Amorphous Magnetic Alloys Research Articles

The Stress-Magnetic Properties of Amorphous Magnetic Alloy

Effects of internal shear stress applied by torque on the magnetic properties of Fe-based amorphous alloys were studied under weak magnetic fields of less than 800 A/m, where strips were helically bonded onto the shaft so as to form an angle of 45° with respect to the thrust direction. It was found that the permeability of each amorphous alloy in different gluing conditions reached for each sample a constant value above a certain torque and these torque values depend on the internal compressive strain applied by gluing A magnetization process model is considered to explain the above-mentioned behavior and states that the compressive stress affects the restraint of magnetic domain wall displacement.

Evidence for a rhodium moment in amorphous (FexRh1-x)80B20 alloys.

Magnetism in amorphous alloys of (${\mathrm{Fe}}_{\mathit{x}}$${\mathrm{Rh}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${)}_{80}$${\mathrm{B}}_{20}$ (1\ensuremath{\ge}x>=0.25) has been investigated. We find evidence for a sizable moment on rhodium. Our data suggest that the moment is induced discontinuously when Rh atoms have at least 4 Fe near neighbors. The $^{57}\mathrm{Fe}$ hyperfine field varies anomalously with the average transition-metal moment, which is at variance with the linear dependence reported in several Fe--transition metal--boron glasses. The observed ${\mathit{T}}_{\mathit{c}}$ variation with x fits a coherent-potential-approximation model.

Finite-temperature theory of local environment effects in amorphous and liquid magnetic alloys.

A finite-temperature theory of magnetism that takes into account the fluctuations of local magnetic moments due to structural disorder is presented on the basis of the functional-integral method and the method of the distribution function. The theory describes qualitatively or semiquantitatively the finite-temperature magnetism of liquid and amorphous metals and alloys as well as the substitutional alloys in a wide range of electron-electron interaction strength from metal to insulator. The results of numerical calculations are presented for amorphous iron. The local environment effects on the density of states, local magnetic moment, susceptibility, and amplitude of local moment are examined. It is found that amorphous iron forms an itinerant-electron spin glass at low temperatures because of the nonlinear magnetic coupling between Fe local moments and the local environment effect on the amplitude of the Fe local moment due to the structural disorder. The calculated spin-glass temperature (100 K) is in good agreement with the value extrapolated from experimental data on Fe-rich amorphous alloys.

Applications of amorphous magnetic materials at very-high magnetization rates (invited)

Amorphous ferromagnetic alloys are finding increased application in high-energy pulse-power systems and in high-frequency switched-mode power supplies. The peak powers in these applications differ by several orders of magnitude as do the core sizes; however, these applications do share similar very-high magnetization rates often measured in teslas per microsecond. In this paper the important characteristics of amorphous magnetic materials used at high magnetization rates are reviewed. Domain models for very-high magnetization rates are discussed. The effects on magnetic losses of differing voltage waveform excitations are calculated for applications which require nonconstant rates of dB/dt. Finally, several applications utilizing magnetic amorphous alloys at high magnetization rates, in both research devices and potential commercial applications, are described. Pulse-power devices based on amorphous alloy cores have already reached multiterawatt peak output power levels with pulses shorter than 100 ns. Petawatt peak-power devices are on the drawing boards.

Terawatts and nanoseconds—Metallic glasses in pulse power systems

Amorphous ferromagnetic alloys are finding an increased number of applications in high energy pulse power systems to drive accelerators and lasers. These materials, which have high saturation induction and high resistivity in a thin, strong, ribbon form, offer important advantages over conventional magnetic materials. This paper reviews the important characteristics of amorphous magnetic materials used at high magnetization rates in pulse power systems. The concepts of pulse power and of pulse compression by saturable magnetic inductors are outlined. Finally, both research devices and potential commercial applications utilizing magnetic amorphous alloys are discussed. Pulse power devices based on METGLAS®1 alloy ribbons have already reached peak output power levels of multi-terawatts TW and produced pulses shorter than 100 nanoseconds ns.

Soft magnetic properties of Co-Fe-P and Co-Fe-Sn-P amorphous films formed by electroplating

Co-Fe-P and Co-Fe-Sn-P amorphous soft magnetic alloys have been developed by electroplating. These alloys have zero magnetorestrictive compositions and show a high saturation magnetic induction B/sub s/ of 10-13.5 kG and high permeability of 3000-5000 at 5 MHz with 2- mu m thickness. It was found that the addition of Sn to Co-Fe-P improves the corrosion resistance without decreasing saturation magnetic induction. The magnetic domain structures of the thin-film head-shaped cores with Co-Fe-P amorphous films were also observed by the magnetooptical longitudinal Kerr-effect technique. It was observed that the corrosion resistivity of Co-Fe-Sn-P amorphous alloy is superior to that of Co-Fe-P amorphous alloy.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Influence of hydrogen on magnetic properties of soft magnetic amorphous alloys

The influence of electrolytic hydrogenation on the magnetic properties of three different kinds of amorphous alloys has been investigated. The alloys studied were Fe/sub 83.3/Si/sub 3.5/B/sub 11.2/C/sub 2/, Fe/sub 38/Ni/sub 38/Mo/sub 2/Si/sub 8/B/sub 14/, and (Co/sub 86/Fe/sub 5/Cr/sub 9/)/sub 75/Si/sub 10/B/sub 15/. The experimental results showed that after hydrogenation the samples became very brittle and the soft magnetic properties degraded dramatically, but saturation magnetization sigma /sub s/ and average hyperfine field increased markedly. As hydrogen evolved from the charged samples which were placed in air at room temperature, the magnetic properties, toughness, and average hyperfine field were gradually recovered. >

Taper Etching of an Amorphous Soft Magnetic CoNbZr Alloy Using an Interfacial Organosilane Layer

Tapered edge profiles in patterns of an amorphous soft magnetic alloy are obtained using wet chemical etching by applying a phenyltrichlorosilane layer between the and the photoresist. By increasing the adhesion between the and the photoresist, this interfacial layer of approximately monolayer thickness controls the penetration rate of the etchant at the interface. The etchant consists of an aqueous solution containing nitric acid and a minor quantity of hydrofluoric acid. The value of the taper angle can be adjusted between 20° and 40° by variation of the concentration of hydrofluoric acid in the etchant. The penetration rate of the etchant in the interfacial organosilane layer present at the interface varies linearly with the concentrations of both nitric and hydrofluoric acid, indicating that this process consists of a chemical reaction between the phenyltrichlorosilane and the etchant.

Mössbauer study of hyperfine field relaxations in soft magnetic amorphous alloys

Superimposed asymptotic exponential relaxation between 125 and 200°C of average hyperfine inductions and their orientations were detected by the57Fe Mossbauer spectroscopy in the ferromagnetic Fe40Ni40B20 and Fe70Co10B20 amorphous alloys.

A new type of high-resistive soft magnetic amorphous films utilized for a very high-frequency range

A new type of high-resistivity soft magnetic amorphous alloy film with a very fine two-phase heterostructure was found in cosputtered Fe-B-C films. These amorphous films are found to have a number of superior properties in the high-frequency range (over∼10 MHz) over not only regular amorphous films, but also sendust film cores, which have already been applied to high-density recording media having high coercivity. They were found to exhibit unique isotropic soft magnetic B-H curves with high Bs (∼15 000 G), low Hc (∼0.3 Oe), and high ρ (∼400 μΩ cm), and the reduced magnetization versus reduced temperature curve was almost the same as the j=∞ curve of the Brillouin function. A very high permeability with less core loss, especially in the high-frequency range, was also experimentally observed in those amorphous films.

Magnetic properties and anisotropy of amorphous Tb-Co alloys

Magnetization in amorphous alloys Tb/sub x/ Co/sub 100-x/ (10<x<40) obtained by ion sputtering in the fields of up to 70 kOe in the 1.5-300-K temperature region has been studied. Induced uniaxial anisotropy with the axis in the film plane was observed. It has been found that easy axis is reoriented under the applied magnetic field. Complex reorientation spin transitions in magnetic field applied along the hard magnetization axis have been found in Tb/sub 21/Co/sub 79/ alloy with compensated magnetic moments of Tb and Co magnetic sublattices. The obtained results are discussed on the theory of fluctuations of the amorphous alloy's magnetic moments.<<ETX>>

Anisotropy of thermal expansion for amorphous Fe 78B 13Si 9 alloy

Amorphous alloys are generally considered as fully isotropic, but only in their ideal state. Under real conditions, however, uniaxial anisotropy may be induced by the preparation techniques and conditions or by subsequent thermal, stress and magnetic field treatments. Magnetic properties have been found to be anisotropic; for example, magnetic anisotropy has been studied widely and is applied deliberately to obtain specific properties. The magnetoelastic coupling effects, although formally second-order effects, may contribute significantly to the elastic constants and their anisotropy in magnetic amorphous alloys. In addition, the difference of heat conducting conditions and subjected stress field in different orientations during the forming process may yield a certain anisotropic short range order which results in anisotropic properties in amorphous alloys. The physical and mechanical properties in experimental and theoretical work on amorphous strips formed by melt quenching have been assumed to be isotropic. The basis of that assumption is not clear. Results obtained from amorphous alloys have indicated that practically all of the specimen series tested indicated anisotropic tensile strengths. However, the anisotropy of thermal expansion coefficients and structure have not been understood in amorphous alloys. In the present work the thermal expansions in the longitudinal and transverse directions for amorphousmore » Fe/sub 78/B/sub 13/Si/sub 9/ alloy prepared by various forming conditions were investigated.« less

A Simple Model of Re‐Entrant Magnetism in Amorphous Alloys

AbstractA phenomenological model involving two kinds of self‐consistent interaction fields is shown to simulate the “re‐entrant” magnetic behaviour (i.e., mixed ferromagnetic and spin glass‐like ordering). Besides the Weiss field, it postulates fields of random directions and magnitude proportional to the mean absolute value of the local magnetic moment. Simple qualitative results are discussed and numerical results are compared with recent experiments on amorphous Fe8Ni72P10B10 alloys.

The application of amorphous magnetic alloys in induction heating medium-frequency transformers

The economics of the use of amorphous magnetic alloys in the design of medium-frequency power transformers for induction heating applications is considered in the paper. The comparison between conventional and amorphous core materials, developed on the basis of the total owning cost, shows that amorphous alloys can represent to-day a cost effective alternative to the conventional thin-lamination Grain Oriented Silicon Steel (G.O.S.S.).

Amorphous magnetic alloys near critical concentration: Low field reversible dc magnetization

Measurements of the reversible magnetization at low dc fields have been used to investigate the magnetic response near the multicritical point ( x c) of two sets of amorphous alloys. In both cases, the ferromagnetic (FM) to spin glass (SG) transition line is found to be non-monotonic. The collapse of the magnetization as x→ x + c and the rapid increase in the susceptibility as x→ x - c are suggestive of a percolation transition in the magnetic network at x= x c. From a study of the non-linear susceptibility in the most concentrated spin glass alloy in each system, we obtain scaling exponents in agreement with previous reports providing further support for a thermodynamic phase transition at the spin glass temperature. For the first time we find a divergence in the linear susceptibility in these samples similar to that expected for the non-linear susceptibility and attribute it to their proximity to the FM phase. Dramatic changes in the transition temperatures and a perceptible shift in x c are observed when normal boron is replaced by enriched boron (≈100% 11B) in one series of alloys.

High field magnetization and57Fe hyperfine field in amorphous RuxFe80−xB20 alloys

Magnetism in amorphous alloys of RuxFe80−xB20, 0⩽ × ⩽ 22 has been investigated using high field magnetization and Mossbauer spectroscopy. The average Fe hyperfine field in Ru18Fe62B20 shows an anomalous rise at low temperatures. In Ru rich alloys a low field component appears in the hyperfine field distribution and the alloys do not saturate magnetically in 80 kG fields. It is inferred that their magnetic structure is non collinear and that antiferromagnetic exchange in the system increases with Ru concentration.

Near linear temperature dependence of the thermpower in amophous FeMnB alloys

The near linear temperature dependence of the thermopower in magnetic amorphous FeMnB alloys over a wide temperature range is reported. It is due to the weakened magnetic extra contribution to the thermopower, when enough Fe atoms were replaced by Mn, whose contribution is opposite to that of the host. In this situation, using a two-component model, as an extreme simplication of the Feber-Ziman theory of liquid metal, it is able to explain the composition dependence of the thermopower.

The influence of ion plating of nickel on amorphous magnetic alloy as detected by ferromagnetic and antiferromagnetic resonance

The influence of ion plating of nickel on amorphous magnetic alloy as detected by ferromagnetic and antiferromagnetic resonance

MAGNETORESISTANCE AND MAGNETIC BREAKDOWN PHENOMENON IN AMORPHOUS MAGNETIC ALLOYS

Transverse magnetoresistance in amorphous magnetic alloys (Fe1-xCox)82Cu0.4Si4.4B13.2 were measured at room temperature and in the magnetic field range 0-15 kOe. For large magnetic field, three various functional dependences of magnetoresistance on magnetic field strength have been found as follows: (1) △ρ/ρ approaches saturation. (2) △ρ/ρ increases proportionally to H2. (3) For x = 0.15, sharp △ρ/ρ peak appears at certain magnetic field strenght in spectial angular orientation of both magnetic and electric current. The case (3) is a magnetic breakdown phenomenon. Magnetic breakdown occurs at the gap between the spin-up and spin-down sheets of the Fermi surface. This gap is the spin-orbit gap and its magnitude is a sensitive function of magnetization. Hence the magnitude and wide of the magnetoresistance peak and the magnetic field strength at the peak point are functions of angular orientation of both magnetic field and electric current.

Amorphous RE-TR magnetic alloys formed by ion mixing

Rare earth-transition metal (RE-TR) alloys are well known for their excellent magnetic properties, especially in the amorphous state. In recent years, some RE-TR alloys have been used as the recording matrix of the magneto-optical disk, in which only very thin film is required. Ion mixing is a suitable method for producing amorphous alloy films and this study was undertaken to investigate the possibility of ion mixing as an alternative way to produce such kind of magnetic alloy films. Various binary, ternary and even quadrunary combinations among RE (Gd, Tb, Nd) and TR (Fe, Cc) metals were studied by 300 keV Xe ion mixing of multilayered samples at LN 2 or room temperature. Generally speaking, amorphous alloys were formed after adequate dose irradiation, while metastable crystalline phases were observed at relatively low dose mixing stages. Ten amorphous RE-TR alloys were obtained and their Kerr rotating angles, i.e. the changing of the polarized angle between the incident and reflected laser beams interacting with the alloy surface, were measured by a He-Ne laser with a wavelength of 632.8 nm. It was found that the Kerr rotating angles of the ion mixed films were comparable or even superior to those of the alloys manufactured by sputtering technique, e.g. a Kerr angle of 48′35″ was observed for a Tb-Fe film so obtained. Experimental results of ion induced amorphous phase formation as well as the magnetic properties of the ion mixed films are reported and discussed.