title: Ultrafast optical tuning of ferromagnetism via the carrier density.
abstract: Interest in manipulating the magnetic order by ultrashort laser pulses has thrived since it was observed that such pulses can be used to alter the magnetization on a sub-picosecond timescale. Usually this involves demagnetization by laser heating or, in rare cases, a transient increase of magnetization. Here we demonstrate a mechanism that allows the magnetic order of a material to be enhanced or attenuated at will. This is possible in systems simultaneously possessing a low, tunable density of conduction band carriers and a high density of magnetic moments. In such systems, the thermalization time can be set such that adiabatic processes dominate the photoinduced change of the magnetic order--the three-temperature model for interacting thermalized electron, spin and lattice reservoirs is bypassed. In ferromagnetic Eu(1-x)Gd(x)O, we thereby demonstrate the strengthening as well as the weakening of the magnetic order by ~10% and within ≤3 ps by optically controlling the magnetic exchange interaction.
authors.affiliation: 1] Department of Physics, Tohoku University, Sendai 980-8578, Japan [2] Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 4, 8093 Zurich, Switzerland.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Matsubara
authors.affiliation: Physikalisches Institut, Universität Bonn, Nussallee 12, 53115 Bonn, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Schroer
authors.affiliation: Institut für Physik, Universität Augsburg, 86135 Augsburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schmehl
authors.affiliation: Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853-1501, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Melville
authors.affiliation: Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 4, 8093 Zurich, Switzerland.
authors.forename: Carsten
authors.initials: C
authors.lastname: Becher
authors.affiliation: Physikalisches Institut, Universität Bonn, Nussallee 12, 53115 Bonn, Germany.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Trujillo-Martinez
authors.affiliation: 1] Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853-1501, USA [2] Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853-1501, USA.
authors.forename: Darrell G
authors.initials: DG
authors.lastname: Schlom
authors.affiliation: Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Mannhart
authors.affiliation: Physikalisches Institut, Universität Bonn, Nussallee 12, 53115 Bonn, Germany.
authors.forename: Johann
authors.initials: J
authors.lastname: Kroha
authors.affiliation: Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 4, 8093 Zurich, Switzerland.
authors.forename: Manfred
authors.initials: M
authors.lastname: Fiebig