时效工艺对PtCo合金磁性能的影响

研究了时效温度对PtCo合金磁性能的影响.磁性能测量结果显示,随着时效温度的增加合金的剩磁逐渐减小,时效温度为690 ℃时,合金的矫顽力达到最大值.第一步时效处理后,合金的有序度S随时效温度的提高而增加,长程有序度的增加说明合金有序相的晶粒尺寸也在增加,这是合金矫顽力变化的根本原因.第二步时效处理后,PtCo合金的微观组织结构不发生改变,有序相的各向异性场增大,使合金的矫顽力增大. 关键词： 时效温度 PtCo合金 磁性能 有序度     

Surface and bulk magnetic properties of as-quenched FeNbB ribbons

The surface and bulk magnetic properties of amorphous FeNbB ribbons in as-quenched state are investigated using various non-destructive methods. The conversion electron Mössbauer spectroscopy has detected the presence of crystalline phase at both surfaces of ribbon sample while the bulk was amorphous. The coexistence of crystalline and amorphous phase was shown also in the X-ray diffraction pattern. Magnetic properties measured by bulk sensitive vibrating sample magnetometer (VSM) strongly differs from the surface characteristics investigated by magneto-optical Kerr effect (MOKE).     

The effect of chromium on the magnetic properties of elinvar alloys

A study was made of the magnetic properties of alloys of the Fe-Ni-Cr system with varying chromium content in strong fields at room temperature. The processes which govern the magnetization of these alloys were determined. It is shown that the presence of chromium in the alloy has a marked effect on its magnetic properties. The chromium content determines the saturation magnetization, the anisotropy constant and the susceptibility of the paraprocess.     

Effect of thermal annealing on the magnetic properties of thin films of Co-Pd alloys

The results of studies of the effect of thermal annealing on the magnetic properties of thin films of Co-Pd alloys are described, along with a method for obtaining easy-axis perpendicular anisotropy in these materials. The method consists of depositing layers of the alloy on a substrate whose thermal expansion coefficient is considerably smaller than that of the film, and then annealing it in a vacuum. This method is used to prepare samples with rectangular hysteresis loops for magnetization perpendicular to the plane of the film, coercive forces of 750 Oe, and Kerr rotation angles of 0.21°. Also presented are the results of experiments on thermomagnetic recording on the samples. Zh. Tekh. Fiz. 68, 66–70 (April 1998)     

The effect of Nb addition on the thermal stability and magnetic properties of Fe-based amorphous alloys with a wide supercooled liquid region

We have examined the effect of Nb addition on the thermal stability of the supercooled liquid before crystallization, the glass-forming ability and magnetic properties for the amorphous alloy series Fe₇₃Nb_xAl_5-xGe₂P₁₀C₆B₄ and Fe₆₃Co₇Nb_xZr_10-xB₂₀. The supercooled liquid regions (ΔT_x=T_x-T_g) have maximum values of 66 and 79K, respectively, for Fe₇₃Nb₁Al₄Ge₂P₁₀C₆B₄ and Fe₆₃Co₇Nb₄Zr₆B₂₀ alloys. The saturation magnetization σ_s of the Fe₇₃Nb_xAl_5-xGe₂P₁₀C₆B₄ alloy system is much higher than that of the Fe₆₃Co₇Nb_xZr_10-xB₂₀ alloy system, and is almost unchanged with an increasing Nb content from 0 to 3 at%. But the σ_s of the Fe₆₃Co₇Nb_xZr_10-xB₂₀ alloys decreases linearly with increasing Nb content. The coercive force H_c of the two alloy series can have a minimum value of 31A/m for Fe₇₃Nb₁Al₄Ge₂P₁₀C₆B₄ and 37A/m for Fe₆₃Co₇Nb₄Zr₆B₂₀. All these values are for the ribbons annealed at 773 and 873K for 15min in vacuum.     

Thermoelectric properties of Ge-doped Bi85Sb15 alloys at low temperatures

Bulk polycrystalline Bi₈₅Sb_15−xGe_x (x=0, 0.5, 1, 1.5, 2) composites were prepared by mechanical alloying followed by pressureless sintering. The thermoelectric properties were studied in the temperature range of 77–300 K. The results indicate that increasing the Ge concentration causes the Seebeck coefficient to change sign from negative to positive. Moreover, it is found that the maximum value of the Seebeck coefficient can be precisely controlled with the Ge concentration. The maximum dimensionless figure of merit reaches 0.07 at 140 K. These results suggest that the preparation of p-type Bi–Sb alloys is possible by using the Ge-doping approach.     

Magnetoelasticity and effect of thermal phonons on the magnetic properties of ferromagnets

The experimental data for a series of ferromagnets are analyzed to determine quantitatively the magnetoelasticity-reduced effects of thermal phonons on the magnetic properties of ferromagnets. It is shown that thermal phonons have an anomalously strong effect on the magnetic properties of Invar iron-platinum alloys. The effect is governed by shear magnetoelasticity. Pis'ma Zh. éksp. Teor. Fiz. 64, No. 1, 33–37 (10 July 1996)     

Amorphous Heusler alloys: The effect of annealing on structure and magnetic and transport properties

Alloys with the Heusler compositions Cu₂MnIn, Cu₂MnAl and Cu₂MnSn have been prepared as amorphous films for the first time. The structural disorder results in as-deposited films which are not ferromagnetic and, in fact, exhibit spin-glass properties due to the distribution of MnMn distances and co-existence of positive and negative exchange interactions. Annealing of the In and Al alloys can restore single phase ordered Heusler structures which are ferromagnets with Curie temperatures typical of bulk alloys. The calculated Mn moments remain lower than the bulk values of 4 μ_B probably due to disorder at grain boundaries. Films annealed under non-optimum conditions crystallized into several non-magnetic structures as well as the magnetic L2₁ Heusler phase. Lattice constants of all phases were determined. The temperature dependence of resistivity through the amorphous-crystalline transformation was found to confirm the results of thermal annealing on structure and magnetization.     

The effect of magnetic field on the electrodeposition of CoFe alloys

The superimposition of a homogenous magnetic field during an electrodeposition of CoFe alloy was investigated. A magnetic field superimposed parallel to the electrode surface increases the limiting current density and the deposition rate due to the magnetohydrodynamic (MHD) effect. The deposits obtained in this field configuration appear smoother and more homogenous than the ones obtained without the magnetic field. On the contrary, a magnetic field superimposed perpendicular to the electrode surface does not influence significantly the electrochemical reaction but the morphology of the deposited layers is strongly affected. The roughness is strongly increased in this field configuration and grains grow as separated columns aligned perpendicular to the electrode surface, in the field direction. A magnetic field applied during the deposition affects the magnetic properties of the deposited layers as well. These changes are discussed with respect to the surface roughness and the internal stress state of the layer.     

The influence of Cr content in Fe-Cr-Co alloys on the magnetic properties and Mössbauer effect

Fe-xCr-8Co (x=24, 25, 27, 29 and 32 wt%) permanent magnetic alloys have been studied bv Mössbauer effect, magnetic balance and vibrating-sample magnetometer. It is indicated that the optimum permanent magnetic properties obtained for the composition of the alloys at about x=27. The value of Cr content in these alloys sigificantly influences the average hyperfine field, the saturation magnetic moment, the proportion of paramagnetic phase and orientation of magnetic moment in these alloys. The intrinsic coercive force is gradually reduced with the temperature decreasing from 290 to 77k. The paramagnetic peak in the spectrum disappars at about 125k. The certain mechanism has been suggested to explain the experimental results.     

The effect of hydrogen on the properties of invar alloys

The characteristic weak internal field contribution of a Mössbauer spectrum of Fe-Ni Invar alloys was diminished by an intense hydrogenation, and instead, the strong ferromagnetic part increased. This effect of hydrogen was interpreted in terms of 3d hole filling with electrons from solute hydrogen in Stoner's band model.     

Role of compositional changes on thermal,magnetic, and mechanical properties of Fe-P-C-based amorphous alloys

This work aimed to tune the comprehensive properties of Fe-P-C-based amorphous system through investigating the role of microalloying process on the crystallization behavior,glass forming ability(GFA),soft magnetic features,and mechanical properties.Considering minor addition of elements into the system,it was found that the simultaneous microalloying of Ni and Co leads to the highest GFA,which was due to the optimization of compositional heterogeneity and creation of near-eutectic composition.Moreover,the FeCoNiCuPC amorphous alloy exhibited the best anelastic/viscoplastic behavior under the nanoindentation test,which was owing to the intensified structural fluctuations in the system.However,the improved plasticity by the extra Cu addition comes at the expense of magnetic properties,so that the saturation magnetization of this alloying system is significantly decreased compared to the FeCoPC amorphous alloy with the highest soft magnetic properties.In total,the results indicated that a combination of added elemental constitutes,i.e.,Fe69Co5Ni5Cu1P13C7 composition,provides an optimized state for the comprehensive properties in the alloying system.     

The effect of pressure on the thermal conductivity of ordered and disordered alloys

A comparison is made between the results from experimental studies into the effect of hydrostatic pressures of up to 400 MPa in the temperature range 273–523 K on the phonon thermal conductivity of CdSnAs₂ alloy and the effective thermal conductivity of granite. Pressure was demonstrated to lead to a change in the degree of structural ordering of the studied specimens.     

Effect of aging on the magnetic properties of Cu-Mn alloys

The susceptibility of Cu-Mn alloy specimens quenched into cold water from 850°C increases proportionally with the cumulative period of subsequent aging at 100°C at least up to four weeks. The rate of increase varies over wide limits, even with the same specimen after requenching, apparently due to inadvertent slight variations in the quenching process. This large scatter in the rate of aging may account for at least some of the apparently contradictory results reported in the literature.     

Transport properties of dilute magnetic alloys

The electrical resistivity, thermopower, and the electronic part of the thermal resistivity of dilute magnetic alloys are calculated in the framework of the Suhl-Nagoaka theory. Using Bloomfield's and Hamann's solution of the Nagaoka equations, we derive expressions for the transport quantities in the limitT? ¯ T_K andT?¯ T_K to order (In ¯T _K /T)^?4 where ¯T _K is the Kondo temperature which may depend on the spin independent scattering. We find that the thermopower and deviations from the Wiedemann-Franz law in this limit decrease as ¦In ¯T_K/T¦^?3 if one neglects a trivial temperature dependence of the thermopower due to the electron-phonon interaction.     

Note on the magnetic properties of amorphous rare-earth nickel alloys

The magnetic properties of several amorphous rare-earth nickel alloys close to 30 at% Ni have been studied in the temperature range 4.2–300 K. The Curie temperatures range from 2 K in Pr₆₉Ni₃₁. Alloys in which the rare-earth component has an orbital moment show large intrinsic coercive forces below T_c. These coercive forces vary considerably with temperature, the temperature dependence of the alloys Dy₆₉Ni₃₁ and Tb₆₉Ni₃₁ is satisfactorily described by means of an exponential law of the form H_c(_T) = H_c(0) exp(-αT).     

The stress effect on magnetic domain structure of Fe-Co amorphous alloys

The stress effect on magnetic domain structure has been studied for the Fe-Co amorphous alloy system. The domain structure was dominated by the magnetostriction-internal stress coupling. By applying the tensile stress, the domain structure was changed significantly according to the magnitude and sign of magnetostriction. The value of internal stress estimated was about 3×10⁸ dyn/cm² and nearly constant for all the alloy composition.     

Beneficial effect of rapid recurrent thermal annealing on magnetic properties of SmCo-based films

The effects of conventional thermal annealing (CTA) and rapid recurrent thermal annealing (RRTA) on the magnetic properties of the SmCo-based films were investigated. The results show that the CTA-treated films exhibit amorphous structure with coercivity insensitively depending on annealing parameters as anticipated. As for the RRTA-treated films, single TbCu₇-type phase structure with well crystallization is observed. The coercivity of the RRTA-treated films is strongly correlated with annealing parameters, and its optimum value is larger than that of the CTA-treated films. It is suggested that the RRTA treatment has beneficial effects on the magnetic properties of the SmCo-based films.     

The effect of isotopic substitution on the thermodynamic properties of palladium-hydrogen alloys

An attempt has been made to predict the thermodynamic properties of the Pd-D and Pd-T systems from those of the Pd-H system. By considering only the isotopic dependence of the optic modes, a satisfactory interpretation of the infinitely dilute solutions is not possible. However, using only the isotopic dependence of the optic modes together with an empirical equation for the infinitely dilute solution yields calculated results for the concentrated solutions in both the single and two phase regions which are in excellent agreement with the experimental results for the deuteride and tritide systems.