Microstructures and soft magnetic properties of Fe80P20-xSix (x = 4.5–6.5) amorphous ribbons

Fe-based amorphous ribbons with excellent soft magnetic properties and mechanical properties were prepared in the Fe–Si–P ternary system. Enhanced soft magnetic properties could be achieved through annealing treatment of the ribbons for 1 h at 325 °C, which is far below the glass transition temperatures (462–474 °C). Icosahedral medium-range ordering with a size range of around 2 nm occurred throughout the amorphous matrix during the low-temperature annealing treatment. The annealed ribbons exhibited improved magnetic saturation of over 185 emu/g while maintaining good mechanical flexibility. During icosahedral ordering, the distance between the Fe atoms and the coordination number within the amorphous ribbon can be optimised for achieving high magnetic saturation. However, nanocrystallisation of the SiP and Fe₂P transition phases embedded within the amorphous matrix occurred after the annealing treatment for 1 h at 385 °C, which caused deterioration of the soft magnetic properties and mechanical flexibility of the ribbons. Therefore, the combination of high magnetic saturation and mechanical flexibility of the amorphous ribbons could be optimised through low-temperature annealing treatment without any nanocrystallisation.     

Structure and magnetic properties of Fe96−x Zr x B4 nanowire arrays

Fe96-xZrx B4(1相似文献   

Effect of nanoparticles on the magnetic properties of Mn–Zn soft ferrite

In this paper, the effect of nanostructures on the magnetic properties like the specific saturation magnetization (σ_S) and the coercivity (H_C) for Mn_0.4Zn_0.6Fe₂O₄ ferrite prepared by the co-precipitation method has been presented. We have shown by means of X-ray diffraction that the resulting ferrite is made up of nanoparticles, and that the average size of these nanoparticles calculated with the Scherrer formula depends upon the sintering temperature. When the sintering temperature is increased from 500 to 900 °C, the average nanoparticle diameter varies from 19.3 to 36.4 nm. The nanoparticle phase is further confirmed by scanning electron microscopy (SEM). Both results are found to be in good agreement. The magnetic properties are explained on the basis of the single-domain and multi-domain theory.     

Magnetic properties of U (Fe x Al1−x )2 and U(Fe y Ni1−y )2 compounds

The results of magnetic measurements and ferromagnetic resonance studies performed on U(Fe _x Al_1–x )₂ and U(Fe _y Ni_1–y )₂ compounds over a large temperature range are reported. The saturation magnetization decreases nearly linearly when substituting Fe by Al or Ni. In the composition range x<0.84 and y<0.81, the compounds are Pauli paramagnets, except in the region with y0.10. For UNi₂ two types of magnetic behaviours are shown. This compound can be both a ferromagnet withT _c =23.5 K and a Pauli paramagnet, depending on the crystal structure. Above the Curie temperatures, the reciprocal susceptibility for the compounds with x>0.84 and y>0.81 obeys a temperature dependence of the formX=X _o+C(T-) ^–1. The effective iron moments decrease when substituting iron by nickel or aluminium. The ferromagnetic resonance measurements show that theg values are not composition-dependent. A linear variation of the mean iron magnetization with the exchange field is observed. Finally, the magnetic behaviour of iron in these compounds is analysed.     

Influence of structurization of amorphous metallic alloys Al87Y5 − x Gd x Ni8 − y (x = 0, 1, 5; y = 0, 4) on their mechanical properties

Amorphous metallic alloys (AMAs) Al₈₇Y₅Ni₈, Al₈₇Gd₅Ni₈, Al₈₇Y₄Gd₁Ni₈, Al₈₇Y₄Gd1Ni₄Fe₄, and Al₈₇Gd₅Ni₄Fe₄ produced by melt spinning on a cooled substrate have been studied. Based on the data of differential scanning calorimetry and X-ray diffraction, the activation energies of individual stages of crystal-lization, the sizes and volume fractions of nanocrystals in an amorphous matrix have been calculated. The alloying of AMAs with Y or Gd is shown to lead to the formation of particles with sizes of 9–15 nm at the first stage of nanocrystallization, which provides their high microhardness.     

Morphology and magnetic properties of Fe x Co1−x /Co y Fe3−y O4 nanocomposites prepared by surfactants-assisted-hydrothermal process

Recently, we have demonstrated the successful synthesis of Fe _x Co_1−x /Co _y Fe_3−y O₄ nanocomposites with various alkaline solutions by using surfactants-assisted-hydrothermal (SAH) process. In this article, the synthesis of Fe _x Co_1−x /Co_yFe_3−y O₄ nanocomposites with their sizes varying between 20 nm and 2 μm was reported. X-ray powder diffraction (XRD) analyses showed that the surfactants, pH, precipitator, and temperature of the system play important roles in the nucleation and growth processes. The magnetic properties tested by vibrating sample magnetometer (VSM) at room temperature exhibit ferromagnetic behavior of the nanocomposites. These Fe _x Co_1−x /Co _y Fe_3−y O₄ nanocomposites may have a potential application as magnetic carriers for drug targeting because of their excellent soft-magnetic properties.     

Correlation between the magnetic and electrical properties of the (VS)x(Fe2O3)2−x oxysulfide system

The correlation between the magnetic and electrical properties of the (VS)_x(Fe₂O₃)_2?x (0.9<x<1.25) oxysulfide solid solutions has been studied. The crossover of conductivity from the semimetallic to semiconducting type is accompanied by changes in the magnetic susceptibility, which are characteristic of the transition from delocalized to localized electrons. For x=1.25, a region of the ferromagnetic ordering has been established in the temperature range 90–120 K.     

Effect of composition on texture and magnetic the crystallographic properties of the Sm（Co,Fe,Cu,Zr）z ribbons prepared by simple processing

Sm(Co_balFe_yCu_xZr_w)_z ribbons have been prepared by melt spinning at a low wheel velocity followed by short-time aging and slow cooling the as-spun ribbons from 850 to 400℃. It is found that the composition can significantly influence the degree of crystallographic texture of the ribbons. The 1:7 phase of the as-spun ribbons is segregated into 1:5 and 2:17 phases by the simple processing procedure. However, the crystallographic texture is still preserved in the ribbons after precipitation hardening. (BH)_{\rm max} about 86kJ/m^{3} can be obtained in the Sm(Co, Fe, Cu, Zr)_{z} ribbons by the adjustment of composition.     

A mean-field study on the thermo-magnetic properties of GdxCo1−x amorphous alloys (0.16⩽x⩽0.25)

We present a mean-field study on the thermo-magnetic properties of Gd_xCo_1−x amorphous alloys in the 0.16⩽x⩽0.25 composition range. A single set of exchange integrals and fixed values of the angular momenta of Gd and Co fairly describe the temperature dependence of magnetization. The magnetic specific heat and magnetic entropy show field and composition dependence. Both the specific heat anomaly and the saturated entropy, at the temperature of the magnetic phase transition, increase with increasing Co concentration. The two magnetic subnetworks and their cross-interactions contribute differently to the specific heat.     

Research on the magnetic properties and crystal lattice aberrance of melt-spun Nd9Fe85−xMnxB6 (x=0–1)

Magnetic properties and crystal lattice aberrance of melt-spun Nd₉Fe_85−xMn_xB₆ (x=0,0.5,1) nanocomposite materials were investigated by DTA, XRD, EXAFS and VSM. It was found that a certain amount of manganese added to Nd₉Fe₈₅B₆ magnets can promote crystal and enhances the hard magnetic properties. The coercivity and remanence ratio increases from 4.3 kOe and 0.70 to 5.0 kOe and 0.72, respectively. The remain magnetization has not distinct reduce under the optimum annealing method. M–T shows Mn doping decreases the Curie temperature of the Nd₂Fe₁₄B phase and raises that of α-Fe phase. The origin for the enhancement of magnetic properties is not only related to the reduction of grain size which enhances the exchange coupling between grains but also to the precise crystal structure.     

Effect of Dy-Co on physical and magnetic properties of X-type hexaferrites (Ba2−xDyxCu2Fe28−yCoyO46)

Sol–gel method is used to make a sequence of Barium based “X-type hexagonal ferrite (X-HF)” Ba_2−xDy_xCu₂Fe_28 −yCo_yO₄₆. “X-type hexagonal ferrites” with concentrations of “x = 0.0, 0.02, 0.06, 0.1 and y = 0.0, 0.1, 0.3, 0.5” are taken and the substitution impact of trivalent Dy³⁺ and divalent Co²⁺ is observed on the physical and magnetic properties of X-HFs. The XRD result, the refinement of which is accomplished using CelRef software validates the existence of pure single phase in these ferrites. Morphological structure of the crystal grains is calculated using electron microscopy and it is found that the grain has varying size in the range of 0.75–1.001 mm. FTIR analysis is done with and without the sintering process to examine the changes relevant to the structure and the chemistry of the material and the phases existed in the material. Thermogravimetric analyzer is used to measure the TGA and DSC quantities. All FTIR, DSC, and TGA results show that they are in good harmony with the results outcomes from XRD. “Vibrating sample magnetometer (VSM)” is used to quantify the magnetic properties of the sample under observation. It is observed that with an increase in the concentration of Dy-Co, M_r (Remanence) value decreases this could be reasoned by spin canting effect. The value of coercivity (H_c) changes from 317 to 158 G which follows the inverse relation between grain size and coercivity. The future use of the material may be in the microwave absorption devices.     

Effect of Nd doping on the magnetic properties of charge-ordered Bi0.6−x Nd x Ca0.4MnO3 (0.0≤x≤0.6) perovskite manganites

We have studied structure, magnetic and transport properties of polycrystalline Bi_0.6?x Nd _x Ca_0.4MnO₃ (x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6). Substitution of Nd at Bi sites induces a strong interplay between the magnetic and charge ordering. The charge-ordering temperature (T _CO) decreases with increasing x. Further, the antiferromagnetic ordering temperature (T _N) increases sharply at both extremes and remains nearly constant for x=0.2–0.4. At T<T _N a transition to a metamagnetic glass-like state is also seen. Nd doping also leads to enhancement in the magnetic moment and a concomitant decrease in resistivity up to x=0.3 and then an increase in resistivity up to x=0.5. Furthermore, Nd doping promotes an antiferromagnetic to ferromagnetic type fluctuation in the materials at room temperature, as evidenced by the change in the value of the paramagnetic Curie temperature. We find that the local lattice distortion induced by the size mismatch between the A-site cations and the 6s² character of Bi³⁺ lone pair electrons explains the observed peculiarity in magnetic and transport properties of Nd-doped Bi_0.6Ca_0.4MnO₃.     

The influence of the local surrounding on the hyperfine interactions in Zr(Fe1−x Ni x )2 compounds

Mössbauer spectroscopy and the TDPAC method have been used to study Zr(Fe_1–x Ni _x )₂ compounds forx0.30. The hyperfine magnetic field at the Fe sites and the quadrupole splitting as functions of nickel concentration were analysed by use of⁵⁷Fe Mössbauer spectroscopy. Values of the internal magnetic field on¹⁸¹Ta nuclei have been found by means of the TDPAC method.     

Low-temperature properties of amorphous (Mo1−x Ru x )0.8P0.2 alloys

Amorphous (Mo_1–x Ru _x )_0.8P_0.2 alloys (0.3x0.7) have been investigated with measurements of the specific heatC and thermal conductivity . Also the superconducting properties (critical temperatureT _c and upper critical field) have been determined. Well belowT _c , all alloys show the familiar behavior known for glasses, i.e.CT ⁿ and T _m withn1 andm2 which is attributed to tunneling states (TLS). The largeT _c allows an unambiguous determination of the coefficients ofC and . Compairing our data with literature data, we find no correlation between the TLS density of states and the glass temperature or crystallization temperature, as opposed to insulating glasses where such a correlation appears to exist. The unusual annealing behavior found previously in amorphous Zr–Ni and Zr–Cu, which was attributed to a change in the TLS relaxation-time spectrum, is confirmed in the present work.     

Effect of Co 2 + content on the magnetic properties of Co x Fe 3 − x O 4 /SiO 2 nanocomposites

Non-stoichiometric Co_xFe_3???xO₄/SiO₂ (x = 0.8, 0.9, 1.0, 1.1) nanocomposites have been prepared by sol-gel method. The structure, morphology and magnetic properties of the obtained samples were characterized by X-ray diffraction, transmission electron microscopy, vibrating sample magnetometer and Mössbauer spectroscopy at room temperature. As the Co^2?+? content increases, the average particle size of the spherical Co_xFe_3???xO₄ in the samples decreases and the lattice constants increases. The hyperfine fields for both A- and B-site decrease, while the fraction of Co^2?+? occupying the A-site increases. Magnetization measurements show the saturation magnetization and coercivity of Co_xFe_3???xO₄/SiO₂ decrease with increasing Co^2?+? content. The decrease in magnetization results from the weakened A-B interactions between Fe^3?+?, and the change in coercivity can be related to the variation of Co^2?+? at B-site and the decreasing particle size.     

Photoluminescence properties of heavily doped heterostructures based on (Al x Ga1 − x As)1 − y Si y solid solutions

It has been established that the photoluminescence spectra of heavily doped heterostructures based on Al _x Ga_{1 ? x} As)_{1 ? y} Si _y solid solutions exhibit quenching of the main exciton bands of Al _x Ga_{1 ? x} As ternary solid solutions and appearance of other maxima. The quenching of the main exciton bands can be associated both with the DX-center formation and with the change in the character of the band structure of (Al _x Ga_{1 ? x} As)_{1 ? y} Si _y quaternary solid solutions.     

Effect of film thickness on the electromagnetic properties of La1−x Sr x MnO3 coatings

Coatings of La_1?x Sr _x MnO₃ (x = 0.225) with thicknesses of 6 and 1000 nm are deposited by magnetron sputtering on LaAlO₃ substrates and the electromagnetic properties of obtained films are studied in detail. It is found that the colossal magnetoresistance observed in the samples is considerably influenced by interface effects.     

Impact of iron composition on the calculated electronic and magnetic properties of Fe3−xNixSi

ABSTRACT

The structural, electronic and magnetic properties of Fe_3?xNi_xSi alloys with variable iron composition (0?≤?x?≤?1) have been investigated within by using Projector augmented wave (PAW) method. The exchange–correlation potential was treated with the generalised gradient approximation (GGA) for the calculation of the structural properties and for the computation of the electronic and magnetic properties in order to treat the d states. These alloys crystallize in cubic Heusler structures; The Fe₃Si and Fe₂NiSi have a regular structure DO₃ and L2₁ respectively. To describe the experimental proprieties we use the on-site Coulomb interactions of U_eff(Ni)?=?3.1?eV and U_eff(Fe)?=?3.4?eV. A good agreement between calculated and experimental magnetic moments is found for the cubic Heusler phases without the addition of Hubbard-model. The obtained results of the density of states and the spin-polarized band structure show that the Fe₂NiSi alloy has half-metallic property. Through the obtained values of the total spin magnetic moment, we conclude that in general, the Fe₂NiSi alloy is half-metallic ferromagnet material whereas the Fe₃Si alloy has a metallic nature.