Download Syllabus: This course will teach the experimental technique of

Syllabus:
This course will teach the experimental technique of diffraction with particular emphasis on
neutron diffraction and how this can be used to gain insight and understanding of physical
phenomena in condensed matter.
Neutrons diffraction and diffraction methods in general – e.g. using photons (x-rays),
electrons and sometimes even heavy particles like protons and He atoms enable the
experimentalist to obtain microscopic information on the structure of condensed matter and
its dynamical properties on a microscopic length scale. Examples include the determination
of crystal structures, understanding of lattice vibrations and insight into magnetic phenomena
and superconductivity. Clearly the understanding of microscopic properties is essential if we
wish to understand macroscopic properties. Moreover, such a detailed understanding can
enable the design of new materials and the exploitation of their properties. E.g. the
development of recording media and the construct GBite hard disc drives was for a large part
dependent on diffraction techniques.
In this course we intend to provide a good knowledge of the design and interpretation of
microscopic investigations. The main focus will be on neutron experiments, in part for the
historical reason that we have used neutron techniques for a long time at the BER II reactor
at the Hahn-Meitner Institut (HMI) in Berlin. For a few years x-ray experiments at the BESSY
synchrotron beam are also available in Berlin and we will discuss briefly x-ray techniques.
It is clear that diffraction without a sample and a scientific problem to be solved it is in most
cases meaningless. There is a long tradition in physics of interpreting data from diffraction
experiments to reveal physical phenomena and gain insight into physical mechanisms. We
will discuss connection between neutron diffraction and other fields in solid state physics,
e.g. magnetism, superconductivity, crystallography, etc. and of course to other possible
experimental techniques which provide complementary information. We do not intent this
lecture to replace special ones on the above topics, however, we will make contact with
problems in the fields mentioned above and in each case discussed we will provide the
necessary background. In that sense, we will cover a wide area of topics in condensed
matter physics and will be multidisciplinary on all physics and experimental issues.
The organisation of course is split into “lectures” and “exercises” with the obvious division of
tasks. We will also introduce practical exercises to make a more solid connection with real
experiments. Thus, were appropriate, we may visit the neutron instruments at HMI for
practical work and we hope this will be an enjoyable exercise for all of us. For the students
who wish to pass an examination on “Neutronenstreuung” the participation on a one week
course on “neutron diffraction” at the HMI in February (outside lecture periods) is
compulsory.
At this point we should probably say a word about language: The reader may wonder that
this text is available only in English language, the reason is that some of the lectures will be
given in english, (although some can also be given in German language). For one of us (KS)
it probably means the same handicap as for some of the attending students, however, we felt
that English is the science language and probably a benefit to all of us.
To attend this course we do not expect too much prior knowledge. However quantum
mechanics and some thermodynamics knowledge is important, and ideally also some solid
state physics from the Exp.Physics lectures.
Here is a collection of main topics:
1.
2.
3.
4.
Neutrons – X-rays – electrons – basic properties
Diffraction theory: Fourier transforms, correlation functions, cross sections, crystals
Experimental: sources, resolution, detection, instruments
Inelastic scattering: Phonons, diffusion in solids, quantum mechanical treatment
Generalised cross sections
5. Magnetic neutron diffraction and magnetic materials
6. Phase transitions
7. Special topics:
7.1 Polarised neutrons
7.2 Beyond Born Approximation: dynamical theory and applications
7.3 Hot topics of current research (introduced whenever appropriate)