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Reversible formation and disappearance of vacant spaces (vacancy-type defects) in bulk [Zr.sub.57][Cu.sub.15.4][Ni.sub.12.6][Nb.sub.5] [Al.sub.10] glass are directly evidenced by high-resolution, time-differential dilatometry studies. The vacancy kinetics are strongly temperature-dependent, with an effective migration enthalpy of [H.sup.M.sub.V] = 3.34 eV. This may explain the strong temperature dependence of glass properties such as viscosity. The results presented here are of general importance for understanding amorphous condensed matter and biomaterials and for the technical development of amorphous steels. bulk metallic glass | dilatometry | positron annihilation

We investigate the influence of an external magnetic field on optical photoinduced second-harmonic generation (PISHG) in [Fe.sub.18][Co.sub.60][Si.sub.9][B.sub.13] metallic glass. A correlation between the output PISHG signal and degree of crystallinity (varied by thermoannealing) is observed. The applied magnetic field essentially suppresses the relaxation time of the PISHG. Strong angular dependence of the output PISHG signal reflects the peculiarities of phase synchronism conditions that exist in certain types of glass as a result of light scattering on grains. Saturation of the PISHG at magnetic fields higher then 0.75 T indicates correlation between the magnetically induced ordering and noncentrosymmetry electron-charge density appearance. Comparison of PISHG with x-ray diffraction results indicates that the PISHG results have higher sensitivity to hyperfine magnetic ordering. A possible origin of the observed phenomena is explained on the basis of phenomenological and microscopic approaches.

Fe-based amorphous alloys in Fe- (Al, Ga)-(P,B,C, Si) system were found to exhibit a wide supercooled liquid region exceeding 50 K before crystallization. The high stability of the supercooled liquid enabled the production of cylindrical bulk amorphous alloys with diameters up to 2 mm by copper mold casting. The Fe-based bulk amorphous alloys exhibit ferromagnetism with the Curie temperature of about 600 K. The saturation magnetization (Bs), coercivity (Hc) and permeability ([[micro].sub.c]) at 1 kHz in as-quenched state are 1.07 T, 12.7 A/m and 3600, respectively, for [Fe.sub.73][Al.sub.5][Ga.sub.2][P.sub.11][C.sub.5][B.sub.4] and 1.14 T, 0.5 A/m and 3200, respectively for [Fe.sub.71][Al.sub.5][Ga.sub.2][P.sub.10][C.sub.6][B.sub.4][Si.sub.1]. Besides, the use of the Fe-based amorphous alloys enabled the production of thick amorphous ribbons above 100 [[micro]meter] in thickness and the thick samples also exhibit good soft magnetic properties. The success of synthesizing the bulk Fe-based amorphous alloys with good soft magnetic properties is promising for future development as a new type of soft magnetic materials.

We have studied the magnetization behaviour and the temperature dependence of AC-susceptibility at very low fields (5mOe to 50mOe) of glassy [Fe.sub.91-x][Zr.sub.7][B.sub.2][Ni.sub.x] (X = 0, 5, 10, 15) alloy system. At zero Ni concentration our data suggests the existence of a spin-glass behaviour at temperature below 30 K. The addition of Ni drastically modifies the magnetic properties: the antiferromagnetic exchange coupling is reduced, the magnetic moment of Fe increases from 1.58 to 2.29[[Mu].sub.B] and [T.sub.C] increases from 230 to 478 K. Thus, substitution of Fe by Ni favours the increase of magnetic order in this system.

Fine-scaled stripe domains were found by high-resolution Kerr microscopy on the surface of annealed FeCoBSi amorphous ribbons. They are caused by a dominating perpendicular anisotropy which is confined to the surface region and induced by surface crystallization. A qualitative model of the stripe domains, their reaction to magnetic fields and their origin are discussed.

The amorphous [Fe.sub.84][B.sub.9][Nb.sub.7] and its nanocrystallization have been studied by x-ray. Mossbauer spectroscopy and magnetic moment measurements. The average hyperfine field [H.sub.hf](T) of the amorphous state shows a temperature dependence of [[H.sub.hf](T) - [H.sub.hf](0)]/[H.sub.hf](0) = -0.52[(T/[T.sub.C]).sup.3/2] - 0.34[(T/[T.sub.C]).sup.5/2] for T/[T.sub.C] < 0.7, indicative of spin-wave excitation. The quadrupole splitting just above the Curie temperature [T.sub.C] is 0.41 mm/s, whereas the average quadrupole shift below [T.sub.C] is zero. The Curie and crystallization temperatures are determined to be [T.sub.C] = 330 K and [T.sub.x] = 750 K, respectively, for a heating rate of 5 K/min. The occupied area of the nanocrystalline phase at the optimum annealing temperature is about 73%.

The temperature dependencies of the effective saturation magnetostriction [[Lambda].sub.s](T) of nanocrystalline [Fe.sub.76.5-x][Cu.sub.1][Nb.sub.x][Si.sub.13.5][B.sub.9] (x = 2, 3 and 5) ribbons were measured for the samples which were annealed at 480, 500, 520 and 530 [degrees] C. The nanostructure of the samples were characterized using X-ray diffraction measurements. In [Fe.sub.76.5-x][Cu.sub.1][Nb.sub.x][Si.sub.13.5][B.sub.9] (x = 2, 3 and 5) no change of sign of the effective magnetostriction was found. On the contrary [Fe.sub.73.5][Cu.sub.1][Nb.sub.3][Si.sub.16.5][B.sub.6] ribbon annealed at 530 [degrees] C, shows at elevated temperatures a compensation point in [[Lambda].sub.s](T). We suggested two mechanisms to explain this behaviour: a) for low concentration of Si in bcc-FeSi crystallites, the negative magnetostriction was not still reached; b) for higher concentration, the Curie temperature enhancement of the amorphous matrix must be considered.

The soft magnetic properties and the stress of Co-based amorphous alloys can be varied in a wide range by changing the pressure of the sputtering gas. In this paper, the variations of the anisotropy energy of CoFeMoMnSiB thin films deposited on flexible substrate versus sputtering gas pressure are explained by a magneto-elastic model.

Theoretical analysis of weak localization for the three dimensional system presently does not include the case with strong scattering by local magnetic impurities. For paramagnetic [Fe.sub.0.33][Zr.sub.0.67] alloy, a composition just below the ferromagnetic phase boundary, the magnetic impurity scattering tune ([[Tau].sub.s]) is estimated to be comparable to the spin-orbit scattering time ([[Tau].sub.so]), but much less than the magnetic field dephasing time ([[Tau].sub.H]) or inelastic scattering time ([[Tau].sub.i]), so that the magnetic scattering occurs before the magnetic field dephasing does. When the local moments of magnetic impurities (in this case some of the Fe ions) do not interact with each other and their magnetization follows the Brillouin function, the magneto-resistance MR is proportional to [Mathematical Expression Omitted] for small (H/T), where [n.sub.s] is the density of local impurities of moment gS[[Mu].sub.B], and [Delta][Rho](H, T)/[[Rho].sup.2] should be a unique function of (H/T), for a given alloy so long as the impurities are in the Curie regime. Experimental values of the MR at several temperatures for the [Fe.sub.0.33][Zr.sub.0.67] alloy lie on a single curve of [Delta][Rho](H, T)/[[Rho].sup.2] vs. H/T

[Fe.sub.x][Ge.sub.100-x] films with compositions in the range 50[less than or equal to]x[less than or equal to]82 at 300K were deposited by rf diode, sequential sputtering from elemental targets. All the films were amorphous at 300K indicating that the Fe concentration in the stable amorphous films was increased by more than 10 at. % over that obtained by vapor deposition. The sequentially sputtered Fe-Ge films exhibited a heteroamorphous morphology with nanoscale features that varied with composition. The variations in the 4[Pi][M.sub.S] and [T.sub.c] for the sputtered Fe rich films, agreed well with data extrapolated from measurements on Ge rich evaporated films. The improvement in the soft magnetic properties produced in these films by rotating magnetic field annealing (RFA) was shown to be correlated with changes in film morphology.

Soft magnetic FeZrBCu-particles with a grain structure in the nanometer range and a coercivity of about 600 A/cm were fabricated by mechanical alloying and subsequent annealing. Domain observation by high resolution Kerr microscopy shows a patch domain structure and a inhomogeneous distribution of coercivity across the particle diameter, indicating the existence of strong inhomogeneous long-range stresses in addition to atomic level microstress. The strong stress together with an inhomogeneous microstructure is believed to be responsible for the poor soft magnetic properties of the material.

William Johnson, a professor of materials science at the California Institute of Technology, developed a substance called glassy metal-or amorphous metal-in his lab in Pasadena. The properties, benefits and drawbacks of glassy metals are discussed.