Structural Phase Transition in SrTiO3

A reminiscence of Gen Shirane at the time of his 65th birthday

by Roger Cowley

My first interaction with Gen was twenty-one years ago, when I discovered that Gen was a tough competitor whose abilities and talents are to be respected and acknowledged. It was not too many years later that I realized that it was much easier to collaborate with Gen than to compete with him, and then I further discovered how enjoyable was his and Sakae's hospitality and friendship.

We first interacted over the structural phase transition in strontium titanate. At that time I was a part of the neutron scattering group at Chalk River where I had done a large part of my thesis on neutron scattering from SrTiO3. In common with many, I felt not a little possessive about my thesis project. Gen was at Brookhaven and the HFBR had been in operation for only a few years, and the group was only just beginning to make an impact on the neutron scattering world. Gen, had of course, for many years been interested in ferroelectrics, and so SrTiO3 was a natural material on which he would wish to work. Early in 1968, Fleury, Scott and Worlock [1] performed their Raman scattering work on SrTiO3, as a result of which they proposed a definite model of the structural phase transition which could easily be tested by neutron scattering techniques. As soon as I read their paper in the July PRL, Bill Buyers, Gerald Dolling and I began work to test their theory, and showed it to be correct in a paper published [2] in January '69. Unknown to us when we began work, was that Gen and Yasusada Yamada were also working on the same project and indeed had begun before us because they had received a preprint of the Raman scattering paper. Their results were also published [3] in January '69, but at the time both Gen and I were rather annoyed with one another for straying into each other's territory.

Rereading the papers there are three points which now occur to me. Firstly, how similar the experiments were, and how similarly presented. The experiments were performed before graphite, when the choice of incident energy was less obvious than nowadays, but yet we both chose similar values, 10 and 9.3 meV. Our 3 figures are almost identical to their figures 3, 6, 7, 8 and 9. Clearly, Gen was a "talented" experimentalist!

Secondly, Gen and Sada did a more thorough experiment - as always, they had more persistence and neutron beam time. Clearly, competing with Gen was difficult. Thirdly and rather sadly, we both missed the most interesting feature of our data. We both found what we were looking for, because Fleury et al. had told us about it, but we both missed the central peak which was present in both sets of data, but which we both ignored until Tormod Riste and collaborators told us it was there. In self-defense, the problems of lambda/2 contamination were much more severe before graphite. This, however, illustrates how neutron scattering has continued to throw up unexpected results and challenges which will continue to fascinate Gen and will be solved with his unique combination of ability, enthusiasm and hard work.

Phys. Rev. Letters 21, 16 (1968).
Solid State Commun. 7, 81 (1969).
Phys. Rev. 177, 858 (1969).
Solid State Commun. 9, 1455 (1971).

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