Au-Fe-Ni permanent magnet alloys

A gold permanent magnet for an ornamental material is developed in the Au-Fe-Ni system. It is found that the magnetic properties of the An-12.5 wt% Fe-12.5 wt% Ni alloy aged at 450°C for seven hours and cold-swaged by 92 percent are Br = 0.53 T (5300 G), iHc = 40.8 kA/m (510 Oe), and (BH)max = 9.1 kJ/m³(1.1 MGOe). The Au-12.5 wt% Fe-10 wt% Ni-2.5 wt% Co alloy aged at 450°C for 2.5 h and swaged by 86 percent attained Br = 0.54 T (5400 G), iHc = 42.4 kA/m (530 Oe), and (BH)max = 9.6 kJ/m3(1.2 MGOe). In these alloys, the magnetic hardening is due to the fine Fe-Ni rich ferromagnetic particles precipitated in the Au matrix.     

Low cobalt Fe-Co-W semihard magnetic alloys for remanent reed switch applications

Semihard magnetic alloys of Fe-Co-W have been developed for application in remanent reed switches. These alloys are very ductile and can be processed into fine wires. The 78%Fe-12%Co- 10%W alloy shows the magnetic properties: Br= 19.2 kG, Br/B200= 0.95, and Hc= 25 Oe. These magnetic properties are superior to those of the commercially used Remendur (49%Co-48%Fe-3%V) or Nibcolloy (85%Co-12%Fe-3%Nb), and the alloy itself consists of a much less expensive cobalt content than those alloys. This 78%Fe-12%Co-10%W alloy is flattenable into reeds, plateable with contact materials, and sealable in glass vials without losing its magnetic properties. Fe-Co-W alloys are adequate for use in remanent reed switches and present distinct advantages from the aspects of their inexpensiveness and superior characteristics.     

New longitudinal recording media CoxNiyCrzfrom high rate static magnetron sputtering system

Three new magnetic alloys A:Co64.2Ni27.4Cr8.4. B:Co74.1Ni15.9Cr10.0, and C:Co82Ni18were used as targets to sputter thin films with coercivities up to 1015 Oe, 926 Oe, and 825 Oe respectively. Chromium films were used as the base layer. With a base pressure below 2 × 10^-7torr and chromium thickness of 2500Å, the following magnetic characteristics of alloys A and B were obtained: Hc>900 Oe, Brδ>530 G-µm, S>78%, S* > 93%, S/N (at 5MHz) > 45dB and D50> 17KBPI. X-ray diffraction measurements indicate the (1011) texture of CoNiCr films is the reason for the high coercivity and squareness ratio. This orientation may result because the in-plane atom density for Co alloys HCP(1011) and Cr BCC     

The development of <100> texture in Fe-Cr-Co-Mo permanentmagnet alloys

The cold-rolled and recrystallization textures of Fe-Cr-Co-Mo permanent magnet alloys are described. The studied composition is Fe-30%Cr-15%Co-3%Mo (in wt.%). The cold-rolled texture can be considered to be {111}<110>, {111}<112>, {100}<110>, and {211}<110>, while the recrystallization texture can be considered to be {111}<100>, {110}<112>, {211}<110>, and {110}<110>. The secondary recrystallization is caused by heat-treating the alloys in the sequence of α, α+γ, α+γ+σ, α phase region. This results in a favorable texture of {110}<110> and <100> direction, aligning along the transverse direction (TD) of the strips. The best magnetic properties obtained in this study were 1.2 T (12.0 kG), iH _c=82.0 kAm^-1 (1025 Oe), and (BH)max= 60.8 kJm^-3 (7.6 MGOe) with TD alloys     

Simultaneous substitution of Co2+and Zn2+ions in submicronic acicular γ - Fe2O3particles

In iron sesquioxide of acicular shaded γ-Fe2O3simultaneous substitution of Co²⁺and Zn²⁺ions leads to the formation of mixed-defect ferrites and modulation of magnetic properties is of interest for their application to high density magnetic recording. It is shown that the coercive force, remanent magnetization and saturation-magnetization are controlled by a judicious choice of the contents of Co²⁺and Zn²⁺, while it is indispensable to optimize the morphological features like the average size of the crystallites, the shape, the size and texture of the particles. A high value of coercive force (650-700 Oe) and of the remanent magnetization (35-45 emu/g) had been obtained with a minimal content of cobalt ions (Co²⁺= 2.5 to 3% by wt.) permitting limits to the magnetocrystalline anisotropy of these compounds and their thermal variation near the ambient temperature. The influence of the zinc content had been systematically studied notably in relation to its effect on the structural, morphological and magnetic properties of the ferrites.     

Ferro-antiferromagnetic transition in the alloy system Fe65(Ni1-xCrx)35at low temperatures

The magnetic and electric properties of iron-nickel "invar" alloys and stainless steels are measured at low temperatures. It is shown that "invar" alloys such as stainless steels exhibit one-directional anisotropy, and their electric and galvanomagnetic properties are rather specific. It is shown also that the concentration dependence of Neel temperatures and magnetoresistance for the systems Fe-Ni and Fe65(Ni1-xCrx)35are similar.     

A new magnetic alloy of high constant permeability

Several conventional alloys of constant permeability used previously were of lower values of permeability, or they would change obviously in different intensities of magnetic field and thus could not satisfy some specific requirements of electrical application. The alloys consisted of Ni 60-70 wt%, Fe 29-39wt% and Mn 0-1 wt% were investigated. The best of those alloys for certain use is 1J66 alloy in China. It is a new alloy of high constant permeability with the chemical composition as Fe 34 wt%, Ni 65 wt% and Mn 1 wt%. Its AC induction permeabilitymu_{L}= 3400G/Oe (f=60Hz). Within the range of Bm=20-6800 G, the stability of AC induction permeability (f=60Hz)alpha_{sim} = 4.3%. The α is defined asalpha = mumax-mumin/mumin,alphamaxandmuminare the maximum and the minimum of permeability respectively in the range of given magnetic field. The temperature stability αTof μLwithin the range of temperature from -60°C to +90°C is 2.9%. The saturation magnetic induction of 1J66 alloy equals 13500 G. The remanenceB_{r} < 150G. The coercive forceH_{c} = 0.05Oe. The oxygen content of 0.015- 0.04% in the alloy is considered necessary for obtaining a good stability of permeability.     

Preparation and magnetic properties of barium hexaferrite nanorods

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.     

A new permanent magnet material: Modified Ca ferrite

An experiment was carried out to investigate the preparation condition of anisotropic Ca system ferrite magnets with optimum magnetic and physical properties. Compositions were chosen according to the formula (CaO.nFe2O3)100-x(La2O3)x, wherexwas varied between 0 and 4.0, and n between 5.5 and 6.25. The optimum condition of making magnets and some properties of a typical specimen are as follows. The preparation condition: composition (CaO.6Fe2O3)97(La2O3)3, semisintering condition 1250°C × 1 h in O2gas, sintering condition 1275°C × 0.5 h in O2gas. Magnetic properties:4piI_{10}k = 4200G, 4πIr = 4100 G,IHC= 2100 Oe,BHC= 2050 Oe,(BH)_{max} = 3.5MG . Oe, Ku = 3.34 × 10⁶erg/cc, HA= 20.5 kOe,sigma_{s} = 64.8emu/g, Tc = 446°C.     

Low-cobalt Cr-Co-Fe magnet alloys obtained by slow cooling under magnetic field

The permanent magnet properties of magnetic field aged Cr-Co-Fe alloys containing 5-9 weight percent (wt %) Co were investigated. By slow cooling from above the spinodal temperature under applied magnetic field, energy products of (BH)max= 4-6 MG . Oe were obtained. The effects of cobalt content, cooling rate, and applied magnetic field strength were studied.     

Uniaxial anisotropy by "radiomagnetic" treatment; controlling factors in a new process

A new process-an electron-"radiomagnetic" treatment-for obtaining high-remanence, low-coercive-force loops in magnetic alloys was recently announced. As an example, 2-MeV electron irradiation of 6-mil-thick ring laminations of polycrystalline 5-80 Mo Permalloy with 10¹⁷e/cm²in an applied circumferential magnetic field of 0.2 Oe atsim100degC produced record highs in remanence (∼6700 G) for this material. Additional studies of this process have been made to determine some of the controlling factors and the range of application. In particular, the effects of the dose (number of e/cm²) and of the preirradiation magnetic properties were examined. The results show that: 1) for a given dose of1.1 times 10^{17}2-MeV e/cm², the relative change in remanence (DeltaB_{r}/B_{r}) is always positive, ranging from 10 to 50 percent, but varies inversely with the preirradiation value of remanence (Br); 2) for the same dose, the relative change in coercive force (DeltaH_{c}/H_{c}) also depends upon the preirradiation value of remanence, but in a different way. ForB_{r} < 5000G,DeltaH_{c}/H_{c}is either negative or zero. ForB_{r} > 5000G,DeltaH_{c}/H_{c}is positive, ranging from 20 to 150 percent, and increases linearly withB_{r}; 3) if the dose is reduced tosim0.8 times 10^{17}e/cm², thenDeltaH_{c}/H_{c}is reduced to a tolerable level (∼10 percent) with no significant sacrifice in the positive gain in remanence and rectangularity. Hence, there are optimum dose ranges in the "radio-magnetic" treatments of alloys, where significant gains in remanence may be obtained without appreciable increases in coercive force.     

Directional solidification of Co-Cu-R permanent-magnet alloys

Co-Fe-Cu-Ce permanent-magnet alloys have been prepared by directional solidification using a modified Bridgman technique. Samples melted at low superheat temperatures (DeltaT sim 20degC above the melting point of about 1100°C) and solidified at moderate rates (∼2.3 cm/h) resulted in a reasonably homogeneous columnar grain structure with a preferred crystallographic orientation. Thecaxis is generally aligned within 15° of the growth axis. Increasing the speed of solidification led to a fine-grained structure with no texture, while decreasing the speed led to coarse columnar grains with erratic orientation. A large superheat temperature (DeltaT sim 300-400degC resulted in a reaction of the liquid with the alumina crucible wall and led to the formation of face-centered cubic Co-rich dendrites. With the modified Bridgman technique, oriented samples 8 cm long and 2.54 cm in diameter have been prepared with good magnetic properties. After annealing at 1000°C followed by aging at 400°C, a Co3.5Fe0.5CuCe alloy exhibited values ofiHc= 7000 Oe, Br= 6100 G, and(BH)_{max} = 9.2MG.Oe. A Co3.6Fe0.5Cu0.9Ce alloy exhibited values ofiHc= 6000 Oe,B_{r} = 6250G, aud(BH)_{max} = 9.5MG.Oe after similar treatment.     

Preparation of coated iron powders by chemical plating

Small iron particles can be produced by reduction of γ-Fe2O3and α-FeOOH with hydrogen; they show outstanding magnetic properties and can be used for recording media. The main difficulty concerns the tendency of these particles to oxidize. We have studied a preparation process in two steps: a) reduction of iron oxides or oxy-hydroxides; b) chemical plating in the same furnace. The magnetic properties of the iron powders chiefly depend on the reduction step. The water content in the gas leaving the furnace has been shown to be the main parameter determining the obtainment of powders with high magnetic properties. The iron powders, which were pyrophoric, have been quenched in chemical plating bath of suitable formulation and coated with cobalt or copper. Typical magnetic properties are: saturation magnetization σsat= 130-165 emu/g, intrinsic coercivityjHc= 350-450 Oe; best magnetic properties: σsat=155 emu/g,jHc=700 Oe. The coated powders have been submitted to heat treatment in air saturated with water, showing a good resistance to oxidation.     

Magnetic properties of polycrystalline gadolinium calcium vanadium and indium substituted YIG

The gadolinium garnet system {GdzY3-2x-zCa2x} [Fe2-yIny] (Fe3-xVx)O12was 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 degC) and ferromagnetic resonance linewidth (ΔH = 20 ∼ 30 Oe) as compared with conventional garnets.     

Electron Concentration Dependence of Phase Transition and Magnetic Properties in NiMnGa Alloys

The phase transition, Curie temperature and magnetic properties of NiMnGa alloys represented by S1, S2, S3, and S4 in different atomic percentage were investigated from TG/DTA and PPMS measurements. It was found that the electron concentration (e/a) ratio of S1 and S4 as well as S2 and S3 are equal to each other. The transformation temperatures and magnetization values are similar for these alloys having the same e/a. Results show that room temperature magnetization depends on valence electron concentration of alloys and saturation of alloys increases with the decrease of e/a ratio. The measured coercivity values for all alloys were above 125 Oe and they had a long saturation field, i.e., above 10000 Oe, by exhibiting, the characteristics of hard magnetic materials.     

Si含量对纳米晶Fe_(87-x)Cu_1Nb_3Si_xB_9合金磁性能的影响

研究了Si含量对Fe87-xCu1Nb3SixB9合金经不同方式退火后磁性能的影响。结果表明:随Si含量的增加,Fe87-xCu1Nb3SixB9合金经普通退火后软磁性能逐渐得到优化;经磁退火后可感生出单轴磁各向异性,且磁退火特征随Si含量的增加而逐渐明显。根据横磁退火实验结果计算出的感生磁各向异性值Ku,则由26.7J/m3(Si=9.5at%)降低至14.1J/m3(Si=13.5at%)。由实验数据的分析认为Fe87-xCu1Nb3SixB9合金在高Si含量时经普通退火或纵磁退火后呈现优异的软磁特性,归因于析出的α-Fe(Si)相晶粒具有小的磁晶各向异性K1,从而导致合金具有更低的有效磁各向异性常数K所至。     

Magnetic annealing of amorphous alloys

Amorphous alloys with nominal composition of Ni40Fe40P14B6are shown to respond to annealing in a magnetic field. Coercive forces are reduced by a factor of 10 to 50 during annealing of straight ribbons to values of 0.003 Oe, as low as ever reported for potentially useful materials. Concurrently the ratio of the magnetization in 1 Oe applied field, to saturation, increases from about 0.5 to 0.95. These changes during annealing correlate with measured stress relief changes. It thus appears that most of the strain-magnetostriction contribution to the anisotropy is removed during annealing. Magnetic annealing at temperatures as low as 100°C results in noticeable changes in properties. From measurements transverse to the magneticaliy induced anisotropy axis, the induced anisotropy is calculated to be about 800 ergs/cm³, considerably smaller than obtained in crystalline Ni50Fe50. This field-induced anisotropy is reversible in direction and magnitude by reheating the sample to its Curie temperature and then cooling in a field. Annealing of 1.5 cm diameter toroids, made from 50 μm thick tapes, increases the initial permeability by more than a factor of 10 and decreases losses by more than a factor of 10. Losses and permeabilities after heat treatment compare favorably to the Permalloys with similar saturation magnetizations.     

Physical metallurgy and magnetic measurements of SmCo5-SmCu5alloys

The magnetic properties of the hexagonal intermetallic compounds involving the rare-earth and3dtransition metals have been reported in the literature. These alloys look promising as fine-particle permanent magnets. A large number of samples in the system SmCo5-xCuxwere prepared by induction melting under a protective atmosphere, and annealed at various temperatures. An outstanding feature of these alloys is their high intrinsic coercive force. After annealing at low temperatures, they show coercive forces above 20 kOe and an energy product of about 8 × 10⁶G.Oe. The most important factors determining the coercive force appear to be the chemical composition, the cooling rate, the alignment of the SmCO5-rich phase, and the annealing treatment. Examination by electron microscopy and electron probe techniques suggests a spinodal decomposition of a supersaturated solid solution into two phases, one rich in SmCo5and the other rich in SmCu5.     

Corrosion-resisting Co-Pt thin film medium for high density recording

This paper describes a new material medium for high density longitudinal recording. Sputtered Co-Pt thin films will be shown to have excellent corrosion resistance and magnetic properties. Co-Pt thin films do not need a thick overcoat like plated Co-Ni-P films do, and have higher remanent flux density than ferrite thin films. Co1-xPtx(X=0-0.60) thin films prepared by r.f. diode sputtering have a maximum Hc value near X=20. The Hc, Bs and squareness, for 20 at.% Pt film are 1,100 Oe, 12,000 G and 0.80-0.90, respectively, at 0.1 μm film thickness. These values are not changed over 1-15 Watt/cm²power densities, corresponding to 6-85nm/min deposition rates. Films with more than 28 at.% Pt have no Bs change after immersion in water for over one month, indicating that the films are passive by this test, at least. Ni additions improve magnetic and corrosion properties. There is no Bs change for Co0.070Ni0.010Pt0.020films after immersion in water for over one month. Finally, 51 KFRPI linear recording density was obtained, at D50, using a Co0.70Ni0.10Pt0.20thin film disc with a 0.46 μm gap length head and a 0.12 μm head-medium spacing.     

Development of P/M Fe–P soft magnetic materials

Phosphorous is treated as an impurity in conventional steels owing to segregation of phosphorous and formation of brittle phosphides along the grain boundaries. It is responsible for cold and hot shortness in wrought steels. In conventional powder metallurgy, involving compaction and sintering, high phosphorous content (up to 0·7%) in Fe-based alloys exhibit attractive set of mechanical and magnetic properties. These powder-processed alloys suffer from increasing volumetric shrinkage during sintering as phosphorous is increased beyond 0·6%. Thus both cast as well as conventional powder metallurgy routes have their own limitations in dealing with iron?Cphosphorous alloys. Hot-powder forging was used in the present investigation for the development of high-density soft magnetic materials containing 0·3?C0·8% phosphorous to overcome these difficulties. It was observed that phosphorous addition improves the final density of the resulting product. It was further observed that hot-forged iron?Cphosphorous alloys have excellent hot/cold workability and could be easily shaped to thin strips (0·5?C1·0?mm thick) and wires (0·5?C1·0?mm diameter). The powder hot-forged alloys were characterized in terms of microstructure, porosity content/densification, hardness, soft magnetic properties and electrical resistivity. Magnetic properties such as coercivity 0·35?C1·24?Oe, saturation magnetization 14145?C17490 G and retentivity 6402?C10836 G were observed. The obtained results were discussed based on the microstructures evolved.