the form of a cylinder or a ring, which would be more convenient for some industrial applications. The aim of this work was to investigate the influence of the powder size on ac and dc magnetic properties of the bulk samples prepared by a hot compaction of the powder.

Weak ferromagnetism and magnetoelectric effect in multiferroic xBa0.95Sr0.05TiO3–(1−x)BiFe0.9Gd0.1O3 relaxors

Multiferroic xBa0.95Sr0.05TiO3–(1−x)BiFe0.9Gd0.1O3 [xBST–(1−x)BFGO], where x=0.00−0.40, have been synthesized by the conventional solid-state reaction method. The crystalline phase, microstructure, relaxor behavior, ac conductivity, impedance spectroscopy, dc magnetic properties, complex initial permeability and magnetoelectric coefficient of these solid solutions have been investigated. The crystal structure is found to change from rhombohedral in BFGO rich compositions to cubic when x≥0.30. Room temperature dielectric properties are investigated within the frequency range from 1kHz to 1MHz and found to increase with BST content. The frequency dependence of high temperature dielectric measurements indicated that the composites with x≥0.20, exhibit relaxor ferroelectric behavior. The ac conductivity obeys the Jonscher’s universal power law and BST helps to enhance the electrical conductivity of the composites. Studies of impedance spectroscopy suggest that only grains have the contribution to the conductivity mechanism in this material. Magnetizations as a function of applied magnetic field measurements show weak ferromagnetism for 0.10≤x≤0.30 composites. The maximum value of remnant magnetization is found to be 0.565×103A/m (=0.08emu/g) for x=0.25 which is better than previously reported BaTiO3–BiFeO3 systems. The complex initial permeability is found to improve with the increase in BST concentration due to the reduction of oxygen vacancies. In addition, an enhanced magnetoelectric (ME) coupling is also observed and determined by the ME coefficient. The maximum value of ME coefficient is found to be 21.71×10−4V/A (=1.67mV/cmOe) for the x=0.25 composition. The BST–BFGO solid solutions show high-performance multiferroic properties and can be selected for further investigation.

Magnetization Reversal in PrCrO<sub>3</sub>

PrCrO3(PCO) samples were prepared by Citric acid route .The samples were characterized by XRD and SEM. The sample exhibits a single phase orthorhombic structure with Pbnm space group. The temperature dependent and field dependent magnetic measurements were measured in the range of 5K-400K at 100 Oe field and 0 to 5T field at 5K and RT respectively .The temperature dependence of dc magnetic properties show that the ZFC and FC magnetization curves are irreversible strongly and nearly symmetrical below 240K .There appears a novel magnetization behavior with negative magnetization characteristic in ZFC, the diamagnetism like behavior .This behavior exhibits the coexistence of canted anti-ferromagnetic and weak ferromagnetic phase and the existence of competition mechanism below 240K . This behavior can be interpreted from the interaction between Pr3+and Cr3+moments .The field and temperature dependent magnetization indicates the phase transition from canted anti ferromagnetic to paramagnetic occurred below 240K. In the region of higher temperature above 240K, PrCrO3behaved as a typical Curie-Weiss paramagnetic.Keywords: Orthochromites ,Multiferroics ,Neel temperature.PACS: 75.85 +t, 75.60 d, 75.50.Ee,75.30 Et,76.30 Kg

Magnetic Properties and Core Loss Behavior of Fe-6.5wt.%Si Ribbons Prepared by Melt Spinning

Fe-6.5wt.%Si alloy is prepared in the form of continuous ribbons with 25 mm in width and 0.03 mm in thickness by using melt spinning technique. The ribbons are flexible and could be wounded into tapes. DC magnetic properties and core loss behaviors of the ribbons after heat treatment are investigated in this paper. The magnetic properties are compared with ribbons by cold rolling and CVD methods. The melt spinning ribbons exhibit much less core loss in the frequencies more than 10 kHz. The melt spinning ribbons are promising to be used for electric devices used in medium or higher frequencies.