Early Years: Ferroelectric Phase Transitions and Perovskites
A reminiscence of Gen Shirane at the
time of his 65th birthday
by B. Chalmers Frazer
We have assembled here today to honor Dr. Gen Shirane in recognition of
his many important scientific achievements, and I am very pleased to
have been asked to lead off with a few comments on the early years of
his career.
Gen's contributions in neutron scattering have been so far reaching and
have had such an impact on condensed matter physics that some people,
especially among our younger colleagues, may not know that he was
already off to a very strong career start before he had ever made use
of a neutron. And indeed when he first picked up the technique of
neutron diffraction, it was to bring to bear a powerful new tool in an
area of science in which he had already established a strong
reputation: ferroelectric structures and phase transitions.
In taking only a brief look back at those early years, I think that we
can not only gain anew some appreciation of his accomplishments, but we
can also get a good indication of the Shirane that was to emerge later
in the mature scientist. In this latter respect, for example, let us
look for a moment just at what he had managed to put into print at the
time he became Dr. Shirane.
Gen Shirane received his doctorate in physics from the University of
Tokyo in 1954. According to my count, he had published a total of
35
papers up to and by the end of that year. All of these publications
were on the physics of ferroelectric crystals, and the high quality of
the work had already gained for him an international reputation in this
young but rapidly expanding field. This was impressive output by
any
standard, but it was especially so if one considers that his previous
training was not in physics, but in engineering, and the research was
carried out in the aftermath of World War II.
Looking further at these early papers, we find that 27 dealt with
members of the famous ABO3 perovskite system; the other 5
involved studies in the other then known systems: KDP, Rochelle Salt
and the pyrochlores. A few months ago, I happened to hear a talk
of
Gen's in which he jokingly commented on beginning his career with
perovskites and now again, almost 40 years later, he has been placing
his main research efforts on crystals with perovskite-derived
structures, viz. the new high Tc superconductors. He
might
also have added, of course, that he had done many important things in
between on perovskite-like materials. Gen has worked on a great
variety
of other materials also over the years, but one can readily understand
why perovskites have been appealing.
With the simple unit cell of the ideal perovskite structure, and
considering the rich diversity of physical properties and behavior
displayed by the many perovskite-like real materials, this is a
particularly attractive system for obtaining research results of
generic importance for achieving a basic understanding of phenomena in
condensed matter physics. Some of Gen's early work studying
field-induced double hysteresis loops in PbZrO3, as just one
example, led to an explanation in terms of the free energy differences
between ferroelectric and antiferroelectric phases. Also, his
extensive
work on mixed crystal systems and phase diagrams contributed
significantly to the understanding of the roles of ionic radii and
electronic structure in determining the stability of ferroelectric
phases. The experimental tools used in these and the many other
early
studies were those for dielectric measurements, x-ray diffraction,
preparative materials chemistry, etc. Neutrons were to come later.
I believe that Gen Shirane's first neutron experiment was probably one
done about 1955 with me (along with Ray Pepinsky) on the ferroelectric
structure of PbTiO3, a crystal in the perovskite system with
exceptionally large ionic displacements. We collaborated from
time to
time on a number of other neutron experiments over subsequent
years. In
looking back on those times when we worked together, my impressions are
probably similar to those of others here who have co-authored papers
with Gen. A leading one of these, certainly, is that of his
intense and
direct involvement in every aspect of an experiment. He was
prepared to
vouch for any part of a paper he put his name on as an author.
Gen Shirane has met very high standards over his many years in
scientific research, beginning at the earliest stage of his
career. In
addition to expressing our recognition of his accomplishments, we also
offer our congratulations and best wishes on the occasion of his 65th
birthday.
Last Modified: Wednesday, 26-Jan-2005 16:42:37 EST
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