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TT: Fachverband Tiefe Temperaturen

TT 15: SC: Fabrication and Characterization

TT 15.1: Talk

Monday, March 14, 2011, 16:30–16:45, HSZ 301

Enhanced two-dimensional behavior of metastable T^′-La₂CuO₄, the parent compound of electron-doped cuprate superconductors — •Alexander Buckow¹, Roland Hord², Hubertus Luetkens³, Gwendolyne Pascua³, Kathrin Hofmann², Jose Kurian¹, Vladimir Pomjakushin⁴, Andreas Suter³, Barbara Albert², and Lambert Alff¹ — ¹Institute of Materials Science, TU Darmstadt — ²Eduard-Zintl-Institute, TU Darmstadt — ³Laboratory for Muon Spin Spectroscopy, PSI — ⁴Laboratory for Neutron Scattering, PSI

We synthesized crystalline bulk samples of lanthanum cuprate in the metastable T^′ phase using cesium hydroxide flux. Its crystal structure was determined as space group I4/mmm, no. 139, a = 401.02 pm, c = 1252.66 pm. Muon spin rotation reveals a gradual slowing down of magnetic order below T_N2 = 115 K, in sharp contrast to La₂CuO₄ in the T structure where T_N1 ≈ T_N2 ≈ 300 K. Our result shows that the strikingly different magnetic behavior of the two parent compounds has its origin in the two crystal structure modifications. In addition, we find that T^′-La₂CuO₄ has strongly reduced magnetic interactions compared to the other T^′ materials Nd₂CuO₄ and Pr₂CuO₄, where Nd³⁺ and Pr³⁺ are magnetic ions in contrast to the nonmagnetic La³⁺.
R. Hord, H. Luetkens, G. Pascua, A. Buckow, K. Hofmann, Y. Krockenberger, J. Kurian, H. Maeter, H.-H. Klauss, V. Pomjakushin, A. Suter, B. Albert, and L. Alff, Phys. Rev. B 82, 180508(R) (2010).