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Neutron Scattering
in Novel Materials
Editor: Albert Furrer
World Scientific
Neutron Scattering
in Novel Materials
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Proceedings of the Eighth Summer School on Neutron Scattering
Neutron Scattering
in Novel Materials
Zuoz, Switzerland 5-11 August 2000
Editor
Albert Furrer
Laboratory for Neutron Scattering
ETH Zurich & Paul Scherrer Institute, Switzerland
\kjh World Scientific
wKf Singapore • New Jersey 'London • Hong Kong
Published by
World Scientific Publishing Co. Pte. Ltd.
P O Box 128, Farrer Road, Singapore 912805
USA office: Suite IB, 1060 Main Street, River Edge, NJ 07661
UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE
British Library Catalogulng-in-PubUcation Data
A catalogue record for this book is available from the British Library.
NEUTRON SCATTERING IN NOVEL MATERIALS
Proceedings of the Eighth Summer School on Neutron Scattering
Copyright © 2000 by World Scientific Publishing Co. Pte. Ltd.
All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means,
electronic or mechanical, including photocopying, recording or any information storage and retrieval
system now known or to be invented, without written permission from the Publisher.
For photocopying of material in this volume, please pay a copying fee through the Copyright
Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to
photocopy is not required from the publisher.
ISBN 981-02-4444-4
Printed in Singapore by Fulsland Offset Printing
EDITORIAL
History has shown that major advances in technology are often made possible by
breakthroughs in materials science. Over the last two decades there have been major
discoveries in this field. Many new materials displaying spectacular electronic
properties and novel physical behaviours have been found, the most prominent
examples being the high-temperature copper-oxide superconductors, the colossal
magneto-resistance manganates, condensed carbon structures like fullerenes and
nanotubes, multiphase polymer blends, thin films and multilayers with manifold
applications in nanotechnology, etc. A knowledge of the structural details as well as
an understanding of the microscopic mechanisms associated with these novel
materials is obviously of great interest and crucial importance for further
developments. From the experimental point of view a rather complete insight into the
materials' properties is provided by neutron scattering techniques. The organizers
have therefore chosen the topic Neutron Scattering in Novel Materials for the Eighth
Summer School on Neutron Scattering in Zuoz.
The present volume contains the invited lectures presented at the School. The
relevant issues are thoroughly introduced, theoretically and methodically discussed,
and highlighted with experimental results by acknowledged experts. The 23 chapters
are grouped into eight parts:
The basic concepts and methods in neutron scattering are introduced by P. Boni,
A. Furrer and J. Schefer in part I. The various interactions of neutrons with
condensed matter are discussed - absorption, refraction and scattering - with major
emphasis on the cross sections for the latter process.
Part II is devoted to selected aspects in materials science. Neutron radiography
covers the range of direct imaging and inspecting techniques as discussed by E.H.
Lehmann. These techniques are beginning to be used in real time applications to
follow changes as they develop. Neutron tomography, introduced by B. Schillinger,
extends neutron radiography to three-dimensional imaging by reconstruction from a
multitude of two-dimensional radiographs. A knowledge of the chemical structure is
an essential prerequisite to the full understanding of the properties of materials. The
chapter by A.W. Hewat highlights neutron powder diffraction as the experimental
tool of choice in this field. Actual materials are not always perfect, e.g., they may
exhibit defects such as texture, strain, precipitates, voids, dislocations and
microcracks which can be studied by the combined application of neutron diffraction
(including diffuse scattering) and small angle neutron scattering as described by M.
Grosse and B. Schonfeld. Finally, R.A. Rupp gives a survey on optically active
materials with emphasis on neutron experiments to study optically active states,
optical structurization and its kinetics as well as on the electro-neutron-optic effect
and holographic grating interferometers for cold neutrons.
V
vi
Part III covers neutron scattering applications in the areas of soft condensed
matter and biology. The chapter by M. Monkenbusch gives an introduction to soft
matter systems which range from polymers to complex biomolecules. As the
constituents of these materials are light elements like H, C, N, and O, neutrons turn
out to be a unique probe particularly for experiments with H/D contrast. Examples
are provided by W. Pyckhout-Hintzen et al. and A. Arbe, who discuss the structure
and the dynamics of polymer networks by small angle neutron scattering and neutron
spin-echo spectroscopy, respectively. The importance of having access to different
length and time scales in these neutron scattering experiments is particularly
emphasized. The chapter by H.D. Middendorf deals with the dynamics of biological
macromolecules and their building blocks, which is exemplified for globular and
fibrous proteins and polypeptides. The novel technique of spin contrast variation in
macromolecular structure research is introduced by O. Zimmer.
Neutron studies of surfaces and interfaces are discussed in part IV. D. Clemens
gives an outline of the basic concepts in neutron reflectometric experiments which is
exemplified for the case of a lipid-protein membrane system. The chapter by W.
Wagner et al. deals with neutron investigations of magnetic nanocrystalline materials
whose magnetic and mechanical properties are strongly influenced by grain boundary
effects.
Some properties of rare-earth compounds are discussed in part V. L. Keller gives
several examples of magnetic ordering phenomena that include ferromagnetic as well
as commensurate and incommensurate antiferromagnetic structures as derived from
powder neutron diffraction experiments. The importance of crystal-field phenomena
on the magnetic properties is summarized by A. Mirmelstein, with illustrating
examples for different materials such as weak and hard magnets, intermediate
valence compounds, and high-temperature superconductors.
Part VI is devoted to neutron studies of magnetic excitations. B. Roessli and P.
Boni introduce the basic formalism for inelastic neutron scattering experiments
which give access to the complete spectrum of magnetic fluctuations through the
energy- and momentum-dependence of the spin susceptibility. From such studies,
exchange parameters and relaxation times can be determined which are important to
test current theories in magnetism. The chapter by N. Cavadini et al. focuses on a
family of S=l/2 antiferromagnets of dimer nature whose excitation spectra are
characterized by singlet-triplet excitations with a spin gap. These systems are
representative of a large class of gapped quantum spin systems, for which a general
phase diagram is discussed.
The emerging fields of superconductivity and superfluidity are presented in part
VII. P. Bourges shows that antiferromagnetic dynamical correlations persist over the
whole metallic state of high-temperature copper-oxide superconductors. Moreover,
the spin correlations are intimately linked to superconductivity as a sharp magnetic
"resonance" peak occurs when entering the superconducting state. S.L. Lee describes
VII
the combined application of neutron and muon techniques which both contribute
greatly to the understanding of the vortices in the mixed state type II
superconductors. J. Mesot discusses the possible connection between the magnetic
and electronic excitations measured in high-temperature superconductors by inelastic
neutron scattering and angle resolved pbotoemission experiments, respectively. M.A.
Adams summarizes the basic properties of superfluid 4He and recent inelastic neutron
scattering studies which demonstrate that 4He, despite an almost 100-year-old
history, is still not completely understood on the microscopic level.
The final part VIII contains the summary by W.E. Fischer who points out some
striking similarities in the experimental techniques and theoretical concepts for many
of the diverse topics discussed. Moreover, the complementary use of neutron,
synchrotron X-ray and muon techniques is emphasized.
Many participants presented the results of their own activities in neutron
scattering as posters which touched throughout interesting and important topics in
condensed matter research. All these contributions are not included in the present
volume, but were presented and discussed in dedicated sessions. Based on the
recommendations of a selection committee chaired by B. Dorner, three excellent
posters presented by young scientists received an award in the form of neutron beam
time at the spallation neutron source SINQ at PSI Villigen, namely:
M. Bdhm: "Magnetic solitons in CuB 0 ";
2 4
M. Plazanet: Tunnelling and vibrational dynamics in molecular crystals";
D. Sheptyakov: "Novel layered perovskite-related manganese oxide CajMnGaO^".
Sponsorship received by the Paul Scherrer Institute Villigen, the Swiss Federal
Institute of Technology Zurich, the Swiss National Science Foundation, the company
SwissNeutronics Klingnau, and the Swiss Society for Neutron Scattering is gratefully
acknowledged. The support by the Lyceum Alpinum has been efficient; we are
grateful to the direction and to all the staff members for their continuous hospitality. I
thank W. Fischer for acting as Chairman of the School. I owe gratitude to our
indefatigable secretary R. Bercher for talcing care of all the administrative tasks as
well as for cheerfully shepherding the participants during the School. I thank my
colleagues of the Programme Committee for their advice in defining the topics of the
School and guiding the participants through the problem classes. The major load in
the School was on the invited lecturers. I would like to thank them all for their
excellent presentations as well as for providing concise, though comprehensive
reviews in their fields of expertise. I am indebted to R. Bercher and H. Heer for their
assistance in the final editing of the camera-ready manuscripts. Finally the invaluable
efforts of the publisher towards a rapid publication of these proceedings are
gratefully acknowledged.
Villigen, August 2000 Albert Furrer
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ORGANISATION OF THE SCHOOL
School Director W.E. Fischer, PSI Villigen
Programme Director A. Furrer, ETH Zurich & PSI Villigen
Secretary R. Bercher, PSI Villigen
Programme Committee P. Allenspach, PSI Villigen
G. Bauer, PSI Villigen
A. Bill, PSI Villigen
P. Boni, PSI Villigen
H.B. Braun, PSI Villigen
D. Clemens, PSI Villigen
B. Delley, PSI Villigen
B. Dorner, ILL Grenoble
P. Fischer, ETH Zurich & PSI Villigen
W.E. Fischer, PSI Villigen
A. Furrer, ETH Zurich & PSI Villigen
S. Janssen, PSI Villigen
J. Mesot, PSI Villigen
R. Morf, PSI Villigen
J. Schefer, PSI Villigen
W. Wagner, PSI Villigen
Sponsors Paul Scherrer Institut (PSI), Villigen
Swiss Federal Institute of Technology (ETH), Zurich
Swiss National Science Foundation
SwissNeutronics, Klingnau
Swiss Society for Neutron Scattering
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