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TT: Tiefe Temperaturen

TT 26: Elektronen und Phononen in HTSL

TT 26.7: Vortrag

Freitag, 30. März 2001, 12:00–12:15, A

Copper and Oxygen Nuclear Magnetic Resonance Studies of RuSr₂EuCu₂O₈ — •S. Krämer¹, G. V. M. Williams^1,2, and E. Pavarini^3,4 — ¹Universität Stuttgart, 2. Physikalisches Institut, D-70550 Stuttgart — ²The New Zealand Institute for Industrial Research, P.O. Box 31310, Lower Hutt, New Zealand — ³INFM Dipartimento di Fisica "A.Volta", Via Bassi 6, I-27100 Pavia, Italy — ⁴MPI für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart

We report the results from a zero field nuclear magnetic resonance (ZFNMR), a Cu nuclear magnetic resonance (NMR) and a ¹⁷O NMR study of RuSr₂EuCu₂O₈. This compound has recently been found to exhibit the coexistence of magnetic order and superconductivity. We find that the Cu ZFNMR frequency for temperatures above the magnetic ordering temperature is consistent with this material being an underdoped HTSC. A broad ZFNMR signal extending over 50 MHz is observed for temperatures much less than the magnetic ordering temperature which could be due to Cu or Ru. At 9 T, the magnetic order in the RuO₂ layers is predominately ferromagnetic and we find a Cu NMR signal for temperatures above and below the magnetic ordering temperature. We measured the ¹⁷O NMR spectra from 10 K to 330 K and find that the occurrence of an increasing ¹⁷O NMR shift with increasing temperature for temperature above ∼200 K provides direct evidence that RuSr₂EuCu₂O₈ is similar to an underdoped HTSC. The isotropic hyperfine coupling from Ru to oxygen in the CuO₂ layers is found to be small.