The influence of applied tensile stress on power loss in Co-rich amorphous Co-Fe-Si-B ribbons with induced magnetic anisotropy

The influence on power loss PTof applied tensile stress σ in amorphous (Co0.89Fe0.11)72Mo3Si15B10(lambda_{s} > 0) and Co73Mo2Si15B10(lambda_{s} < 0) ribbons with different induced magnetic anisotropy Kuis reported. The losses are measured under sinusoidal flux conditions atf = 50Hz,J_{max} = 0.57T and atf = 400Hz,J_{max} = 0.10T. Measurements are carried out on samples in a stress-relieved state and with magnetic anisotropies induced by stress or field annealing. Atf = 50Hz, a minimum m Ptversus σ is observed. The σ-value (sigma_{min}) corresponding to the minimum PTincreases with increasing |Ku|. Atf = 400Hz, a minimum in PTversus σ is observed in the samples with induced magnetic anisotropy, whereassigma_{min} = 0in the stress-relieved samiales. However, no correlation between andsigma_{min}and Kuis possible from the present data.     

The effect of the Bsof recording head cores on the magnetization of high coercivity media

Two types of recording heads, the cores of which had different values of saturation flux density Bsand almost the same values of effective permeability, were prepared and the recording characteristics with Ni-Co plated discs of varying coercivity Hc(410-900 Oe) were examined. The materials of the head cores were a sputtered alloy (Fe-Si-Al) film (B_{s} = 11 000G) and a single crystalline Mn-Zn ferrite (B_{s} = 3800G). Results showed that the Bsof the head core had to be about five times the Hcof the media to produce the beneficial effects of high Hcon short wavelength recording. From this point of view, the alloy film head has the advantage in high linear density recording because of its large Bs. By using an experimental laminated alloy film head of narrow-track width (60 μm), the core of which had a large effective permeability (such as 115 at 40 MHz), sine-wave signals of short wavelength (smaller than 1.5 μm) and of high frequency (such as 37 MHz) were recorded on a high Hc(900 Oe) plated disc and reproduced with the same head successfully.     

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.     

Measurements on permanent magnets made from misch metal-cobalt alloy powders

Powders of a misch metal-cobalt alloy of type (MM)Co5were prepared and consolidated in various ways to study the effects of particle size, plastic deformation during milling, and pressure applied during compacting on the permanent magnet properties. Vibration grinding yields particles with high coercive force (MH_{c} = 4180Oe) but which align very poorly in a field. Mortar-ground powders have high magnetic anisotropy combined with much lower, but strongly particle-size dependent Hc. Ballmilling, a method suitable for production in quantity, constitutes a satisfactory compromise. Pressing ballmilled powder in a field with 3400 kg/cm²pressure and no binder gave optimum results. A magnet havingMH_{c} = 2010Oe,BH_{c} = 1620Oe,B_{r} = 4060G, and(BH)_{max} = 2.34MG.Oe was obtained. Details of the static and recoil behavior for this magnet are reported.     

Investigations of high-coercivity alnico alloys

For Alnico alloys containing 32-42 percent Co, 0-9 percent Ti, 6-8 percent Al, 14 percent Ni, 3 percent Cu, 0-0.5 percent S, 0-2 percent Nb, remainder Fe, the liquidus and solidus temperatures and the upper limit of the (α + γ) phase field were determined. The greatest influence is exerted by titanium in that all temperatures decrease as the Ti content increases. The influence of cobalt on temperature is considerably smaller, while sulfur has no influence at all. The addition of 2 percent Nb resulted only in the upper limit of the (α + γ) phase field being shifted to temperatures 20 to 30°C lower. Alnico alloys containing about 39 percent Co and 7-8 percent Ti were brought to columnar crystallization by controlled cooling, using a seed crystal. The seed contained 6 percent Ti and the lowering speed was between 0.50 and 3.75 cm/h. At a lowering speed of 0.50 cm/h and a temperature gradient of 5 to 10°C/mm, it was possible to obtain columnar crystallization without using a seed. The following magnetic values were obtained:(BH)_{max} = 11.0-11.7MG.Oe,BH_{c} = 1780-2100Oe,B_{r} = 8920-10 050gauss.     

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.     

On some peculiarities of the curves sigma versus temperature on alni and alnico alloys

The curves σ =f(T)are taken at a very high heating rate (1000°C/min) on samples of Alni, Alnico 5, and Alnico 8 alloys, heat treated so that their equilibrium state should correspond to a temperature of about 600°C and the α' phase particles should be much bigger than after a usual heat treatment. The Curie point occurs respectively at 760, 905, and 920°C. As we think we have avoided the diffusion process between α' and α phases, the Curie points should be those of the α' phase in almost optimal permanent magnet conditions. From that it is possible to argue that in the Alni alloy the α' phase is not pure Fe, but also includes Al and Ni; in Alnico 5 and Alnico 8 alloys, on the other hand, the ferromagnetic phase is not only Fe-Co, but also includes Al or Ni or both. In other curves taken at lower rates (300°C/min) on samples with normal morphology we observed a hysteresis of about 20-30°C between the Curie points during heating and cooling, which may be eventually ascribed to the gap between the solution and spinodal decomposition temperatures.     

Properties of amorphous alloy films mainly composed of Co--Nb

Amorphous alloy films, mainly composed of Co-Nb, have been studied by radio frequency (RF) sputtering. These amorphous films having small magnetostriction show excellent soft magnetic properties after the magnetic annealing we have developed. One of them with the composition of (Co83.5Fe2)92/85.5Nb8was found to have very high saturation magnetizationB_{s} = 14300(gauss). The effects of additives such as Zr to the alloys have been investigated and amorphous films having high crystallization temperature as well as high saturation magnetization were successfully obtained. These amorphous films show fairly good wear and corrosion resistance as well as excellent thermal stability of the magnetic properties.     

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.     

机械合金化制备Mg76-xTi12Ni12Mnx（x=2,4,6,8）合金及其贮氢性能研究

利用机械合金化法制备了Mg76-xTi12Ni12Mnx(x=2,4,6,8)合金,并研究了Mn添加量对合金贮氢性能的影响。结果表明,在Mg76-xTi12Ni12Mnx(x=2,4,6,8)合金中合金相主要由Mg2Ni和Ti2Ni相组成,合金最大贮氢量分别为3.47%、3.32%、3.60%和3.11%(质量分数,下同),合金氢化物的分解热依次为-79.2kJ/mol、-78.0kJ/mol、-73.7kJ/mol和-73.6kJ/mol,添加Mn可降低合金氢化物的稳定性,改善其热力学性能,非晶化不利于提高合金的贮氢性能。     

Temperature dependence of the effective permeability of heat treated Sendust alloys

The temperature dependence (-10°C-70°C) of the effective permeability (μeff) of Sendust alloys (Fe-9-10 wt% Si-5-7 wt% Al) quenched at a room temperature from the various temperatures (400°C-700°C) was investigated at every 2°C in the temperature range of -10°C to 70°C. Most of the studied alloys gave a peak of μeffin the studied temperature range. The peak temperature (Tp) giving the peak μeffvaried with different alloy composition. The alloys of Tp = 20°C are supposed to correspond to the alloys of the zero magnetocrystalline anisotropy constant (K1= 0) at 20°C. The deduced K1= 0 lines at various temperatures (-10°C-50°C) were obtained for an Fe-Si-Al ternary system. The values of peak μeffat the same Tp were different, depending on alloy composition, This difference is due to the difference in the polycrystalline magnetostriction constant (λ s) of the alloys. The peak temperatures of the studied alloys vary with the different heat treatments. This variation is due to the variation of K1, induced by the change in microstructures of the alloys. The variation of the values of peak μeffwith heat treatments was small compared to the difference of those in the alloys of different composition. It seems that the variation of the λ s with heat treatments would be small. Both the compositional dependence of μeffat 20°C and the temperature sensitivity (Δμeff/ΔT) were obtained for both the alloys cooled continuously to room temperature and those quenched at room temperature from 400°C.     

A2B7型La0.3Y0.7Ni3.4–xMnxAl0.1储氢合金微观结构和电化学性能研究

采用真空电弧熔炼和均匀化退火制备La0.3Y0.7Ni3.4-xMnxAl0.1(x=0~0.5)储氢合金,采用不同方法系统研究了Mn元素对合金微观结构、储氢和电化学性能的影响规律和作用。结果表明,退火合金微观组织与Mn含量关系密切,提高Mn含量有利于合金组织形成Ce2Ni7型相,当x≥0.3时,合金形成Ce2Ni7型结构单相组织。随Mn含量增加, Ce2Ni7型主相晶胞参数a、c及晶胞体积V均依次增大,导致合金吸氢平台压从0.079 MPa降至0.017 MPa,储氢量达到1.268wt%~1.367wt%。添加Mn元素能显著改善合金的电化学性能,x=0.1的合金电极的放电容量最高(390.4 mAh·g^-1);x=0.15和0.5的合金电极的容量保持率S100分别为86.1%和88.5%,具有较好的循环稳定性。上述合金电极的高倍率放电性能HRD900为71.53%~87.73%。分析结果表明,合金电极反应动力学过程由电极/溶液界面的电子转移与体相中的氢原子扩散共同控制。     

Difference between temperature dependences of both initial permeability and maximum permeability of sendust alloys

The temperature dependences (-10-50°) of the initial permeability (μ5), the maximum permeability (μmax), and the coercive force(Hc) of Sendust alloys (Fe-9 to 10 wt% Si-5 to 7 wt% Al) continuously cooled to room temperature, were investigated. Most of the studied alloys gave at least one peak value for both μ5and μmax, in the studied temperature range. The temperature giving the peak μ5agreed well with that of μmax(an effective permeability at an alternating field): the peak temperature of μeffseems to correspond to the temperature giving a zero magnetocrystalline anisotropy constant (K1= 0). The relationship between temperature and μ5was not always the same as that between temperature and μmax. From the compositional dependence of μmaxat various temperatures (10-30°C), the zero polycrystalline magnetostriction constant (λs = 0) line of the ternary Sendust alloys at each temperature could be evaluated. It is clarified that μ5of the alloys with K1< 0 is determined by both K1and λs, whereas μmaxis primarily determined by λs. When K1changes with temperature from a negative to a positive value, both μ5and μmaxof the alloys markedly decrease, independently of λs.     

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     

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.     

Magnetic properties of 6.5 percent silicon-iron ribbon formed by a melt spinning technique

Silicon-iron alloys containing 6.5 percent silicon can be formed into ribbons by a melt spinning technique. The ribbons obtained were 10-40 μm in thickness, 1-2 mm in width, and 5-10 m in length, and after annealing all of them were remarkably flexible so as to be bent 180°. The as-quenched ribbons are crystalline and are not amorphous. Low loss is maintained for frequencies up to 50 kHz for 15-μm thick 6.5 percent silicon-iron ribbons. The values obtained for as-quenched ribbon were relative permeabilitymu_{R} = 6000, and loss per cycleW_{f}/f= 30mJ/kg, measured at a maximum induction of 0.8 T and frequency of 50 kHz.     

On magnetic properties of Fe-Si-Mn alloy sheet

Fe-Si-Mn alloys composed of 3.5-7,5%, 0-3.5%Mn and 90-96.5%Fe were melted in argon and hot-rolled. Measurements of their magnetic properties and electrical resistivity indicate that the addition of manganese to higher silicon-iron alloys improves in permeability and coercive force of the alloys. Maximum permeability as high as 83000 is obtained when the alloy of 6.70%Si, 0.55%Mn and 92.75%Fe is quenched into oil from 400° after annealing at 1200° for 5 hr. The alloy exhibits the coercive force of 0.06 Oe for the maximum induction of 10 kG. The electrical resistivity of the alloy is 86 μΩ-cm, with the Vickers hardness of 355.     

Relationship of bias field setting procedure to field stability against external field perturbations for magnetic bubble memory bias field structures

In magnetic bubble memory packages having a bias field HBsupplied by a Ba-ferrite permanent magnet structure, the magnitude of HBmay be appreciably altered after setting by transient exposure to externally applied magnetic fields Hextas much as 10 times smaller than the field used in setting HB. We examine this effect for a particular magnet design having a permalloy yoke, a gap of 0.270 inches, and a saturation fieldH_{sat} simeq 240Oe. We find that the magnitude of the effect depends upon the ratioH_{B}/H_{sat}and upon the procedure used in setting HB. After setting toH_{B} = 200Oe from saturation with a demagnetizing fieldH_{ext} = -1400Oe, a remagnetizing fieldH_{ext} simeq 1800Oe is required to increase HBby 1%. On the other hand, after setting toH_{B} = 100Oe withH_{ext} = -2300Oe, a remagnetizing fieldH_{ext} simeq 400Oe is sufficient to increase HBby 1%. Setting by demagnetizing from saturation yields superior stability to setting by magnetizing from the demagnetized state, and stability of the set magnet may be further improved by demagnetizing with a ringing (alternating) field. This behavior is explained with a simple model and its importance for magnet design is discussed.     

A new principle for fast DC-sensitive potential-independent current comparators

A new principle of operation makes feasible small, cheap potential-independent current comparators whose performance reaches or exceeds the best properties of bulky magnetic amplifiers of the second-harmonic type. Connection of a ferrite-core coil in parallel with a suitable negative resistance generates relaxation oscillationsg(t). Inherently, at large oscillations the coil (i,phi)- characteristic is perfectly symmetric about the origin:phi(-i) = -phi(i). Provided that the negative-resistance (i,u)- characteristic has the same symmetry:i(-u) = -i(u), the oscillationsg(t)are perfectly symmetrical in the sense thatg(t+T/2) = -g(t). Heregrepresents either the coil flux φ, the currentior the voltageu. The time istandTthe oscillation period. External magnetomotive force shifts the coil (i,phi)-characteristics, invalidating (1) and therefore (3). Consequently, the deviation from 50% duty-ratio of the oscillatingq(t)is a sensitive and extremely stable measure of this MMF. Neither core temperature, pressure nor magnetic creep cause any zero drift. Orders of magnitude reached experimentally are: Short-time zero instability and noise:leq 10^{-5}ampere-turn, time resolution:leq 10^{-4}s, zero drift from -70 to +100°C:< 10^{-4}ampere-turn.