Mössbauer study of amorphous Fe40Ni40PxB20−x

The hyperfine field distributions of amorphous Fe₄₀Ni₄₀P_xB_20?x (x=10, 12, 14, 17) samples before and after different heat treatments have been determined by means of Mössbauer spectroscopy. All of these P(H) curves are characterized by a main high field maximum and an additional low field maximum, respectively. The asymmetry of distributions of high field component in P(H) of Fe₄₀Ni₄₀P_xB_20?x increases progressively from Fe₄₀Ni₄₀P₁₀B₁₀ to Fe₄₀Ni₄₀P₁₇B₃. The distributions of low field component in P(H) are affected differently by the annealing temperature. The results indicate that the phospoorus element plays an important role in the hyperfine interactions of amorphous Fe₄₀Ni₄₀P_xB_20?x The influence of annealing atmosphere has been discussed.     

The effect of internal stresses on the magnetization curve of amorphous ferromagnetic FeNi alloys

The Rayleigh region, the coercive field and the magnetization curves of the amorphous, ferromagnetic alloys Fe_80−xNi_xB₂₀ and Fe₄₀Ni₄₀P₁₄B₆ have been investigated as a function of the temperature and composition. It is shown that the characteristic parameters of the magnetization curves can be described by the statistical potential theory as developed previously for the movement of domain walls. Our experimental results are compatible with the assumption that the obstacles opposing the domain wall displacements are elastic stress centres produced during the rapid quenching process of the amorphous alloys.     

Magnetization processes in the narrow domain structures of amorphous ferromagnetic alloys

The magnetization processes within the narrow domain laminae of amorphous ferromagnetic alloys have been investigated by means of the magneto-optical Kerr effect. Changes of the domain width of the closure domains by a magnetic field applied perpendicular to the laminae have been determined for the alloys Fe₈₀B₂₀ and Fe₄₀Ni₄₀P₁₄B₆. These results are compared with theoretical calculations, assuming that wall displacements within the closure domains and rotations of the magnetization in the bulk domains take place simultaneously and a stray field free domain structure is developed. It turned out, that the closure domain structure on the surface of the sample vanishes at the same magnetic field where magnetic saturation is approached.     

Mössbauer study of magnetic anisotropy and structural relaxation in amorphous Fe40Ni40P x B20−x alloys

The amorphous Fe₄₀Ni₄₀P _x B_20?x (x=0, 10, 12, 14, 17) alloys before and after annealing have been studied by means of Mössbauer spectroscopy, etc. Heat treatment of various samples were performed at 225, 250, 275, 300, 325 and 350°C, respectively, for 1 h in a quartz tube in an argon atmosphere. The results show that the magnetic anisotropy and structural relaxation in amorphous Fe₄₀Ni₄₀P _x B_20?x are related to the phosphorus element concentrations involved and the annealing temperatures. A possible mechanism of two-stage relaxation processes below the glass transition temperature is discussed.     

The pressure- and temperature dependence of the electrical resistivity of some amorphous Fe-B alloys

We report measurements of the electrical resistivity of the amorphous alloys Fe₄₀Ni₄₀P₁₄B₆ (Metglas 2826). Fe₃₂Ni₃₆Cr₁₄P₁₂B₆ (Metglas 2826A) Fe₈₀B₂₀ (Metglas 2605) and Fe₇₅B₂₅ as a function of pressure and temperature. The pressure is varied between 0 and 12 GPa, the temperature between 1.2 and 380 K. At low temperatures the pressure dependence yields additional information on the scattering mechanism.     

Existence of both spin-glass and mictomagnetic behaviour in the amorphous Fe10Ni70P14B6 alloy

Results of the accurate magnetization measurements performed on the amorphous Fe₁₀Ni₇₀P₁₄B₆ alloy in the temperature range 20–77 K in fields upto 1 kOe are reported. The complex magnetic behaviour exhibited by this alloy has been analyzed to show that a ferromagnetic ordering, occuring on a localized microscopic scale at a temperature T₀ very close to that given by the earlier Hall effect measurements, is accompanied by a superparamagnetic behaviour which below T₀ causes at first a spin-glass freezing of the magnetic spins when they interact with one another on a long range scale and then a mictomagnetic freezing of the giant superparamagnetic clusters at a lower temperature as a result of exchange interaction between their moments and the frozen spin-glass matrix. In addition, the present results, besides providing a clear physical insight into the widely different ordering temperatures obtained for this alloy from previous Mössbauer and resistivity measurements, on one hand and from our magnetization measurements on the other, strongly suggest a magnetic origin for the observed resistivity-minimum phenomenon. In conclusion, the present alloy represents a composition in the amorphous (Fe_xNi_1?x)₈₀P₁₄B₆ system well below the percolation limit.     

Stoner excitations in the strong itinerant amorphous ferromagnets FexNi80−xB18Si2 and Fe80B20

Accurate measurements of the static magnetization of the amorphous ferromagnets Fe_xNi_80?xB₁₈Si₂ (x = 15, 20, 40, 60%) and Fe₈₀B₂₀ are reported. The results are analyzed in terms of spin-wave and Stoner excitations, and the latter indicate strong itinerant ferromagnetism with a Stoner gap Δ varying between 20 and 60 K. The other fitting parameters give values of the spin-wave stiffness and a quantity simply related to the saturation magnetization. The well-known anomaly regarding the spin-wave stiffness observed in earlier measurements in thus explained quantitatively.     

Investigation of the magnetic characteristic of amorphous Fe40Ni40B20 and Fe6Co70Ni13Si7B4 foils by a magnetooptical method

Magnetic parameters, the local anisotropy field H_k, the effective field h related to the correlation radius, and the coercive force H_c, are determined for free and contact surfaces by investigating the magnetization curves of amorphous Fe₄₀Ni₄₀B₂₀ and Fe₆Co₇₀Ni₁₃Si₇B₄ foils by a highly-sensitive method of measuring the magnetooptical phase.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 49–52, November, 1989.     

Galvanomagnetic effects in Fe40Ni40B20

Hall effect and magnetoresistance measurements on the amorphous ferromagnet Fe₄₀Ni₄₀B₂₀ are reported. Both properties are approximately independent of temperature (1.5–300 K) and related to magnetization. The extraordinary Hall coefficient is 3.5 × 10^?8 m³/As. The temperature dependence of the resistivity (1.5–30 K) is also reported.     

非晶合金带制备态平面磁各向异性与技术磁性的关系

用磁转矩和磁化功方法测定Fe₄₀Ni₄₀P₁₂B₈和(Fe_0.1CO_0.5Ni_0.4)₇₈Si₆B₁₆非晶态合金带在制备态及退火后的磁各向异性常数。结果表明,用磁转矩方法测定的制备态非晶带中的平面磁各向异性常数,其中大部分是不因退火而改变的,这部分的磁各向异性对合金的技术磁化曲线无明显影响 关键词：     

Brillouin scattering from ferromagnetic metallic glasses

We report the first measurements of thermally excited surface acoustic phonons, and bulk and surface magnons from metallic glasses using Brillouin scattering. In particular we present data on the compositions Fe₄₀Ni₄₀P₁₄B₆ and Fe₈₀B₂₀. The velocity of the surface phonons was found to agree within 1.5% with the value calculated from elastic continuum theory using known bulk elastic constants. The observed field dependence of the bulk magnon frequency can be fit within experimental error to the classical relation for the k = 0 mode by including alldemagnetizing corrections. The values for the magnetization obtained from both the surface and bulk magnons agree with the bulk values determined previously with a magnetometer. The measured field dependences of the surface magnon frequency allow us to determine the g-factors, yielding 2.08±0.02 for FeB and 2.03±0.03 for FeNiPB.     

Transversal magnetic field effect on Fe40Ni40P14B6 amorphous alloys

A study about the influence of an electric current flowing through an amorphous ribbon Fe₄₀Ni₄₀P₁₄B₆ has been done. It has been found that the magnetization curves are strongly influenced by such a current (from 0 up to 5000 Hz). Bitter patterns under the action of the current have been observed in order to gain a better knowledge of these effects. The wall energy has been evaluated from a simple model.     

Magnetization reversal in amorphous (Fe1−xNix)80P10B10 microwires

The low-field magnetic properties of amorphous (Fe_1?x Ni_x)₈₀P₁₀B₁₀ are examined by measuring the local magnetic reversal field and the pinning field as function of position. Also measurements of magnetic anisotropy using FMR are reported. The observed magnetic behaviour is discussed generally. The magnetization reversal for the ideal parts of the wires may be described by the process of growth of nuclei present.     

Inverse magnetoresistance in (FeCoB)-(Al<Subscript>2</Subscript>O<Subscript>3</Subscript>) magnetic granular composites

The magnetoresistance, magnetization, and microstructure of granular composites with the general formula (Fe₄₀Co₄₀B₂₀)_x(Al₂O₃)_100?x were studied for contents of the amorphous metallic component both above and below the percolation threshold (x≈43). The low-temperature transverse magnetoresistance of the composites is negative at x=41 and practically zero for x=49. For metal contents below the percolation threshold (x=31), a noticeable (7–8%) positive magnetoresistance, reached in magnetic fields of about 17 kOe, was observed. Possible mechanisms of the generation of inverse (positive) magnetoresistance are discussed.     

Kinetics of induced magnetic directional order in a Fe40Ni40P14B6 amorphous alloy

The amorphous Fe₄₀Ni₄₀P₁₄B₆ alloy (Metglas 2826) has been annealed under magnetic field at several temperatures. The kinetics of induced magnetic anisotropy exhibits a broad spectrum (β = 4) of time constants; it obeys exactly an Arrhenius law with an activation energy of 1.74 ± 0.04 eV. These values are identical to those determined by resistivity measurements. This suggests the formation of short range directional order.     

Application of magnetically modulated microwave absorption to study of giant magnetoresistance effect in the Ni−Fe/Cu multilayer system

Magnetically modulated microwave absorption (MMMA), magnetic hysteresisM(H), giant magnetoresistance (GMR) and ferromagnetic resonance (FMR) have been examined in the antiferro-magnetically coupled Py/Cu (Py=Ni₈₃Fe₁₇, permalloy) multilayer system. The correlation between results obtained by the MMMA technique, the standard GMR measurements, and magnetization reversal studies is shown. Microwave studies of GMR, magnetization reversal, and FMR for different orientations of the magnetic field with respect to the sample surface are presented.     

A comparative study of surface oxidation behaviour of amorphous and crystallized Ni36Fe32Cr14P12B6 metallic glass using Auger Electron Spectroscopy

Native oxide and in situ oxidation of amorphous Ni₃₆Fe₃₂Cr₁₄P₁₂B₆ have been investigated at room temperature using Auger Electron Spectroscopy. The Ni₃₆Fe₃₂Cr₁₄P₁₂B₆ sample has been annealed as ～ 800 K in UHV and its oxidation behaviour has been studied at room temperature. A comparison of in situ oxidized amorphous and crystallized samples has been carried out.     

Continuous versus discrete hyperfine-field distributions in amorphous ferromagnetic iron alloys

The Mössbauer spectra of amorphous alloys possess broad absorption lines which are usually attributed to a continuous hyperfine-field distribution. The analysis of such spectra can be made simpler and less ambiguous by eliminating the second and fifth lines (the Δm_I = 0 transitions). By applying a large external magnetic field parallel to the propagation direction of the γ-ray, four-line Mössbauer spectra have been obtained for amorphous Fe₇₈B₁₂Si₁₀ and Fe₄₀Ni₄₀P₁₄B₆ (METGLAS® 2826). A discrete hyperfine-field distribution based on Bernal's liquid-structure model fits the data well. Other aspects of the results are discussed.     

The influence of the metalloid elements on the magnetic properties of amorphous Fe40Ni40PyB20−y

The Curie temperatures (T_C) and the hyperfine interactions of amorphous Fe₄₀Ni₄₀P_yB_20?y(0≤y>≤20) have been determined by ⁵⁷Fe Mössbauer spectroscopy. In this series of amorphous solid with a fixed transition-metal content, the metalloid atoms are shown to have a noticeable effect on T_C, isomer shift and hyperfine field distribution.     

Correlations between hyperfine parameters of Fe−Ni-B amorphous metals

The correlations between fluctuations in the⁵⁷Fe Mössbauer hyperfine parameters of the amorphous alloys (Fe_0.5Ni_0.5)_100?x B _x (x=16, 18, 20, 22 and 25 at%) and Fe_yNi_80?y B₂₀ (y=20, 25, 40 and 60 at%) have been determined. Values of the correlation between the fluctuations of the isomer shift and the fluctuations of magnetic hyperfine field, μ_N 〈ΔHΔδ〉 together with published values on similar amorphous systems are compared with correlation values for related crystalline phases. The lack of characteristic values suggests that the correlation values do not allow a link to be made between local structural units in amorphous alloy and crystalline phases.