The surface magnetism of as-cast and field annealed amorphous in ribbon form has been studied by spin-polarized secondary electron spectroscopy, by recording energy-resolved spin asymmetry hysteresis loops and by scanning electron microscopy with polarization analysis. Large lateral variations in surface magnetization have been detected, indicating that , in particular, and ferromagnetic melt-spun ribbons, in general, are not suitable as standard sources of polarized electrons. Deposition of an iron film onto the did not result in a more uniform surface but rather served to emphasize the substrate magnetic structure. Thus utilization of ferromagnetic melt-spun amorphous alloys as substrates for the growth of thin magnetic films should be undertaken with caution.

Iron-boron and cobalt-boron amorphous alloys are archetypal transition metal metalloid alloys and their magnetic, electronic and mechanical properties have been extensively studied over the last 20 years. In recent years there has been much progress in understanding the electronic structure and magnetic properties of these amorphous systems within an itinerant electron approach [1-3].

This paper presents an account of the application of medium-energy ion scattering (MEIS) to the investigation of thin-film metallic multilayers grown using molecular-beam epitaxy. MEIS can provide high resolution compositional and structural information as a function of depth in the near surface region (0-250 Angstrom); these parameters are inextricably linked with the magnetic properties exhibited by materials of this type. Amongst the information available from MEIS is the accurate determination of the layer spacings, structural information from individual layers (even at thicknesses close to a monolayer), and high sensitivity to disorder in the layers. MEIS therefore provides additional information above that provided by in situ reflection high-energy electron diffraction monitoring during growth and ex situ x-ray diffraction measurements so that it represents an ideal complementary technique for the analysis of thin-film magnetic multilayer materials of this type. An Au/Fe multilayer sample of a type previously shown to exhibit giant magnetoresistance (GMR) was analyzed. Individual gold layers were clearly resolved and a measurement of the bilayer spacing obtained; this parameter determines the magnitude of the exchange coupling and GMR. Au/Fe/Au trilayer samples grown on both MgO(100) and sapphire(11 (2) over bar 0) substrates were also analyzed for a series of Fe layer thicknesses between 2 and 16 Angstrom. The MgO(100) grown samples showed unusually high second-layer Au signal consistent with atomic layer spacings in the Fe layers that lead to enhanced illumination of the second-layer Au. This effect could be modeled using bcc(100) layer spacings thus confirming the structure to be bcc(100) Fe between fcc(100) Au layers. In the sapphire-grown samples, twinned fcc(111) structure was observed in the individually resolved Au and Fe layers. The amplitude of the Fe blocking features was reduced with increasing Fe layer thickness indicating a reduction in crystallinity until for the highest thickness there was little indication of structure within the layer. The maximum layer thickness for fcc(lll) Fe growth was seen to lie between 8 and 16 Angstrom.

We have grown a series of Fe samples on Au(111) by molecular beam epitaxy. Fe was grown on Au at 30 °C and shows clear reflection high energy electron diffraction (RHEED) oscillations up to 8 monolayers, suggesting layer-by-layer growth on Au. A combined study of RHEED, medium energy ion scattering, and x-ray diffraction scans has strongly indicated that Fe initially grew as fcc(111) on Au(111) below the thickness of 3 monolayer and for the subsequent growth the Fe bcc(110) structure begins to form. Magneto-optical Kerr effect measurement has shown that the magnetization easy axis lies in the plane of the film for the thickness range from 3 to 20 Å and there is a perpendicular anisotropy when the thickness of Fe is about one monolayer.

The nature of the electron state band in the amorphous metal alloys CuHf and CuZr has been studied using synchrotron radiation as a source in photoemission experiments. In the photon energy range - 45 eV the valence band undergoes resonant photoemission which emphasizes Hf 5d-like states in CuHf and Zr 4d-like states in CuZr, while at higher photon energies contributions from these states are strongly de-emphasized because of Cooper minima in their cross-sections. The ratio of the intensities of the valence band as compared with other peaks in the spectrum characteristic of Cu or Hf (Zr) shows that the near-Fermi-level region is not wholly Hf (Zr) d-like in character, but that the degree of hybridization of these states is less than in alloys such as FeZr where both elements have partially filled shells.

Synchrotron radiation has been used to investigate resonant photo- emission in amorphous metal systems CuxZr100−x, CuxTi100−x and FexZr100−x. Constant initial state spectra reveal resonant enhancement of Zr 4d-like conduction band states near the Fermi level in Cu45Zr55 and 3d-like Ti states in Cu33Ti67 at np → nd phonon eexcitation energies; this is in contrast to the absence of resonance effects in a lower lying “filled” Cu 3d-like band. Observation of a Cooper minimum in the photoemission cross section in Cu45Zr55 gives further support to the importance of Zr 4d states near the Fermi edge. In contrast both conduction band features in Fe90Zr10 show Fe 3p → 3d resonant enhancement with some evidence of Zr 4p → 4d resonance. This is consistent with Cu45Zr55 and Cu33Ti67 exhibiting split band behaviour, while the d electrons in Fe90Zr10 appear to form a common band.

Films of amorphous NbSi prepared by magnetron sputtering were found to have a higher concentration of silicon at the surface than in the bulk material. In this paper we report on measurements of both ultraviolet photoemission spectroscopy and Auger electron spectroscopy carried out on samples prepared in situ at the UK Synchrotron Radiation Source, Daresbury. Spectra taken immediately after sputter deposition show that the surface is rich in silicon, while following argon ion bombardment the bulk composition is slowly revealed with a much greater concentration of niobium. This is observed by a comparison of the relative heights of peaks in the Auger spectra and by resonance effects and the sharpening of the Fermi edge in the UP spectra. Of particular interest are changes around the metal-insulator transition that occur at approximately 11 at.% niobium.

Ultraviolet photoemission experiments using radiation from a synchrotron source have been used to study details of the valence bands of amorhous NbxSi1-x on either side of the metal-insulator transition. The alloys were prepared in situ by RF magnetron sputtering with surface and bulk characterization obtained by Auger electron spectroscopy and EXAFS respectively. The variation of the intensities of several features in the UV spectra with photon energy are due to the presence of resonant photoemission and Cooper minima in photoionization, and these effects can be used to identify the atomic origins of the partial densities of states in different parts of the valence bands. In the metallic phase such measurements show 'pure' Nb 4d states close to the Fermi edge, whereas for the insulating material there is no Fermi edge and little evidence for the Nb resonance.

Synchrotron radiation has been used to investigate resonant photoemission in the amorphous metal systems CuTi, CuZr and CuHf. Constant initial state spectra reveal resonant enhancement at np --> nd photon excitation energies of conduction band states near the Fermi level; these are Ti3d-like states in CuTi, Zr4d-like states in CuZr, and Hf5d-like states in CuHf. In contrast there is an absence of such resonance effects in a lower lying "filled" Cu 3d-like band. The results are consistent with CuTi, CuZr and CuHf all exhibiting split band behaviour, with little hybridisation between Cu 3d and transition metal nd states.