Journal of Magnetism and Magnetic Materials 269 (2004) 372–379 Pressure dependence of the magnetic structures and excitations in the giant magnetostriction compound TbCu 2 M. Rotter a , M. Doerr a, *, M. Loewenhaupt a , W. Kockelmann b,c , R.I. Bewley b , R.S. Eccleston b , A. Schneidewind a , G. Behr d a Institut f . ur Festk . orperphysik, Technische Universit . at Dresden,Mommsenstr. 13, Dresden D-01062, Germany b Rutherford Appleton Laboratory, ISIS Facility, Chilton, Didcot, Oxon OX11 0QX, UK c Mineralogisch-Petrologisches Institut, Universit . at Bonn, Bonn D-53115, Germany d Institut f . ur Festk . orper- und Werkstoffforschung Dresden, Dresden D-01171, Germany Received 13 June 2003; received in revised form 18 July 2003 Abstract A small shift of magnetic excitation energies is expected when applying pressure on a compound with large magnetostriction. We were able to observe these tiny shifts by inelastic neutron scattering on the giant magnetostriction (GMS) compound TbCu 2 . The experiments were performed at 4 and 60K using a McWhan pressure cell. The peaks in the spectra were shifted by 0.4meV to higher energies at the maximum pressure of 2GPa by the magnetoelastic interaction. This strong interaction of the crystal electric field (CF) with the lattice may be liable for the GMS effect. Moreover, neutron diffraction experiments show a weak but noticeable influence of strong external pressure on the magnetic structure of TbCu 2 . The ambient pressure magnetic propagation vector t ¼ð 2 3 10Þ at low temperatures is also preserved under pressure. The data indicate a non-collinear magnetic structure. In addition to the CF the exchange interaction also changes under pressure and leads to a slightly modified magnetic propagation vector in the vicinity of T N : r 2003 Elsevier B.V. All rights reserved. PACS: 25.40.Fq; 75.10.Dg; 75.30.m; 75.80.+q Keywords: Magnetic excitations; Neutron scattering; Pressure; Rare earth intermetallics 1. Introduction In some orthorhombic RCu 2 compounds (R=Nd, Tb, Dy) a giant magnetostriction (GMS) of several percent has been observed when applying an external magnetic field along the hard magnetic axis of a single crystal [1]. For DyCu 2 it has been shown that the GMS is connected to a phase transition from the orthorhombic CeCu 2 type to a hexagonal AlB 2 type of structure [2]. Despite efforts to explain the GMS by a strong magnetoelastic coupling [3] this increase of the lattice symmetry by an external magnetic field is not understood. Up to now no determination of the crystal field spectra by inelastic neutron scattering has been ARTICLE IN PRESS *Corresponding author. Tel.: +44-351-463-35036; fax: +44- 351-463-37734. E-mail address: doerr@physik.tu-dresden.de (M. Doerr). 0304-8853/$-see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0304-8853(03)00633-4