Dresden 2003 – scientific programme
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TT: Tiefe Temperaturen
TT 19: Supraleitung: Elektronenstruktur, Phononen, Tunneln, Ordnungsparameter II
TT 19.9: Talk
Thursday, March 27, 2003, 16:30–16:45, HSZ301
Magnetism, phonons and superconductivity in RNi2B2C single crystals — •A. Kreyssig1, O. Stockert2, D. Reznik3, M. Woodward4, J. Lynn4, H. Bitterlich5, D. Souptel5, G. Behr5, and M. Loewenhaupt1 — 1TU Dresden, Inst. f. Angew. Physik (IAPD), D-01062 Dresden — 2MPI Chem. Physik fester Stoffe, D-01187 Dresden — 3CEA Saclay, F-91191 Gif sur Yvette, France — 4NIST Gaithersburg, MD 20899, USA — 5IFW Dresden, PF 270116, D-01171 Dresden
The tetragonal rare earth nickel borocarbides RNi2B2C show interesting physical properties, especially the coexistence of superconductivity and long range magnetic order. For YNi2B2C and LuNi2B2C, a strong softening behavior of low-energy phonons was reported below the superconducting transition temperatures [Kawano et al. Physica B 241-243 874; Stassis et al. Physica C 317-318 127]. Inelastic neutron scattering experiments were performed on the triple-axis spectrometers 1T1, LLB Saclay, and BT2, NIST Gaithersburg, using large TbNi2B2C and HoNi2B2C single crystals. At room temperature the observed phonon branches are similar to those of non-magnetic YNi2B2C and LuNi2B2C. Additionally, crystal field excitations occur in the same energy range. For the non-superconducting TbNi2B2C no qualitative changes in the phonon branches were observed in the temperature range down to 2 K. In the case of the superconducting HoNi2B2C the low-energy phonons show a strong softening. However, in contrast to the reported behavior for YNi2B2C and LuNi2B2C, the softening is gradual in the full investigated temperature range from 2 K to 300 K. These results suggest a new view on the mechanism of superconductivity in the RNi2B2C.