@article{ElsaesserSchieblMukhinetal.2017,
  author    = {Els{\"a}sser, S. and Schiebl, M. and Mukhin, A. A. and Balbashov, A. M. and Pimenov, A. and Geurts, J.},
  title     = {Impact of temperature-dependent local and global spin order in \(R\)MnO\(_3\) compounds for spin-phonon coupling and electromagnon activity},
  series = {New Journal of Physics},
  volume    = {19},
  journal   = {New Journal of Physics},
  doi       = {10.1088/1367-2630/aa55ed},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-171978},
  year      = {2017},
  abstract  = {The orthorhombic rare-earth manganite compounds \(R\)MnO\(_3\) show a global magnetic order for \(T\) < \(T\)\(_N\), and several representatives are multiferroic with a cycloidal spin ground state order for \(T\) < \(T\)\(_c\)\(_y\)\(_c\)\(_l\) < \(T\)\(_N\) \(\approx\) 40 K. We deduce from the temperature dependence of spin-phonon coupling in Raman spectroscopy for a series of \(R\)MnO\(_3\) compounds that their spin order locally persists up to about twice \(T\)\(_N\). Along the same line, our observation of the persistence of the electromagnon in GdMnO\(_3\) up to \(T\) \(\approx\) 100 K is attributed to a local cycloidal spin order for \(T\) > \(T\)\(_c\)\(_y\)\(_c\)\(_l\), in contrast to the hitherto assumed incommensurate sinusoidal phase in the intermediate temperature range. The development of the magnetization pattern can be described in terms of an order-disorder transition at \(T\)\(_c\)\(_y\)\(_c\)\(_l\) within a pseudospin model of localized spin cycloids with opposite chirality.},
  language  = {en}
}
@article{DziomShuvaevPimenovetal.2017,
  author    = {Dziom, V. and Shuvaev, A. and Pimenov, A. and Astakhov, G.V. and Ames, C. and Bendias, K. and B{\"o}ttcher, J. and Tkachov, G. and Hankiewicz, E.M. and Br{\"u}ne, C. and Buhmann, H. and Molenkamp, L.W.},
  title     = {Observation of the universal magnetoelectric effect in a 3D topological insulator},
  series = {Nature Communications},
  volume    = {8},
  journal   = {Nature Communications},
  number    = {15197},
  doi       = {10.1038/ncomms15197},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-170875},
  year      = {2017},
  abstract  = {The electrodynamics of topological insulators (TIs) is described by modified Maxwell's equations, which contain additional terms that couple an electric field to a magnetization and a magnetic field to a polarization of the medium, such that the coupling coefficient is quantized in odd multiples of α/4π per surface. Here we report on the observation of this so-called topological magnetoelectric effect. We use monochromatic terahertz (THz) spectroscopy of TI structures equipped with a semitransparent gate to selectively address surface states. In high external magnetic fields, we observe a universal Faraday rotation angle equal to the fine structure constant α=e\(^{2}\)/2E\(_{0}\)hc (in SI units) when a linearly polarized THz radiation of a certain frequency passes through the two surfaces of a strained HgTe 3D TI. These experiments give insight into axion electrodynamics of TIs and may potentially be used for a metrological definition of the three basic physical constants.},
  language  = {en}
}