Université de Fribourg

Muon-spin rotation study of magnetism in NaxCoO₂ single crystals with 0.78 ≼ x ≼ 0.97

Bernhard, Christian ; Niedermayer, Ch. ; Drew, Alan J. ; Khaliullin, G. ; Bayrakci, S. ; Strempfer, J. ; Kremer, R. K. ; Chen, D. P. ; Lin, T. ; Keimer, B.

In: Europhysics Letters, 2007, vol. 80, no. 2, p. 27005

By muon spin rotation we investigated the magnetic properties of a series of highly Na-doped NaxCoO₂ single crystals with 0.78(1) ≼ x ≼ 0.97(1). Our data provide evidence for an intrinsically inhomogeneous magnetic state which can be described in terms of hole-doping (Na vacancy)-induced magnetic clusters that percolate at 1−x≳0.04 until they yield a bulk...

Université de Fribourg

Dimensionality control of electronic phase transitions in nickel-Oxide superlattices

Boris, A. V. ; Matiks, Y. ; Benckiser, E. ; Frano, A. ; Popovich, P. ; Hinkov, V. ; Wochner, P. ; Castro-Colin, M. ; Detemple, E. ; Malik, Vivek Kumar ; Bernhard, Christian ; Prokscha, T. ; Suter, A. ; Salman, Z. ; Morenzoni, E. ; Cristiani, G. ; Habermeier, H.-U. ; Keimer, B.

In: Science, 2011, vol. 332, no. 6032, p. 937-940

The competition between collective quantum phases in materials with strongly correlated electrons depends sensitively on the dimensionality of the electron system, which is difficult to control by standard solid-state chemistry. We have fabricated superlattices of the paramagnetic metal lanthanum nickelate (LaNiO₃) and the wide-gap insulator lanthanum aluminate (LaAlO₃) with atomically...

Université de Fribourg

Pseudogap and precursor superconductivity in underdoped cuprate high temperature superconductors: A far-infrared ellipsometry study

Dubroka, Adam ; Yu, Li ; Munzar, Dominik ; Kim, KyungWan ; Rössle, Matthias ; Malik, Vivek Kumar ; Lin, C.T. ; Keimer, B. ; Wolf, Th. ; Bernhard, Christian

In: The European Physical Journal - Special Topics, 2010, vol. 188, no. 1, p. 73-88

With the technique of infrared ellipsometry we performed a detailed study of the temperature- and doping dependence of the c-axis response of a series of YBa₂Cu₃O7−δ single crystals. In particular, we explored the anomalous electronic properties at temperatures above the macroscopic superconducting transition temperature, T c, whose conflicting...

Université de Fribourg

Evidence of a Precursor Superconducting Phase at Temperatures as High as 180 K in RBa₂Cu₃O7-δ (R=Y,Gd,Eu) Superconducting Crystals from Infrared Spectroscopy

Dubroka, Adam ; Rössle, Matthias ; Kim, Kyung Wan ; Malik, Vivek Kumar ; Munzar, Dominik ; Basov, D. N. ; Schafgans, A. A. ; Moon, S. J. ; Lin, C. T. ; Haug, D. ; Hinkov, V. ; Keimer, B. ; Wolf, Th. ; Storey, J. G. ; Tallon, Jeffery L. ; Bernhard, Christian

In: Physical Review Letters, 2011, vol. 106, no. 4, p. 047006

We show that a multilayer analysis of the infrared c-axis response of RBa₂Cu₃O7-δ (R=Y,Gd,Eu) provides important new information about the anomalous normal-state properties of underdoped cuprate high temperature superconductors. In addition to competing correlations which give rise to a pseudogap that depletes the low-energy electronic states below...

Université de Fribourg

Electronic Liquid Crystal State in the High-Temperature Superconductor YBa₂Cu₃O6.45

Hinkov, V. ; Haug, D. ; Fauqué, B. ; Bourges, P. ; Sidis, Y. ; Ivanov, A. ; Bernhard, Christian ; Lin, C. T. ; Keimer, B.

In: Science, 2008, vol. 319, p. 597-600

Electronic phases with symmetry properties matching those of conventional liquid crystals have recently been discovered in transport experiments on semiconductor heterostructures and metal oxides at millikelvin temperatures. We report the spontaneous onset of a one-dimensional, incommensurate modulation of the spin system in the high-transition-temperature superconductor...

Université de Fribourg

Evidence for spin-triplet superconducting correlations in metal-oxide heterostructures with noncollinear magnetization

Khaydukov, Yu. N. ; Ovsyannikov, G. A. ; Sheyerman, A. E. ; Constantinian, K. Y. ; Mustafa, L. ; Keller, T. ; Uribe-Laverde, Miguel Angel ; Kislinskii, Yu. V. ; Shadrin, A. V. ; Kalaboukhov, A. ; Keimer, B. ; Winkler, D.

In: Physical Review B, 2014, vol. 90, no. 3, p. 035130

Heterostructures composed of ferromagnetic La0.7Sr0.3MnO3, ferromagnetic SrRuO3, and superconducting YBa2Cu3O6+x were studied experimentally. Structures of composition Au/La0.7Sr0.3MnO3/SrRuO3/YBa2Cu3O6+x were prepared by pulsed laser deposition, and their high quality was confirmed by x-ray diffraction and reflectometry. A noncollinear magnetic state of the heterostructures was revealed by means...

Université de Fribourg

Granular superconductivity and charge/orbital order in YBa 2 Cu 3 O 7 /manganite trilayers

Khmaladze, Jarji ; Sarkar, Subhrangsu ; Soulier, Mathias ; Lyzwa, Fryderyk ; Prada, R. de Andres ; Perret, Edith ; Mallett, Benjamin P. P. ; Minola, M. ; Keimer, B. ; Bernhard, Christian

In: Physical Review Materials, 2019, vol. 3, no. 8, p. 084801

We studied how the electronic, superconducting, and magnetic properties of YBa2Cu3O7/Nd1−x(Ca1−ySry )xMnO3 multilayers depend on the tolerance factor and the hole doping of the manganite. In particular, we investigated the granular superconducting state and the related magnetic-field-driven insulator-to- superconductor transition that was previously discovered in corresponding multilayers...

Université de Fribourg

Competing interactions at the interface between ferromagnetic oxides revealed by spin-polarized neutron reflectometry

Kim, J.-H. ; Vrejoiu, I. ; Khaydukov, Y. ; Keller, T. ; Stahn, J. ; Rühm, A. ; Satapathy, Dillip Kumar ; Hinkov, V. ; Keimer, B.

In: Physical Review B - Condensed Matter and Materials Physics, 2012, vol. 86, no. 18, p. 180402

We have investigated the magnetization profiles in superlattices composed of the two ferromagnets La0.7Sr0.3MnO₃ and SrRuO₃ using spin-polarized neutron reflectometry. In combination with magnetometry, the neutron data indicate a noncollinear spin configuration where orientation of the Ru moments changes from in plane at the interface to out of plane deep inside the...