Klaus-Dieter Liß (1), Agnes Royer (1), Tapan Chatterji (2)
(1) European
Synchrotron Radiation Facility, B.P. 220 F-38043
Grenoble Cedex
(2) Institut Max von Laue
- Paul Langevin, B.P. 156, F-38042 Grenoble
Cedex
e-mail: liss@esrf.fr
The high resolution triple axis diffractometer at the high
energy beamline ID15A
at ESRF is presented. X-ray
energies around 100 keV allow to investigate bulk material
of heavier element composition. The high resolution of 5·10-7
transverse and 5·10-6 longitudinal is demonstrated on
a perfect silicon sample with a regular pattern of deep pores
etched into one of its surfaces. Using the right scattering
strategy this reveals a large number of satellites in a
reciprocal space map [1]. Non-perfect samples up to a certain
mosaic spread can be accessed straight forward by the high
longitudinal resolution and has been applied to investigate
thermal expansion of a series of materials. Spin ordering couples
through magnetoelastic effects to the lattice parameter revealing
expansion anomalies in the anti-ferromagnet EuAs3 or
even a change of space group at the anti-ferromagnetic phase
transition in MnS2 [2]. The anormal thermal expansion
of the newly discovered inorganic Spin-Peierls system a'-NaV2O5 has been
compared to the temperature dependence of the intensity of the
3/2 1/2 15/4 superstructure reflection below the phase transition
temperature TSP and a simple extrapolation gives the
critical exponent of the second order transition [3].
References:
[1] K.-D. Liss, A. Royer, T. Tschentscher, P. Suortti, A. P. Williams, "On high resolution reciprocal space mapping with a triple crystal diffractometer for high energy X-rays" Journal of Synchrotron Radiation, (1998). 5: p. 82-89.
[2] T. Chattopadhyay, K.-D. Liss, T. Tschentscher,
"Anomalous thermal expansion due to magnetism in EuAs3
and MnS2", in "ESRF highlights".
(1997), p. 19. or
http://www.esrf.fr/exp_facilities/id15a/science/expansion_1997/expansion.html
[3] T. Chatterji, K.-D. Liß, G. J. McIntyre, M.
Weiden, R. Hauptmann, C. Geibel, "Has NaV2O5
a spin-Peierls ground state?" Physical Review Letters,
(1998). submitted.
The figure presents the temperature variation in a'-NaV2O5 in lattice spacing Dd/d along [005]. The inset on the right bottom shows the log-log plot of normalized strain e/e0 against reduced temperature t in the critical regime. The inset on the left top shows a plot of strain Dd/d along [005] at different temperatures below TSP against the integrated intensity of the 3/2,1/2,15/4 superlattice reflection which is the square of the order parameter . |