Possible evidence for electromagnons in multiferroic manganites

Magnetodielectric materials are characterized by a strong coupling of magnetic and dielectric properties and in rare cases simultaneously exhibit both, magnetic and polar order. Among other multiferroics, TbMnO3 and GdMnO3 reveal a strong magneto-dielectric (ME) coupling and as a consequence fundamentally new spin excitations exist: Electro-active magnons, or electromagnons, i. e. spin waves which can be excited by ac electric fields. Here we show that these excitations appear in the phase with an incommensurate (IC) magnetic structure of the manganese spins. In external magnetic fields this IC structure can be suppressed and the electromagnons are wiped out, thereby inducing considerable changes in the index of refraction from dc up to THz frequencies. Hence, besides adding a new creature to the zoo of fundamental excitations, the refraction index can be tuned by moderate magnetic fields, which allows the design of a new generation of optical switches and optoelectronic devices.Comment: 4 Pages, 2 figure

Innate recognition of water bodies in echolocating bats

In the course of their lives, most animals must find different specific habitat and microhabitat types for survival and reproduction. Yet, in vertebrates, little is known about the sensory cues that mediate habitat recognition. In free flying bats the echolocation of insect-sized point targets is well understood, whereas how they recognize and classify spatially extended echo targets is currently unknown. In this study, we show how echolocating bats recognize ponds or other water bodies that are crucial for foraging, drinking and orientation. With wild bats of 15 different species (seven genera from three phylogenetically distant, large bat families), we found that bats perceived any extended, echo-acoustically smooth surface to be water, even in the presence of conflicting information from other sensory modalities. In addition, naive juvenile bats that had never before encountered a water body showed spontaneous drinking responses from smooth plates. This provides the first evidence for innate recognition of a habitat cue in a mammal

Bethe subalgebras of the group algebra of the symmetric group

We introduce families of maximal commutative subalgebras, called Bethe subalgebras, of the group algebra of the symmetric group. Bethe subalgebras are deformations of the Gelfand-Zetlin subalgebra. We describe various properties of Bethe subalgebras.Comment: AmsLaTeX, 32 pages; references update

High-frequency magnetic spectroscopy on the molecular magnetic cluster V-15

Vongtragool S, Gorshunov B, Mukhin AA, van Slageren J, Dressel M, Müller A. High-frequency magnetic spectroscopy on the molecular magnetic cluster V-15. PHYSICAL CHEMISTRY CHEMICAL PHYSICS. 2003;5(13):2778-2782.A novel type of high-frequency magnetic resonance spectroscopy was used to investigate magnetic excitations of the molecular magnetic cluster V-15 in the frequency range from 1.5 cm(-1) to 10 cm(-1), at low temperatures, between 2.5 K and 30 K. In the optical transmission spectra, we observed absorption lines over a wide range of magnetic fields up to 6.5 T, which correspond to the Zeeman splitting of the low-lying spin states. Our frequency-domain technique, and advanced data analysis allow accurate determination of the principal values of the anisotropic g tensor, and other mode parameters, even for powder samples. The g values were obtained as gparallel toc = 1.981 +/- 0.003 and g(perpendicular toc) = 1.953 +/- 0.003, while the intrinsic linewidth was found to be Deltanu = 0.02 - 0.035 cm(-1) ( 210 - 370 Oe). The temperature dependence of Deltamu, the mode contribution to the magnetic permeability, is in good agreement with theory

Frequency-domain magnetic resonance spectroscopy of molecular magnetic materials

van Slageren J, Vongtragool S, Gorshunov B, et al. Frequency-domain magnetic resonance spectroscopy of molecular magnetic materials. PHYSICAL CHEMISTRY CHEMICAL PHYSICS. 2003;5(18):3837-3843.A brief review is presented of a novel method of high-frequency magnetic resonance spectroscopy, which sweeps the frequency at a fixed magnetic field, including zero field. We describe the main features of this frequency-domain spectrometer which works in the spectral range from 30 GHz to 1.5 THz and at magnetic fields up to 8 T; the temperature can be as low as 0.4 K. The versatility of this technique is demonstrated by means of a number of examples from the field of molecular magnetism

Multifunctional sensing with hybrid nanophotonic structures

\u3cp\u3eThe development of multifunctional systems for investigation of different parameters involved in chemical reactions is a vital problem in case of low concentrations of tested matter. Here, we investigate hybrid plasmonic-dielectric system and demonstrate possibility of such application for multifunctional sensing.\u3c/p\u3