Magnetic Properties Of Nanocrystalline Fe73 Research Articles

The Effect of Inhibitors on the Structure and Magnetic Properties of Nanocrystalline Soft Magnetic Alloys

The present study examines the effect of various inhibitors on the structure and magnetic properties of nanocrystalline Fe73.5Cu1M3Si13.5B9 alloys, where M = Nb, W, Mo, V, Cr, or a combination of these elements. The introduction of inhibitors with higher solubilities in α-Fe results in an increase in the lattice parameter of the Fe3Si phase and induces a more marked drop in the initial permeability of the nanocrystalline alloy. A combination of several inhibitor elements is used and this allows an increase in the crystallization temperature and optimization of the core thermal treatment regime.

Magnetic properties and temperature stability of a molybdenum-doped finemet-type alloy

The influence of nanocrystallization conditions on the structure, magnetic properties, and temperature stability of nanocrystalline magnetically soft Fe73.5Cu1Nb1.5Mo1.5Si13.5B9 alloy is studied. It is found that preliminary low-temperature annealing exerts an influence on subsequent nanocrystallization of the alloy. In addition, preannealing followed by nanocrystallization considerably improves the magnetic properties of the alloy. It is shown that the magnetic properties of the material can be controlled by varying the frequency of a magnetic field used for thermal treatment causing nanocrystallization. It is established that the magnetic properties of nanocrystalline Fe73.5Cu1Nb1.5Mo1.5Si13.5B9 alloy offer a high temperature stability.

Effects of the Stress Annealing on Magnetic Properties of Nanocrystalline Fe<sub>73.5</sub>Cu<sub>1</sub>Nb<sub>3</sub>Si<sub>15.5</sub>B<sub>7</sub> Alloy

Magnetic properties of nanocrystalline Fe73.5Cu1Nb3Si15.5B7 ribbons with anisotropy induced by stress-annealing at different temperatures have been investigated.The results show that the magnetic properties were improved with the increase of temperature and excellent DC bias property was obtained after annealing above 580°C due to the transverse strip domain structure.

Crystallization kinetics and magnetic properties of Fe73.5Si13.5B9Cu1Nb1V2 nanocrystalline powder cores

Amorphous ribbons of the alloy Fe73.5Si13.5B9Cu1Nb1V2 were prepared by the standard single copper wheel melt spinning technique in the air atmosphere. The crystallization kinetics of amorphous ribbons was analyzed by non-isothermal differential scanning calorimetry (DSC) measurements. The crystallization activation energies of amorphous ribbons calculated by using Kissinger model were 364 and 337 kJ/mol for the first and the second crystallization, respectively. The Avrami exponent n was calculated from the Johnson-Mehl-Avrami (JMA) equation. The value of the Avrami exponent showed that the crystallization mechanism in the non-isothermal primary crystallization of amorphous ribbons was all shapes growing from small dimensions controlled by diffusion at decreasing nucleation rate. The variation of soft magnetic properties of nanocrystalline Fe73.5Si13.5B9Cu1Nb1V2 alloy powder cores as a function of milling times has been investigated. It is found that the effective permeability of the cores shows high frequency stability and decreases with the increase of milling times. The quality factor increases with increasing frequency in lower frequency range, and reaches a maximum at the frequency of 80 kHz then decreases gradually with increasing frequency.

Effects of Two-Step Annealing on the Magnetic Properties of Iron-Based Nanocrystalline Soft Magnetic Material

In the present paper, the effects of two-step annealing on the soft magnetic properties of nanocrystalline Fe73.5Cu1Nb3Si13.5B9 melt spun ribbons were studied. The two-step annealing comprises low-temperature preannealing (first step) for an α-Fe(Si) phase nucleation in an amorphous matrix, and a subsequent high-temperature annealing (second step) for the growth of precipitated crystallites. Compared with a nanocrystalline alloy obtained by conventional one-step annealing at 550 °C for 1 h, the grain size of α-Fe（Si）crystalline phase in the Fe73.5Cu1Nb3Si13.5B9 alloy decreased greatly after it is pre-annealed at 480°C for 1 h followed by annealing at 550°C for 40 min. It has been shown that the soft magnetic properties can be significantly improved by applying two-step annealing. The decrease of grain size of α-Fe(Si) crystalline phase may result from the nucleation rate increase during the crystallization of pre-annealed.

Magnetic properties of nanocrystalline Fe73.5Cu1Nb3Si15.5B7 alloy powder cores with different particle size prepared by rotor mill

The relationship between magnetic properties and particle size in nanocrystalline Fe 73.5 Cu 1 Nb 3 Si 15.5 B 7 alloy powder cores prepared by using a rotor mill and cold press was investigated. The powder cores having large particles of 250-850 pm exhibited stable permeability of 100 up to 500 kHz, a maximum level of 50 of quality factor at 50 kHz, and 360 mW/cm 3 core loss at 50 kHz and 0.1 T of induction. However the powder cores with small particles lower than 250 pm showed low permeability and high core loss as compared to large particle cores. Additionally the large particle cores have homogeneous and well-aligned microstructure leading to high density state. On the contrary, the powder cores composed of small magnetic particles showed irregular and complex distribution of magnetic powders, and the density seems rather low. The enhanced magnetic properties of powder cores with large particles were attributed to the particle size dependence of compressed state of powders.

Anisotropy in Nanocrystalline Fe73.5Cu1Nb3Si13.5B9 Wire

Soft magnetic properties of nanocrystalline Fe73.5Cu1Nb3Si13.5B9 wire have been investigated by magnetoimpedance ratio (MIR) and incremental permeability ratio (PR). The MI and PR measurements were carried out along the ribbon axis with longitudinal magnetic field. The MIR values increased drastically from 60% to 170% after proper thermal treatment. Annealing was performed in a vacuum for 1 h at various temperatures of 250, 350, 450, and 550 °C, respectively. Softest magnetic behavior has been observed in the samples annealed at 450 °C. Annealing over 550 °C leads to decrement of MIR and PR. The shapes of MIR and PR curves have shown the decrement of anisotropy field and also the PR curves have shown the change of anisotropy field from transverse to longitudinal direction as the annealing temperature increases.

Soft magnetic properties and structures of nanocrystalline Fe–Al–Si–B–Cu–Nb alloy ribbons

The effects of Al on the magnetic properties of nanocrystalline Fe73.5−XAlXSi13.5B9Cu1Nb3 alloy ribbons, where 0⩽X⩽10, are reported for the first time. The evolution of the structure and magnetic properties of the ribbons, which were initially cast into the amorphous state in an inert gas environment at subatmospheric pressure, were studied as a function of annealing temperature Tann. The minimum dc coercivity developed during annealing, Hcmin, was found to decrease significantly with increasing Al content from 0.5 A/m at X=0 to 0.3 A/m at X=2 and to remain at approximately this level over the range 2<X⩽8 before rising to 0.4 A/m at X=10. The saturation polarization, Js, was, however, found to decrease linearly over this range from Js=1.5 T at X=0 to Js=0.9 T at X=10 for samples exhibiting Hcmin. As there was little significant reduction in the mean crystallite size, dg, at Hcmin with increasing X, this decrease in coercivity was considered to result from a reduction of the magnetocrystalline anisotropy, K1, of the crystallites as a result of the incorporation of Al.

The effects of carbon on the magnetic properties of nanocrystalline Fe-based alloys

We investigate the magnetic properties of nanocrystalline Fe73.5Cu1M3Si13.5B9 (M=Nb or Mo) alloys when C is substituted for B up to 2 at%. It is found that the permeability and coercivity deteriorate with the content of C in the case of both M=Nb and Mo. The saturation magnetization also deteriorates as C is substituted for B in the case of M=Mo but it improves linearly with the C content in the case of M=Nb. This increase in the saturation magnetization of the Fe-Cu-Nb-Si-B alloy with C addition can provide an opportunity to overcome one of the main disadvantages, low magnetic flux density, of the alloy. In the latter part of the work we also investigate the magnetic properties of Fe76.5−yCu1Nby (Si0.5B0.4C0.1)22.5 (0≤y≤3) alloys, particular emphasis being given to the role of Nb in the presence of C. It is found that C may help Nb to suppress the growth of α-Fe grains in the alloy.

Effects of Al on the magnetic properties of nanocrystalline Fe73.5Cu1Nb3Si13.5B9 alloys

The effects of Al on the soft magnetic properties of nanocrystalline Fe73.5−xAlxCu1Nb3Si13.5B9 alloy ribbons are investigated in the composition range of 0≤x≤1.0. The relative initial permeability at 1 kHz is found to increase by the addition of Al, and reaches the peak value at x=0.1. The coercivity decreases, rather significantly, with the Al content in the whole composition range investigated in the present work, the values of the coercivity being 12.5 mOe at x=0 and 9.3 mOe at x=1.0. The magnetic induction at an applied field of 10 Oe, however, decreases moderately by the introduction of Al, possibly due to the dilution effect. The improvement in the soft magnetic properties is considered to result from the reduction in the grain size of the α Fe-Si solid solution phase of the Al-added alloy ribbons, which has been observed by transmission electron microscopy. Another factor may be due to the decrease in the intrinsic magnetocrystalline anisotropy K1 as Al is added to the alloy.