title: Ultrafast angular momentum transfer in multisublattice ferrimagnets.
abstract: Femtosecond laser pulses can be used to induce ultrafast changes of the magnetization in magnetic materials. However, one of the unsolved questions is that of conservation of the total angular momentum during the ultrafast demagnetization. Here we report the ultrafast transfer of angular momentum during the first hundred femtoseconds in ferrimagnetic Co0.8Gd0.2 and Co0.74Tb0.26 films. Using time-resolved X-ray magnetic circular dichroism allowed for time-resolved determination of spin and orbital momenta for each element. We report an ultrafast quenching of the magnetocrystalline anisotropy and show that at early times the demagnetization in ferrimagnetic alloys is driven by the local transfer of angular momenta between the two exchange-coupled sublattices while the total angular momentum stays constant. In Co0.74Tb0.26 we have observed a transfer of the total angular momentum to an external bath, which is delayed by ~150 fs.
authors.affiliation: Institut de Physique et de Chimie des Matériaux de Strasbourg, UMR7504, CNRS et Université de Strasbourg, 67034 Strasbourg, France.
authors.forename: N
authors.initials: N
authors.lastname: Bergeard
authors.affiliation: Institut de Physique et de Chimie des Matériaux de Strasbourg, UMR7504, CNRS et Université de Strasbourg, 67034 Strasbourg, France.
authors.forename: V
authors.initials: V
authors.lastname: López-Flores
authors.affiliation: Institut de Physique et de Chimie des Matériaux de Strasbourg, UMR7504, CNRS et Université de Strasbourg, 67034 Strasbourg, France.
authors.forename: V
authors.initials: V
authors.lastname: Halté
authors.affiliation: Institut Jean Lamour, Université Henri Poincaré, UMR 7198, 54506 Nancy, France.
authors.forename: M
authors.initials: M
authors.lastname: Hehn
authors.affiliation: 1] Department of Materials, ETH Zürich, CH-8093 Zürich, Switzerland [2] Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein Strasse 15, 12489 Berlin, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Stamm
authors.affiliation: Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein Strasse 15, 12489 Berlin, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Pontius
authors.affiliation: Institut de Physique et de Chimie des Matériaux de Strasbourg, UMR7504, CNRS et Université de Strasbourg, 67034 Strasbourg, France.
authors.forename: E
authors.initials: E
authors.lastname: Beaurepaire
authors.affiliation: Institut de Physique et de Chimie des Matériaux de Strasbourg, UMR7504, CNRS et Université de Strasbourg, 67034 Strasbourg, France.
authors.forename: C
authors.initials: C
authors.lastname: Boeglin
mesh_terms: D000497:Alloys / Q000737:chemistry*; D016880:Anisotropy; D002942:Circular Dichroism / Q000379:methods; D003035:Cobalt / Q000737:chemistry; D003460:Crystallization; D005682:Gadolinium / Q000737:chemistry; D060328:Magnetic Phenomena; D059346:Magnets / Q000737:chemistry*; D013725:Terbium / Q000737:chemistry; D013816:Thermodynamics; D014965:X-Rays
chemical_list: D000497:Alloys; D013725:Terbium; D003035:Cobalt; D005682:Gadolinium