Amorphous Magnetic Alloys Research Articles

Electronic structure and magnetism in amorphous alloys exhibiting local icosahedral order

The influence of icosahedral short range order on electronic structure has been investigated. We have calculated and compared the electronic structure for 13 atom Co clusters in I h and O h symmetry. The two clusters have state densities and magnetic moments which are essentially similar and closely resemble bulk properties.

Thermal stability of magneto-optic quadrilayers

The thermal stability of sputtered TbFeCo thin films in magneto-optic quadrilayer structures containing Si3N4, SiO, and SiO2 dielectrics has been examined. The observed changes in coercivity upon annealing are attributed to two parallel mechanisms: structural relaxation in the amorphous magnetic alloy and preferential oxidation of Tb at the TbFeCo/SiO and TbFeCo/SiO2 interfaces. Kinetic modeling has revealed that a spectrum of activation energies is required to explain the relaxation data, whereas a single activation energy of 1.65 eV describes the oxidation process.

Magnetic properties of amorphous metals

Neutron scattering has provided unique information about the nature of magnetism in amorphous alloys. This paper reviews some of the results obtained principally on two ribbon-form metallic glass systems - (Fe x Ni 1− x ) 75P 16B 5Al 3 and Fe x B 1− x . The former exhibits three states depending on composition: pure ferromagnetism, re-entrant spin glass, and ordinary spin glass. The neutron results provide evidence for the coexistence of spin glass and ferromagnetic correlations in the intermediate regime. The alloys of Fe and B show Invar phenomena which result in anomalously small values of the effective spin-wave stiffness calculated from low-temperature magnetization and Mössbauer data. The long-wavelength spin waves as measured by the neutrons do not reflect the rapid demagnetization found in the bulk results, implying the presence of excitation processes other than long-wave-length spin waves.

Changes in Curie temperature due to irradiation and thermal annealing in amorphous Fe20Ni60P14B6

The effects of proton (H+), deuteron (D+), and helium (He+) irradiations at 2.0 MeV on the Curie temperature of amorphous Fe20Ni60P14B6 are reported and compared to thermal annealing effects. Changes in Curie temperature are reported following isochronal anneals (5-h duration) at temperatures up to 325 °C and following room-temperature irradiations. The Curie temperature increase for samples irradiated with H+ is greater than that observed with D+, which is greater than that observed with He+. Reversibility of Curie temperature has been reported by other workers for thermal annealing of various amorphous magnetic alloys. In this paper, reversibility of Curie temperature is reported for samples successively irradiated with H+, He+, and then D+. A qualitative interpretation of irradiation effects is given in terms of transient heating about the track of a projectile ion.

Irradiation-induced decay of magnetic permeability of metglas 2605S-3 and mumetal

In order to compare the radiation resistance of amorphous and crystalline magnetic alloys, samples of commercial high-permeability alloys were irradiated with high-energy neutrons near the beam stop at LAMPF. Both crystalline and amorphous alloys showed a decrease of permeability with increasing fluence, while control samples held at the same temperature showed no change of permeability. Samples prepared from Mumetal and the amorphous alloy, Metglas 2605S-3 were tested. The permeability of the Metglas 2605S-3 sample showed a rate of decrease at least a factor of ten slower than for the crystalline alloys. The permeability decrease as a function of fluence for both alloys can be separated into two distinct stages. The first stage is thought to be due to short-range ordering which occurs at an enhanced rate due to the excess point defects produced by the irradiation. The second stage is believed to be caused by pinning of domain walls on defect clusters produced in the collision cascade.

Differences between Sputtering Methods in The Formation of Amorphous Magnetic Alloy Films

ABSTRACTFe-Si, Co-Ta and Co-Zr amorphous films have been deposited by using various sputtering methods (conventional rf diode sputtering, rf triode sputtering, dc Targets Facing type sputtering (dc TF sputtering) and dual ion beam sputtering (DIB sputtering)). The lower limit of the Si and Ta content to form amorphous Fe-Si and Co-Ta films changes significantly with the sputtering method. These differences between the sputtering methods are mainly caused by the differences in the plasma potential which affects the amount of ion bombardment to the film surface during sputtering,and the minimum content of Si or Ta to obtain amorphous films decreases as the plasma potential increases. These results indicate that the ion bombardment suppresses the growth of crystallites and promotes the formation of the films with amorphous structures. This is confirmed by the deposition of Co-Ta and Co-Zr amorphous films under the condition of various amount of ion bombardment by using a DIB sputtering system.

LOW TEMPERATURE THERMOELECTRIC POWER OF AMORPHOUS (Fe1-xCrx)84B16 ALLOYS

The absolute thermoelectric power S of amorphous metallic alloys (Fe1-xCrx)84B16 has been measured as a function of temperature in the range of 80 to 380 K for 0.01≤x≤0.46. It is found that the behavior of S(T) for the magnetic alloys does not always follow a nonlinear variation law with a shallow minimum. The. addition of a small amount of Cr (x≤0.05) is shown to lower the absolute value of S and wash out the minimum. With a larger Cr content, the alloys are weakly magnetic and the behavior of S(T) changes from nonlinear, typical of magnetic amorphous alloys, to nearly linear, similar to that for nonmagnetic alloys. A value of x of 0.15 and 0.25 is not found to have any effect on the value of 8 at the Curie temperature Tc, which happened to he in our working temperature region.

Measurements of ultra-high coupling in magnetoelastic transduction materials

Extremely high magnetomechanical coupling factors (k > 0.92) are exhibited by a new class of rapidly solidified amorphous magnetic alloys. These very high couplings produce an enormous increase in sensitivity over conventional sensor materials and make possible a wide variety of new applications. New techniques have been developed to determine coupling factors close to unity with a great deal of precision. Measurements were performed using standard resonance techniques for bar shaped samples, but with two significant improvements in data analysis: (1) Multiple resonances are readily observed in these materials. Inclusion of a mechanical loss Q factor in the basic resonance function for the bar allows a good fit to the data over the entire multiresonance spectrum. Such a fit yields significantly more accurate coupling factors than can be obtained by the standard methods. (2) The problem of appropriate assumptions of magnetic boundary conditions, which is unique to metallic magnetoelastic materials and is due to the presence of eddy currents, is satisfactorily resolved by making use of the higher resonance data.

On the validity of 57Fe hyperfine field distribution calculations from Mössbauer spectra of magnetic amorphous alloys

The approximations which are made in 57Fe hyperfine field distribution calculations from magnetic amorphous alloys are discussed. A diagram which gives an immediate indication of the validity of a given hyperfine field distribution obtained using first order perturbation theory is proposed. The assumption about the distribution of the polar angles of the hyperfine field direction with respect to the EFG principal axes in transition metal-metalloid amorphous alloys is discussed. The asymmetries of the Mössbauer spectra of the latter alloys are also considered.

Magnetic properties of amorphous thin films produced by ion mixing

We have produced several magnetic amorphous alloys by ion mixing of thin multilayer films. Our results show that the ion mixing technique is able to produce amorphous films of the various categories (transition metal-metalloid, transition metal pairs) at the composition appropriate for the appearance of magnetic ordering. A comparison of their saturation magnetization with that of related vapor quenched films suggests similar nearest-neighbor coordination in both kinds of samples.

Effects of neutron irradiation on magnetic permeability of amorphous and crystalline magnetic alloys

In order to compare the radiation resistance of amorphous and crystalline magnetic alloys, samples of commercial high-permeability alloys were irradiated with high-energy neutrons near the beam stop of LAMPF. Both crystalline and amorphous alloys showed a decrease of permeability with increasing fluence. Samples prepared from Permalloy (crystalline) and the amorphous alloys Metglas 2605S-3 and 2705M were tested. The permeability of the Metglas 2605S-3 sample showed the slowest rate of decrease, being at least a factor of ten slower than for the Permalloy. The permeability decrease as a function of fluence for Metglas 2605S-3 appears to occur in two stages. It is proposed that the first stage is due to directional short-range ordering that occurs at an enhanced rate due to the excess point defects produced by the irradiation. The second stage is thought to be caused by pinning of domain walls by defect clusters produced by the collision cascade.

Experimental evidence for magnetic two level systems in spin glasses (invited)

We report about low temperature measurements of susceptibility, magnetization, and time dependence of the thermoremanent magnetization on amorphous magnetic alloys (PdCuSi) with transition metals Mn, Fe, and Co in a concentration of x=5 to 20 at. %. Alloys with low concentrations show single peak spin-glass behavior. The more concentrated samples show magnetic double transitions, with an upper transition at Tc into a ferromagnetic state, followed by a lower transition at Tg into a state which has a spin- or cluster-glass character. Evidence for this comes from the onset of irreversibility and time dependence of the remanence, features which are absent above Tg. The results can be interpreted by thermal relaxation of cluster moments over anisotropy barriers, or in an equivalent picture by the existence of magnetic two-level systems (MTLS). Direct evidence for the existence of MTLS comes from investigations of the phonon thermal conductivity κPh(T) studied as a function of temperature and magnetic field. Enhancement of κPh(T) in a field of 5 T is found for Fe and Co, yet only in the cluster-glass range T<Tg. We conclude that the phonons, coupled via a 1-s coupling to the cluster moments, scatter inelastically from the MTLS; i.e., the phonons excite the magnetic clusters over their anisotropy barriers. The results are discussed within the framework of a phenomenological model describing the low temperature properties of spin glasses in terms of a distribution of asymmetrical double well potentials.

Study of electronic structure of some amorphous magnetic alloys

The electronic structure of crystalline Fe and amorphous alloys Fe 80B 20 and Fe 86B 14 is studied by using the XPS technique. The valence band spectra (VBS) of amorphous alloys are similar to that of crystalline iron; the core-level energies are the same as for pure elements and the metallic nature of Fe is retained. After annealing in the crystallization temperature range, new features in the VBS and core-level shifts were observed. This effect is, we suppose, due to the reaction with oxygen dissolved in the surface region of the Fe-B alloy. The different effects of annealing on XPS spectra observed for both compositions are connected with their different mechanisms of crystallization.

Hydrogen in amorphous magnetic rare earth-transition metal alloys

A wide range of hydrogenated amorphous rare earth-transition metal (R-T) alloys has been synthesized using a newly developed vapor deposition synthesis procedure. Measured H/R ratios vary from 2 to 5 depending on composition. The R-T films do not fracture or disintegrate when activated as do crystalline alloys. Magnetic and electrical results are given for the a-Gd xFe 1−x system. The inclusion of hydrogen sharply reduces the compensation temperature by 200K and the Curie temperature by 50K at a given composition. The dominant magnetic effect is a reduction of the GdFe exchange interaction. Potential application advantages of hydrogenated amorphous R-T alloys are also discussed.

An Introduction to Mössbauer Studies of Magnetic Materials

A straightforward introduction to Mossbauer spectroscopy is presented along with a brief background to its discovery over 25 years ago. Several applications of Mossbauer spectroscopy in the study of condensed matter are described. The examples are based on recent investigations of the mixed magnetic AuFe system and amorphous alloys and show how Mossbauer spectroscopy can be used to obtain information on local atomic order, magnetic phases and texture. The diverse range of applications of Mossbauer spectroscopy is outlined, including a brief discussion of its use in topics of current interest in metal physics.

METGLAS ALLOY 2605CO

Abstract METGLAS Alloy 2605CO is an amorphous iron-base soft magnetic alloy. It has the highest saturation induction of any amorphous alloy commercially available, combined with very low core loss. It is the alloy of choice when low weight is as important as efficiency. It is particularly suited to 400 Hz aerospace applications where small core size is a requirement, and to pulse applications where maximum flux swing is desired. This datasheet provides information on composition and physical properties. It also includes information on forming and heat treating. Filing Code: Fe-69. Producer or source: Allied Corporation, Metglass Products Department.

Resistance of the amorphous magnetic alloy Fe 29Ni 49P 14B 6Si 2 as a function of temperature and stress

The stress and temperature dependence of the electrical resistivity of amorphous alloy ribbon Fe 29Ni 49P 14B 6Si 2 in the range 77–440 K is reported. Tensile stress was applied along the long ribbon axis. Results obtained on the temperature dependence of Δ R R 300 show that at low temperatures (<320 K) the tensile stress has an effect of increasing the slope while at high temperature it seems to be reverse, indicating the initiation of enhanced structural relaxation process. Curie temperature is found to increase with application of the tensile stress. Ferromagnetic Resonance (FMR) and Scanning Electron Microscope observations show that the applied tensile stress induces crystallization into the specimen which is reflected through broad FMR peaks. Crystallites seem to be elongated parallel to the direction of the applied stress.

Structural relaxation and magnetism in amorphous alloys

Structural relaxation phenomena in amorphous alloys caused by post-quenching heat treatments are discussed in relation to the magnetic properties. It is pointed out that both microscopically irreversible and reversible relaxation processes exist, and are related to the changes in the atomic level density fluctuation and shear fluctuation, respectively. The importance of the microscopic variables in determining the kinetics of the reversible relaxation process is emphasized.

Influence of the viscosity field on the power losses in amorphous magnetic alloys

Thermal annealing of an amorphous alloy showing large viscosity field effects, as Metglas 2826, produces a strong reduction of the dynamic loss, probably related to a corresponding reduction of the viscosity field. The effect is not related to changes in the magnetic domain structure due to the anisotropy induced when the material is annealed under magnetic field, but seems to be simply related to a stabilization of the amorphous atomic structure.

METGLAS ALLOY 2605S-3

Abstract METGLAS Alloy 2605S-3 is an amorphous iron-base soft magnetic alloy that can be annealed to obtain a round B-H loop which results in very low core loss at high frequencies (&amp;gt;1kHz). Because of its high saturation induction relative to ferrites or permalloys, significant size reductions are possible in high-frequency devices by utilizing this alloy. Unlike ferrites, it is suitable for use over a wide operating temperature range without cracking or showing large drops in usable flux density. Its uses include numerous high-frequency devices. This datasheet provides information on composition and physical properties. It also includes information on forming and heat treating. Filing Code: Fe-68. Producer or source: Allied Corporation, Metglass Products Department.