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Université de Fribourg

Strain-induced ferromagnetism in antiferromagnetic LuMnO₃ thin films

White, J. S. ; Bator, M. ; Hu, Yanqing ; Luetkens, H. ; Stahn, J. ; Capelli, S. ; Das, Saikat ; Döbeli, M. ; Lippert, Th. ; Malik, Vivek Kumar ; Martynczuk, J. ; Wokaun, A. ; Kenzelmann, M. ; Niedermayer, Ch. ; Schneider, C. W.

In: Physical Review Letters, 2013, vol. 111, no. 3, p. 037201

Single phase and strained LuMnO₃ thin films are discovered to display coexisting ferromagnetic and antiferromagnetic orders. A large moment ferromagnetism (≈1μB), which is absent in bulk samples, is shown to display a magnetic moment distribution that is peaked at the highly strained substrate-film interface. We further show that the strain-induced ferromagnetism and the...

Université de Fribourg

Depth profile of the ferromagnetic order in a YBa₂Cu₃O₇/La2/3Ca1/3MnO₃ superlattice on a LSAT substrate: A polarized neutron reflectometry study

Uribe-Laverde, Miguel Angel ; Satapathy, Dillip Kumar ; Marozau, Ivan ; Malik, Vivek Kumar ; Das, Saikat ; Sen, Kaushik ; Stahn, J. ; Rühm, A. ; Kim, Joo Young ; Keller, T. ; Devishvili, A. ; Toperverg, B. P. ; Bernhard, Christian

In: Physical Review B - Condensed Matter and Materials Physics, 2013, vol. 87, no. 11, p. 115105

Using polarized neutron reflectometry (PNR) we have investigated a [YBa₂Cu₃O₇(10 nm)/La2/3Ca1/3MnO₃(9 nm)]₁₀ (YBCO/LCMO) superlattice grown by pulsed laser deposition on a La0.3Sr0.7Al0.65Ta0.35O₃ (LSAT) substrate. Due to the high structural quality of the superlattice and the substrate, the specular reflectivity...

Université de Fribourg

Spatially resolved strain-imprinted magnetic states in an artificial multiferroic

Chopdekar, R. V. ; Malik, Vivek Kumar ; Rodríguez, A. Fraile ; Guyader, L. Le ; Takamura, Y. ; Scholl, A. ; Stender, D. ; Schneider, C. W. ; Bernhard, Christian ; Nolting, F. ; Heyderman, L. J.

In: Physical Review B - Condensed Matter and Materials Physics, 2012, vol. 86, no. 01, p. 014408

Artificial multiferroic systems, in which novel properties can emerge from elastic coupling between piezoelectric and magnetostrictive phases, are a promising route to obtain significant room-temperature magnetoelectric coupling at the nanoscale. In this work, we have used element-specific soft x-ray photoemission electron microscopy to spatially resolve the effects of ferroelectric BaTiO₃ on...

Université de Fribourg

Pulsed laser deposition growth of heteroepitaxial YBa2Cu3O7/La0.67Ca0.33MnO3 superlattices on NdGaO3 and Sr0.7La0.3Al0.65Ta0.35O3 substrates

Malik, Vivek Kumar ; Marozau, I. ; Das, S. ; Doggett, B. ; Satapathy, Dillip Kumar ; Uribe-Laverde, M. A. ; Biskup, N. ; Varela, M. ; Schneider, C. W. ; Marcelot, C. ; Stahn, J. ; Bernhard, Christian

In: Physical Review B - Condensed matter and materials physics, 2012, vol. 85, no. 5, p. 054514

Heteroepitaxial superlattices of [YBa₂Cu₃O₇(n)/La0.67Ca0.33MnO₃(m)]x (YBCO/LCMO), where n and m are the number of YBCO and LCMO monolayers and x the number of bilayer repetitions, have been grown with pulsed laser deposition on NdGaO₃ (110) and Sr0.7La0.3Al0.65Ta0.35O₃ (001). These substrates are well lattice...

Université de Fribourg

Magnetism, superconductivity, and coupling in cuprate heterostructures probed by low-energy muon-spin rotation

Wojek, B. M. ; Morenzoni, E. ; Eshchenko, D. G. ; Suter, A. ; Prokscha, T. ; Keller, H. ; Koller, E. ; Fischer, Ø. ; Malik, Vivek Kumar ; Bernhard, Christian ; Döbeli, M.

In: Physical Review B - Condensed matter and materials physics, 2012, vol. 85, no. 2, p. 024505

We present a low-energy muon-spin-rotation study of the magnetic and superconducting properties of YBa₂Cu₃O7−δ/PrBa₂Cu₃O7−δ trilayer and bilayer heterostructures. By determining the magnetic-field profiles throughout these structures, we show that a finite superfluid density can be induced in otherwise semiconducting PrBa₂Cu₃O7−δ layers...

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

Engineering spin propagation across a hybrid organic/inorganic interface using a polar layer

Schulz, Leander ; Nuccio, L. ; Willis, M. ; Desai, P. ; Shakya, P. ; Kreouzis, T. ; Malik, Vivek Kumar ; Bernhard, Christian ; Pratt, F. L. ; Morley, N. A. ; Suter, A. ; Nieuwenhuys, G. J. ; Prokscha, T. ; Morenzoni, E. ; Gillin, W. P. ; Drew, Alan J.

In: Nature Materials, 2011, vol. 10, p. 39–44

Spintronics has shown a remarkable and rapid development, for example from the initial discovery of giant magnetoresistance in spin valves (Baibich, M. N. et al. Giant magnetoresistance of (001)Fe/(001)Cr magnetic superlattices. Phys. Rev. Lett. 61, 2472–2475, 1988) to their ubiquity in hard-disk read heads in a relatively short time. However, the ability to fully harness electron spin as...

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

Magnetic properties of silica coated spindle-type hematite particles

Reufer, Mathias ; Dietsch, Hervé ; Gasser, Urs ; Grobéty, Bernard ; Hirt, A. M. ; Malik, Vivek Kumar ; Schurtenberger, Peter

In: Journal of Physics: Condensed Matter, 2011, vol. 23, no. 6, p. 065102

Magnetic properties of particles are generally determined from randomly oriented ensembles and the influence of the particle orientation on the magnetic response is neglected. Here, we report on the magnetic characterization of anisotropic spindle- type hematite particles. The easy axis of magnetization is within the basal plane of hematite, which is oriented perpendicular to the spindle axis....

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...