Université de Fribourg

Structural, magnetic and electronic properties of pulsed-laser-deposition grown SrFeO 3− δ thin films and SrFeO 3− δ /La 2/3 Ca 1/3 MnO 3 multilayers

Perret, Edith ; Sen, Kaushik ; Khmaladze, Jarji ; Mallett, Benjamin P. P. ; Yazdi-Rizi, Meghdad ; Maršík, Premysl ; Das, Saikat ; Marozau, Ivan ; Uribe-Laverde, Miguel Angel ; Andrés Prada, R. de ; Strempfer, J. ; Döbeli, Max ; Biškup, N. ; Varela, M. ; Mathis, Y.-L. ; Bernhard, Christian

In: Journal of Physics: Condensed Matter, 2017, vol. 29, no. 49, p. 495601

We studied the structural, magnetic and electronic properties of ${\rm SrFeO}_{3- \delta}$ (SFO) thin films and ${\rm SrFeO}_{3-\delta}$ /${\rm La}_{2/3}$ ${\rm Ca}_{1/3}$ MnO3 (LCMO) superlattices that have been grown with pulsed laser deposition (PLD) on ${\rm La}_{0.3}$ ${\rm Sr}_{0.7}$ ${\rm Al}_{0.65}$ ${\rm Ta}_{0.35}$ ${\rm O}_{3}$ (LSAT) substrates. X-ray reflectometry and scanning ...

Université de Fribourg

Electric-Field-Induced Polar Order and Localization of the Confined Electrons in LaAlO₃/SrTiO₃ Heterostructures

Rössle, Matthias ; Kim, Kyung Wan ; Dubroka, Adam ; Maršík, Premysl ; Wang, Chen Nan ; Jany, R. ; Richter, C. ; Mannhart, J. ; Schneider, C. W. ; Frano, A. ; Wochner, P. ; Lu, Y. ; Keimer, B. ; Shukla, D. K. ; Strempfer, J. ; Bernhard, Christian

In: Physical Review Letters, 2013, vol. 110, no. 13, p. 136805

With ellipsometry, x-ray diffraction, and resistance measurements we investigated the electric-field effect on the confined electrons at the LaAlO₃/SrTiO₃ interface. We obtained evidence that the localization of the electrons at negative gate voltage is induced, or at least enhanced, by a polar phase transition in SrTiO₃ which strongly reduces the lattice polarizability and the subsequent...

Université de Fribourg

Optical response of ferromagnetic YTiO₃ studied by spectral ellipsometry

Kovaleva, N. N. ; Boris, A. V. ; Yordanov, P. ; Maljuk, A. ; Brücher, E. ; Strempfer, J. ; Konuma, M. ; Zegkinoglou, I. ; Bernhard, Christian ; Stoneham, A. M. ; Keimer, B.

In: Physical Review B: Condensend Matter and Materials Physics, 2007, vol. 76, no. 15, p. 155125

We have studied the temperature dependence of spectroscopic ellipsometry spectra of an electrically insulating, nearly stoichiometric YTiO₃ single crystal with ferromagnetic Curie temperature TC=30 K. The optical response exhibits a weak but noticeable anisotropy. Using a classical dispersion analysis, we identify three low-energy optical bands at 2.0, 2.9, and 3.7 eV....

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...