The resistivity and magnetic susceptibility of icosahedral Mg32(Al1-xZnx)49 have been measured for compositions between x=0.5 and x=0.69. Both quantities exhibit a stronger compositional dependence than do the same properties of the similar metallic glass Mg1-xZnx. The resistivity at low temperatures displays the classic behaviour as a function of temperature and magnetic field associated with the phenomenon of weak localization, and we are able to use this fact to measure the absolute resistivity in a way which is independent of sample geometry.

Rapidly solidified micron and submicron size droplets of Al-14 a/o Mn have been used to study the possibility of glass formation and nucleation behavior of icosahedral phase. Homogeneous nucleation of icosahedral phase is assumed, based on the high grain density (>1015 mm−3). Extremely low nucleation resistance of icosahedral phase can be understood when possible topological similarities between liquid and icosahedral quasicrystal structures are considered. Configurationally frozen liquid in Al-Mn and similar alloy systems is questionable, implying that Al-Mn “glass” probably has a microquasicrystalline structure.

Preferential crystal nucleation and growth may occur at surfaces because of a decrease in surface energy, a greater ease of diffusion and stress relaxation or a change in surface composition. Segregation as well as selective oxidation are assumed to possess the strongest influence on surface crystallization.

Crystal nucleation and growth at both surfaces of melt-spun ribbons has been studied systematically in a number of Ni-B and Co-B glasses by means of quantitative light and electron microscopy. Crystal diameter distributions indicate a transient type heterogeneous nucleatior mode for surface crystallization. The results will be compared wi th crystallization in the bulk.

We examine the implications of icosahedral symmetry on electronic structure and especially magnetic properties in alloys. From simple geometric and synmetry arguments to detailed electronic structure calculations it is clear that icosahedral symmetry carries important consequences for magnetism in a wide range of alloys. Enhanced local magnetic moments, reduced anisotropies and new magnetic domain structures are predicted. We also propose a course of further study focussed on producing a strongly magnetic quasicrystalline phase and we describe interesting new metastable Co-Er phases produced in the preliminary phase of this investigation.

This paper reviews the history of the development of films for use in magneto-optic recording. A discussion of why these early attempts with films of MnBi and Europium compounds were abandoned is given. The current work on amorphous transition metal-rare earth alloys is then reviewed. The origins of the necessary perpendicular magnetic anisotropy are discussed. The ideal combination of properties desired are: a high room temperature coercivity, a large temperature coefficient of coercivity, a large perpendicular anisotropy constant, large Ms, thermal and environmental stability, and, depending on whether a reflection or absorption mode of operation will be used, a large Kerr rotation with large reflectivity or a large Faraday rotation with a small specific absorption. These factors, their control, bow they influence the recording performance and the limits on performance of these amorphous films are discussed.

Rapid solidification onto a copper quench surface (melt-spinning) has been used to fabricate a high-performance permanent magnet alloy (Ovonic Hi-Rem™) based on the Nd-Fe-B class of materials. Crucial idditions of alloying elements are combined with careful control over quench parameters to yield a random assembly of microcrystallites, with macrosconically isotropic magnetic properties including values of remanent induction that can exceed 10 kG and maximum energy products greater than 20 MGOe. These values exceed those expected from conventional randomly oriented magnets. The enhanced magnetic performance is related to results of x-ray diffraction and electron microscopy.

Magnetic percolation has rarely been realized in Fe-based binary alloys either because Fe does not retain its moment in the dilute limit or because the solubility is too low. By using a vapor quenching method, which in our case is highrate sputtering, we have succeeded in making new metastable crystalline alloys of fcc FexCu1−x which do not appear in the equilibrium phase diagram. These alloys spanning the percolation threshold allow magnetic percolation phenomena on an fcc lattice to be observed by SQUID magnetometry and Mössbauer spectroscopy. Above xc, the magnetic ordering temperature varies as (x−xc)γ with xc = 0.185 and γ = 0.63. Below xc, spin glass ordering has been observed.

Amorphous thin films of TbFe. sputter-deposited on quartz substrates with compositions supporting polar Kerr magneto-optical behavior, and overcoated with a transparent protective layer, are studied to determine their dielectric tensor elements. Refleetivity measurements over a range of angles of incidence are made in an apparatus that corrects for the overcoat layer and exploits magnetization reversal to enhance the measurement of r⊥, the complex reflectivity associated with the magneto-optical signal. Conventional Fresnel reflectivities are also found. The theoretical model for reflectivities from a thick film magneto-optical medium at oblique incidenci is developed and used within a Levenberg-Marquardt nonlinear estimation algorithm to estimate sequentially the dielectric tensor elements, considering their widely varying magnitudes and sensitivities to errors in reflectivity data. The interpretation of the dielectric elements in terms of magneto-optical performance and structural perpendicular anisotropy is discussed.

Co-Cr thin film with the excellent c-axis orientation is required as the media for ultra high density perpendicular recording. There are two dominant factors that affect the c-axis orientation. One is the process condition such as argon gas pressure and targets-substrate distance L which change the kinetic energies of arriving atoms on substrate. The concept of mean collision number was introduced to get better understanding the relation between c-axis orientation and kinetic energy of particles. In this study, Facing Targets Sputtering (FTS) system was used because of its superiority as the plasma free sputtering. And the other is the interfacial effect between the substrate and the deposited film. In order to investigate the Interfacial effect, it has been performed to prepare the CoCr(500Å)/CoCr(500Å) double layer. By controlling the argon gas pressure, thin layers with different c-axis orientation can be easily obtained. When the c-axis well oriented 1st layer was used as the under layer, good c-axis orientation of 2nd layer was obtained even at the high argon gas pressure at which c-axis orientation in the single layer is poor. However, this improvement of c-axis orientation did not continue with the increase of the thickness of 2nd layer. It was clarified that there was the critical thickness in the 2nd layer affected by the c-axis orientation of under layer. As a result, it was concluded that the process condition was the superior dominant factor for c-axis orientation.

Pure iron thin films with soft magnetic properties and good chemical stabilities have been prepared by Dual Ion Beam Sputtering (DIBS). Four kinds of gas, that is, hydrogen, helium, nitrogen and argon were introduced respectively to the auxiliary ion source as the additional element in the film and also for the purpose of bombardment during deposition. The dependence of crystal structure and magnetic properties of the films on the preparation condition, especially, on the effect of various gases added in the films by ion bombardment onto the depositing film surface, has been investigated.

Saturation magnetization 4πMs of iron film including gas atoms is usually smaller than that of bulk iron which has 4πMs of 21.5kG. For example, 4πMs of the film prepared by conventional planer magnetron sputtering remains about 15kG. Such a remarkable difference in 4πMs may be primarily attributed to the considerable amount of argon atoms included in the film due to argon pressure as high as 10mTorr. It may be also caused by high energy particles bombarding onto the iron film surface during deposition. On the other hand, pure iron thin films prepared by Dual Ion Beam Sputtering can have 47Ms as high as 21.5kG, and coercive force Hc as low as about 4 Oe by controlling the ratio of sputtering iron atoms to argon gas atoms, impinging onto the substrate, and the arrival energies both of them. Magnetic properties and crystal structures of the iron thin films depend significantly on the kind of added gas. In this study, it has been found that bombardment and addition of adequate gas atoms with proper energy results in an improvement of atomic ordering and microscopic uniformity in the films.

Composite amorphous powder core made by field-annealing with new insulations could improve the high frequency AC magnetic and mechanical properties. All of the amorphous ribbons with composition Fe78B16Si5C and Fe40Ni38Mo4B17Si were annealed at temperature higher than their embrittlement temperature but lower than the crystallization temperature. After the ribbons become brittle, they were mechanically crushed and milled to produce powders with size about 50 ∼ 250μm. To make a core, the amorphous powders combined with insulation binder were put into an evacuted toroidal followed by hot mechanical compaction. The weight percentages of binder were about 3 wt%, 5 wt% and 10 wt%. Field-annealings were carried out for different conditions in an Ar (or N2) atmosphere chamber at elevated temperature with applied field about 10 Oe. The initial magnetization curve and saturation magnetization were measured by vibrating sample magnetometer (O≤H≤10 KOe). DC and AC magnetic properties such as permeability, coercive force, core loss, etc. were tested by B-H loop tracer. It shows the AC properties can be improved by increasing the particle size of the amorphous powder and by increasing the interparticle contacts at high frequency.

Amorphous films of TbxFe1-x are prepared by simultaneous RF bias sputtering onto various substrates and the hysteresis loops of the resulting samples are obtained both by magneto-optical and VSM loop tracers. The coercivities of the samples deposited in the same run but onto different substrates are observed to be somewhat different and these differences are discussed in light of the current understanding of the deposition process.

Observations under polarized light of magnetization reversal in thin amorphous films of TbFe alloys indicate that the reversal process is initiated at inherent nucleation sites where reverse-magnetized domains appear at fields below coercivity. The nuclei then grow in time until they cover the entire sample. The process of nucleation and growth seems to be dominated by the microstructure, since samples with identical bulk magnetic characteristics (such as composition, hysteresis loop and coercivity) exhibit quite different reversal behavior. This process is also dependent upon the history of magnetization of the sample.

Reversible structural relaxation has been studied in (Fe1-xNix)80B10Si10 by differential scanning calorimetry and X-ray diffraction. It is found that surface crystallization plays a major role in inhibiting reversibility. In consequence previously published data have presented a misleading picture about the composition dependence of the reversible effect in Fe-Ni-B-Si, which simply increases monotonically with Ni composition. There is no evidence that chemical short range order plays any role in reversibility.

Samples of Fe76RE16B8 have been prepared by melt spinning and plasma deposition. The samples were fully saturated by cooling fran 350°C in a 5 kOe field. The room temperature coercivities of these samples are reported and correlated to the microstructures revealed by scanning electron microscopy. Subsequent heat treatments are shown to either increase or decrease the intrinsic coercivities depending upon the solidification rate that each sample experienced.