Study of ferroelectrics by inelastic neutron scattering

 

M. Kempa1,2, J. Hlinka1, J. Kulda2, S. Kamba1, J. Petzelt1

 

1 Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 18221 Prague 8, Czech Republic

2 Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France

kempa@fzu.cz

 

Ferrolectrics, and particularly relaxor ferroelectrics, have been intensively studied for their unusual dielectric, electrostrictive and piezoelectric properties.1,2 The majority of ferroelectrics has a cubic perovskite structure in the parent high-temperature phase. Howevever, they exhibit a large variety of phenomena.

The optical methods (infrared, Raman spectroscopy...) are able to provide information about the dynamics only from the Brillouin zone centre. Therefore, in order to investigate lattice dynamics of single crystals, one has to employ inelastic neutron or Xray scattering.

In this contribution, we shall describe typical phenomena that can be studied on (nonmagnetic) monocrystalline materials by inelastic neutron scattering. Advantages and difficulties will be demonstrated on:

o        determination of dispersion curves3,4, in connection with constant-Energy vs. constant‑Q scans, and the new FlatCone possibility5

o        dynamics of phase transitions – diffuse scattering6, temperature behaviour of soft modes7

These properties will be followed by examples from our recent measurements.

 

1.        S. E. Park & T. Shrout, J. Appl. Phys. 82 (1997), 1804

2.        G. A. Samara, J. Phys.: Condens. Matter 15 (2003), R367

3.        J. Hlinka, S. Kamba, J. Petzelt, J. Kulda, C. A. Randall &S. J. Zhang, Phys. Rev. Lett. 91 (2003), 107602

4.        J. Hlinka, M. Kempa, J. Kulda, P. Bourges, A. Kania & J. Petzelt, Phys. Rev. B 73 (2006), 140101

5.        J. Kulda, H. Schober & S. Hayden, In: The ILL Millennium Programme, 2001, p.65. Report ILL 01CA01T

6.        J. Hlinka, S. Kamba, J. Petzelt, J. Kulda, C.A. Randall & S.J. Zhang, J. Phys.: Condens. Matter. 15 (2003), 4249

7.        M. Kempa, J. Hlinka, J. Kulda, P. Bourges, A. Kania & J. Petzelt, Phase transitions, to be published