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1.
The Fe4 N pigments were prepared by nitridation of the Fe pigments in an ahnosphere of ammonia-hydrogen. The Fe pigments, the precursors, were prepared by reduction in hydrogen of the iron oxyhydrates having various particle sizes. The realtionship between the coercivity and the specific surface area of Fe4 N pigment was clarified. The relationship between the magnetic properties of the Fe pigments, the precursors, and those of the Fe4 N pigments was also clarified. The chemical stabilities of the Fe4 N pigment were also investigated. From the results of electron diffraction patterns, it is clear that the Fe4 N pigment particle maintains the original shape of the starting material aud that it consists of fine unit particles which link together to form a stereo-network structure, and that the unit particle is observed to be a single crystal, as in the case of the Fe pigment. 相似文献
2.
Mössbauer spectrum method was applied on tapes prepared using γ-Fe2 O3 , cobalt-epitaxial iron oxides and Fe particles to estimate the direction of orientation of the particles in the tapes. The coercivity and the squareness of the tapes was in the range of about 340 to 1140 Oe and 0.82 to 0.86, respectively. The γ-ray was applied to the tapes from the direction of the tape travel and the direction perpendicular to the tape plane. The angle of the orientation of the particles in the tapes was 29 -34 degree from the direction of the tape travel. The direction of magnetic moment in remanent state determined by Mössbauer method nearly agreed with that determined by hysteresis measurement. In the remanent state, the degree of discrepancy between the direction of orientation of particles and the direction of magnetic moment in particles increased with decreasing coercivity. It was considered that the magnetic moment in particles with lower coercivity tended to be inclined to the direction of tape plane. 相似文献
3.
Evaporation of Fe and Co at a residual O2 pressure of 10-5to 10-4Torr yielded magnetic films of high coercivities up to 500 Oe and magnetizations of about 1000 EMU/cm3. While the Co films were continuously deposited in the O2 atmosphere, a sandwich structure of Fe and Fe2 O3 was formed by intermittently altering the evaporation conditions. Both kinds of films were produced in the same geometrical arrangement. The Fe/Fe2 O3 films showed shape anisotropy caused by the oblique incidence deposition, while no uniaxial anisotropy was observed on the Co films. For both, Co films and Fe/Fe2 O3 sandwich films, it was possible to adjust the magnetic properties within a certain range. In both cases the coercivity increased considerably by annealing at 200°C. 相似文献
4.
Magnetic properties of iron nitride particles prepared with reactive gas evaporation method were investigated. Major products for higher NH3 gas pressure region is γ'Fe4 N and αFe. For lower pressure region αFe was produced, which was oxidized to Fe3 O4 after exposure to air. It is found that particles consist of γ'Fe4 N and γFe are more persistent to oxidation comparing to those of αFe. 相似文献
5.
Thin films of magnetic spinel iron oxides were prepared by pyrolysis of an ultrasonically generated aerosol of organometallic compounds. The bases of the method and experimental procedure are described. Polycrystalline films of good adherence and homogeneity were obtained. Lattice parameters were observed to be modified by film substrate strain interaction and to depend strongly on the hydrogen content. The oxidation state of iron was discussed in regard to the experimental growing conditions. Corresponding magnetic properties were investigated. Pure magnetite Fe3 O4 films withH_{c} = 400 Oe andM_{s} = 400 EMU/cm3and gamma ferric oxides films withH_{c} = 400 Oe andM_{s} = 250 EMU/cm3have been obtained without post deposition heat treatment. Annealing magnetite films in air resulted in a considerable increase of their coercivity (up to 800 Oe). 相似文献
6.
Amorphous video heads have been developed by a novel process of head fabrication. The process is simple and enables to fabricate the head with narrow track width(10-24μm) and narrow gap length(simeq0.2mu m). The heads are made of Fe4.7 Co70.3 Si15 B10 amorphous ribbon and have such a structure that the track width of the head is coincided with the thickness of an amorphous ribbon. Twin roller quenched ribbons are shown to be most suitable for the amorphous video head. Using these heads, the output signal for metal tape (Hc;1450 Oe, Br;2500G) is 14dB larger than the output for Cro2 tape(Hc;700 Oe, Br; 1500G) at 5MHz (3.45m/s relative speed). Furthermore, it is shown that the heads can record on the Hc; 1700 Oe metal tape effectively. 相似文献
7.
Oxidation kinetics and x-ray diffraction of the intermediate products have been investigated for several kinds of Fe3 O4 powders during the oxidation to γFe2 O3 . From these results, a two-components-hypothesis as an intermediate state of the Fe3 O4 - γFe2 O3 system is proposed, instead of a homogenious solid solution which has been widely recognized. The effect of the changes in particle size caused by the two phases oxidation products on the variations of magnetic coercivity was emphasised. 相似文献
8.
The recording characteristics of coated disks having high coercivity powder, in particular metal powder, are given. We manufactured various disks containing γ-Fe2 O3 (coercivity: 350 Oe), iron-cobalt metal powder (400 - 800 Oe) and iron metal powder (650 Oe), respectively. The recording characteristics of these disks were measured by using a Mn-Zn ferrite head whose saturation magnetization was 5,000 gauss. It was found that disks with higher coercivity showed a capacity for increased bit density, but at the same time, poor overwrite characteristics. The optimum coercivity proved to be about 650 Oe. The typical values for metal powder coated disks (650 Oe) were: critical bit density: 19,000 BPI reproduced output: 1 mV at 19,000 BPI overwrite: -30 dB. 相似文献
9.
The reproduce head flux function for a longitudinally, sinusoidally magnetized tape is calculated on the assumption that the tape first demagnetizes irreversibly and then remagnetizes reversibly. In contrast to previous work, wherein all changes were considered reversible, the present calculation leads to a nonvanishing loss at short wavelengths. The loss is, however, quite small for conventional γFe2 O3 tape, ranging from 4.5 dB to 8 dB for the cases of incontact reproduction with magnetic and nonmagnetic heads, respectively. It is concluded that little justification exists for the use of higher coercive force tape materials with the present values of tape remanence, and that tapes with the highest possible oxide packing fraction will always give the highest ouput. 相似文献
10.
Gee S.-H. Hong Y.-K. Jeffers F.J. Park M.-H. Sur J.C. Weatherspoon C. Nam I.T. 《IEEE transactions on magnetics》2005,41(11):4353-4355
Magnetic recording media requires good particle dispersion, a smooth surface, and small interparticle interaction to make an adequate signal-to-noise ratio (SNR). Well dispersed 50-60 nm sized spherical barium-strontium ferrite (S-Ba/Sr-Fe) nanoparticles were successfully prepared with 40 nm sized hematite precursor particles and BaCO/sub 3//SrCO/sub 3/ colloid. The coercivity and saturation magnetizations of S-Ba/Sr-Fe nano-particles were 1568 Oe and 48.6 emu/g, respectively. In order to evaluate magnetic interaction, magnetic tape was prepared using an Eiger mill with binder and organic solvent. /spl Delta/M measurement showed the S-Ba/Sr-Fe nanoparticles in the tape had negative magnetic particle-to-particle interaction. 相似文献
11.
The fabrication and read-write characteristics of a high-coercivity sputter-deposited maghemite (γ-Fe2 O3 ) thin-film disk medium is discussed. By employing a low sputtering gas pressure, severe internal strain is introduced into the films. This internal strain markedly increases coercivity. Furthermore, the films are composed of fine crystallites (300-400 Å in diameter), which result in extremely low media noise. A high coercivity (1060 Oe) γ- (Fe0.954 Co0.02 Ti0.02 Cu0.015 )2 O3 thin-film disk medium with a thickness of 0.095 μm exhibited superior read-write characteristics (e.g., a 2493 FRPM recording density D50 and a 42 dB signal-to-noise ratio). These results show that sputter-deposited maghemite films have a promising potential for use as high-density disk media. 相似文献
12.
Nb3Al AND Nb3(Al,Ge) tapes with excellent superconducting properties have been fabricated using high energy density laser beam irradiation, irradiations were carried out continuously on Nb-25at%AI and Nb-20at%Al -5at%Ge tapes prepared by powder metallurgical processing. With the high power density and short irradiation time, the tape could be heated and cooled much faster than a tape heat treated by conventional methods. The results were fine structure and large critical current density Jc values at high magnetic fields. Jc at 23 Tesla was over 104 A/cm2. This value was much greater than that obtained from a commercial Nb3Sn superconductor. New continuous irradiation systems have been developed for scale-up development. Nb3Al tapes 10 m in length were successfully fabricated. There was some scatter in Jc along the tape length. Small coil tests in magnetic fields indicated that the tape had excellent stability against a flux jump and mechanical strain. 相似文献
13.
The gadolinium garnet system {Gdz Y3-2x-z Ca2x } [Fe2-y Iny ] (Fe3-x Vx )O12 was investigated as a function of x, y, and z for0 leq x leq 0.6, 0 leq y leq 1.0 , and0 leq z leq 2.4 . The relationships between their compositions and magnetic properties were clarified. It was shown that some combinations of components in this system displayed improvements with respect to temperature stability (alpha = 0.05 %/°C-20 sim 60 deg C) and ferromagnetic resonance linewidth (ΔH = 20 ∼ 30 Oe) as compared with conventional garnets. 相似文献
14.
The magnetic properties and electromagnetic characteristics of Ba-ferrite tape for R-DAT magnetic contact duplication (MCD) were investigated. The tapes employed Ba-ferrite particles averaging 0.06 μm in diameter with an aspect ratio between 4 and 5. Ba-ferrite tapes were prepared with perpendicular, longitudinal, and no orientation, and their MCD and ring-head recording (RHR) characteristics were compared. Several distinctive characteristics were observed in MCD, and the desirability of perpendicular orientation at short wavelengths in MCD applications is clear. Tilted orientation was also investigated, and its output level was similar to that of perpendicular orientation in MCD, while in RHR it proved superior to perpendicular orientation in the short wavelength region. The magnetization mode of the slave tape was studied by waveform analysis using the FFT method and in conjunction with the tapes' magnetic properties, such as uniaxial anisotropy energy, remanence coercivity, and squareness ratio 相似文献
15.
《IEEE transactions on magnetics》1979,15(4):1146-1149
The magnetic properties and crystallization temperatures of alloys in the ternary Fe-B-Si system are reported. The Curie temperature increases slightly on replacement of boron by silicon. This results in a sharp ridge of relatively constant room-temperature saturation magnetization extending from Fe80 B20 to Fe82 B12 Si6 . The coercivity exhibits a broad minimum, both before and after stress relief annealing, in the region around Fe81 B15 Si4 and extending at least to Fe77 B13 Si10 . The crystallization temperature increases with increasing silicon and with decreasing iron and boron. The alloys with silicon are generally easier to prepare in the amorphous state than the binary Fe-B alloys. Thus for the highest saturation magnetization alloy combined with ease of preparation, stability, and lowest losses, the alloys between Fe81 B17 Si2 and Fe82 B12 Si6 are preferred. 相似文献
16.
Guohong Mu Xifeng Pan Na Chen Keke Gan Mingyuan Gu 《Materials Research Bulletin》2008,43(6):1369-1375
The barium hexaferrite nanorods were successfully prepared by sol–gel technique combined with polymethylmethacrylate as template. The crystal structure, morphology and magnetic properties of BaFe12O19 with different shape were investigated with X-ray diffraction, field emission scanning electron microscope and vibrating sample magnetometry. The results show that diameters and lengths of magnetic nanorods are about 60 nm and 300 nm, respectively. The coercivity of rod-shaped BaFe12O19 is increased to 5350 Oe, in comparison with 4800 Oe with plate-shape. The formation mechanism of BaFe12O19 nanorods and reasons resulting in high coercivity are discussed. 相似文献
17.
Mn-Al thin films with the composition of 31-68 at.% Mn were prepared by rf magnetron sputtering at various substrate temperatures then annealed in vacuum. Effects of the chemical composition, substrate temperature and annealing temperature on the magnetic properties of Mn-Al films have been investigated. The analysis of X-ray diffraction and magnetic measurement indicate that τ-phase was synthesized at a composition range of 40-60 at.% Mn. However, the formation of large amount of τ-phase occurred for Mn50-Al50 films, which have a high coercivity up to about 3000 Oe and a fairly large saturation magnetization of about 420 emu/cc 相似文献
18.
Bendaoud R. Tailhades P. Fert A. Bertrand D. Redoules J. Rousset A. 《IEEE transactions on magnetics》1987,23(6):3869-3873
New manganese defect metastable ferrites with spinal structure were prepared by oxidation at a temperature lower than 500°C of submicron manganese substituted magnetites, Fe3-x MNx O4 (0 leq x < 1 ). X-ray diffraction measurements and thermal analysis studies have been carried out on these systems. Low-temperature magnetic measurements have also been carried out. With these studies, it has been possible to depict the cation distribution in substituted magnetites and oxidized compounds, and to understand the complex process of oxidation. In defect spinels, vacancies are formed not only from oxidation of Fe2+ions, but also of Mn2+and Mn3+ions. Manganese-rich compound with x = 0.97 having high content of Mn3+and Mn4+ions show an important increase in coercive force, which exceeds 700 Oe at 4.2 K. 相似文献
19.
Ash K.P. Wachenschwanz D. Brucker C. Olson J. Trcka M. Jagielinski T. 《IEEE transactions on magnetics》1990,26(6):2960-2965
A multilayered magnetic head that can read and write at 150 MHz on metal particle tape with a coercivity of 120 kA/m (1500 Oe) has been developed. Ten 2-μm layers of Fe68Ru8Ga7 Si17 alloy, with 100 nm of SiO2 used as spacer, form the magnetic-core thickness and the track width. The head was tested in a rotary recording system at a relative head-to-tape speed of 73 m/s. At a linear density of 4000 fc/mm (100 kfc) and 150 MHz, the measured single frequency signal to 300-kHz-slot noise was 33 dB (RMS-RMS). The measured frequency response curve agrees with theory and indicates a head-to-tape spacing of 70 nm at high speed. The read efficiency of the head decreases from 37% at low frequency to 15% at 150 MHz 相似文献
20.
H. J. Lim J. G. Byrne M. S. Chae M. B. Maple 《Materials and Manufacturing Processes》1997,12(2):261-274
High-Tc BSCCO superconductor tapes were prepared by the conventional powder-in-tube method. Some tapes involved partial melting, while the others involved solid-state processing only. Bulk samples were prepared by powder metallurgy. X-ray diffraction (XRD) showed the presence of both BSCCO 2223 (Tc = 105 K) and BSCCO 2212 (Tc = 80 K) phases in all the materials. For the mostly BSCCO 2212 phase samples, x-ray studies indicated that tape #1 which involved partial melting at 850°C for 0.3 h had a higher degree of basal orientation than either a tape #2 sample which involved partial melting at 855°C for 0.5 h, or a bulk (#2) sample. For the mostly BSCCO 2223 phase samples, however, a comparison of bulk (#1.), tape #3 (solid state processing at 840°C) and tape #4 (partial melting at 865°C for 0.5 h) samples, showed that the solid-state processed tape (#3) had the highest degree of basal orientation. Direct current magnetic susceptibility measurements were used to follow the transition at Tc. Critical current density, Jc, values were estimated from DC magnetic hysteresis loops for all bulk and tape samples. 相似文献