2-DIMENSIONAL MEASUREMENTS OF SOFT PHONONS AND PHASE-TRANSITIONS IN SRTIO3

The hat-cone instrument at the BER-II reactor in Berlin is well suited for systematic measurements of elastic and inelastic scattering event s in large and continuous areas of Q-space. With this instrument the s oft phonon branch, connected with the structural phase transition in S rTiO3, has been studied in the (hll) plane. In integral measurements t he phonon branch shows up as two triangular intensity distributions ar ound the superlattice points. The two-dimensional intensity distributi ons for a constant energy transfer reveal the anisotropy of the branch . The data collection time is considerably faster than with a conventi onal triple-axis instrument.