title: Colossal Terahertz Magnetoresistance at Room Temperature in Epitaxial La0.7Sr0.3MnO3Nanocomposites and Single-Phase Thin Films.
abstract: Colossal magnetoresistance (CMR) is demonstrated at terahertz (THz) frequencies by using terahertz time-domain magnetospectroscopy to examine vertically aligned nanocomposites (VANs) and planar thin films of La0.7Sr0.3MnO3. At the Curie temperature (room temperature), the THz conductivity of the VAN was dramatically enhanced by over 2 orders of magnitude under the application of a magnetic field with a non-Drude THz conductivity that increased with frequency. The direct current (dc) CMR of the VAN is controlled by extrinsic magnetotransport mechanisms such as spin-polarized tunneling between nanograins. In contrast, we find that THz CMR is dominated by intrinsic, intragrain transport: the mean free path was smaller than the nanocolumn size, and the planar thin-film exhibited similar THz CMR to the VAN. Surprisingly, the observed colossal THz magnetoresistance suggests that the magnetoresistance can be large for alternating current motion on nanometer length scales, even when the magnetoresistance is negligible on the macroscopic length scales probed by dc transport. This suggests that colossal magnetoresistance at THz frequencies may find use in nanoelectronics and in THz optical components controlled by magnetic fields. The VAN can be scaled in thickness while retaining a high structural quality and offers a larger THz CMR at room temperature than the planar film.
authors.affiliation: Department of Physics, University of Warwick , Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom.
authors.forename: J
authors.identifier: 0000-0002-9680-0138
authors.initials: J
authors.lastname: Lloyd-Hughes
authors.affiliation: Department of Physics, University of Warwick , Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom.
authors.forename: C D W
authors.initials: CD
authors.lastname: Mosley
authors.affiliation: Department of Physics, Clarendon Laboratory, University of Oxford , Parks Road, Oxford, OX1 3PU, United Kingdom.
authors.forename: S P P
authors.initials: SP
authors.lastname: Jones
authors.affiliation: Department of Physics, University of Warwick , Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom.
authors.forename: M R
authors.initials: MR
authors.lastname: Lees
authors.affiliation: Center for Integrated Nanotechnologies, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: A
authors.identifier: 0000-0003-2639-2797
authors.initials: A
authors.lastname: Chen
authors.affiliation: Materials Design and Innovation, School of Engineering and Applied Sciences, University at Buffalo , 311 Bell Hall, Buffalo, New York 14260-5030, United States.
authors.forename: Q X
authors.initials: QX
authors.lastname: Jia
authors.affiliation: Department of Materials Science, University of Cambridge , 27 Charles Babbage Road, Cambridge, CB3 0FS, United Kingdom.
authors.forename: E-M
authors.initials: EM
authors.lastname: Choi
authors.affiliation: Department of Materials Science, University of Cambridge , 27 Charles Babbage Road, Cambridge, CB3 0FS, United Kingdom.
authors.forename: J L
authors.initials: JL
authors.lastname: MacManus-Driscoll
keywords: Perovskite oxides; colossal magnetoresistance; conductivity; oxide nanocomposites; terahertz radiation