John R. Patterson

Ferromagnetic resonance and spin wave excitations in metallic glasses: The effects of thermal ageing and long-range magnetic ordering

Abstract New ferromagnetic resonance experiments under degenerate resonance conditions are reported for FeNiPB metallic glass ribbons in annealed and polished samples. An interpretation of these experimental results in terms of established theories in Ferromagnetic and Spin Wave Resonance Spectroscopy (FSWR) is proposed. The spin-wave analysis is used to interpret the effects of magnetic anisotropy on the lineshapes of metallic glasses before and after annealing. The conclusion is reached that a model of dipolar-coupled regions which assume a common resonance frequency band is appropriate in ferromagnetic metallic glasses. The role of surface pits scattering, microheterogeneities in chemical composition, clustering processes and long-range magnetic ordering in these systems is discussed in relation to the changes of glass properties by annealing. We also conclude that FSWR techniques are more sensitive than differential scanning calorimetry, X-ray scattering and static, magnetic techniques which are currently used to study structural relaxation in glasses.

The City of Rome: From Republic to Empire

This survey article — the first in a new series to be published in the Journal of Roman Studies — is an attempt to review developments in the study of the city of Rome since 1980: a decade which can reasonably be seen as one of the most exciting in this field for a century, in terms not only of the archaeological discoveries and other related research taking place in Rome itself, but also of the increasing integration of the topographical and monumental history of the city of Rome into what might be termed ‘mainstream’ Roman history.

The Archaeology of Central and Southern Roman Italy: Recent Trends and Approaches

For the historian of the Roman period, the archaeology of Central and Southern Italy raises (and sometimes provides answers to) a fascinating variety of questions. The Pontine plain and the valleys of the Liri and Sacco were the areas first affected by Roman expansion beyond the Latial plain, and it was here that the Romans tested and perfected the techniques of organization and control of territory that were to be used with such success elsewhere in Italy and eventually throughout the Mediterranean: in particular, colonization, municipalization, and the transformation of the rural landscape which accompanied them. This area too saw the development of the villa system of agriculture, which came to be predominant in Central Italy during the first century B.C., and was imitated throughout the Empire; but there were also striking differences between agricultural practices in the plains and in the mountains above. This geographical diversity was paralleled by a complex cultural mix, as aspects of both Greek and Roman culture were adopted by the local populations, who themselves moved around an increasingly unified Italy with greater ease, leading to further cultural transformations.

Ferromagnetic resonance observations of surface effects, magnetic ordering and inhomogeneous anisotropy in a metallic glass

Abstract Ferromagnetic resonance (FMR) and scanning electron microscope observations of surface effects in Metglas 2826 ribbons are presented. These effects are considered to be due to spin-wave scattering by surface pits. The considerable reduction in surface effects by a selected surface treatment allowed, for the first time, the FMR investigation of annealing effects and magnetic anisotropy. These observations are interpreted in terms of magnetic dipolar ordering and are related to recent experiments on structural relaxation in metallic glasses.