[{"type":"speech","title":"Strain induced ferromagnetic order in undoped LaCoO\u2083 thin films","issued":{"date-parts":[["2007"]]},"author":[{"family":"Fuchs","given":"D."},{"family":"Pinta","given":"C."},{"family":"Schwarz","given":"T."},{"family":"Schweiss","given":"P."},{"family":"Nagel","given":"P."},{"family":"Schuppler","given":"S."},{"family":"Schneider","given":"R."},{"family":"Merz","given":"M."},{"family":"Roth","given":"G."},{"family":"L\u00f6hneysen","given":"H. von"}],"note":"71.Jahrestagung der Deutschen Physikalischen Gesellschaft und DPG Fr\u00fchjahrstagung des Arbeitskreises Festk\u00f6rperphysik, Fachverband Magnetismus, Regensburg, 26.-30.M\u00e4rz 2007 Verhandlungen der Deutschen Physikalischen Gesellschaft, R.6, B.42(2007) MA 25.2","abstract":"Section Magnetism (MA)\nThursday\noretical work the spin-dynamics and the switching properties of a\nmagnetic nanoparticles (Stoner-particles) using the Landau-LifshitzGilbert equation extended for the case of \ufb01nite temperatures, a task\nwhich has not been tacked by previous studies [2]. In particular, we\nare interested in the minimal amplitudes of the switching \ufb01elds and the\ncorresponding reversal times of the magnetic moment of the nanoparticle both for static and time-dependent external \ufb01elds depending on\nthe damping. Optimal parameters for the magnetization reversal and\ntheir temperature dependence are worked out.\nReferences:\n[1] C. Thirion, W. Wernsdorfer and D. Mailly, Nat. Mater. 2, 524\n(2003).\n[2] Z. Z. Sun and X. R. Wang, Phys. Rev. Lett. 97, 077205 (2006).\nMA 24.9\nThu 12:15\nH23\nSpin transfer induced magnetization dynamics using the\nAg\/Fe(100) interface \u2014 \u2022Ronald Lehndorff, Daniel E.\n\u00a8\nBurgler, and Claus M. Schneider \u2014 Institut f\u00a8r Festk\u00a8rperu\nforschung and cni - Center of Nanoelectronic Systems for Information\nSpin-polarized currents in magnetic nanostructures induce magnetization dynamics, which di\ufb00er strongly from magnetic \ufb01eld induced\ndynamics [1, 2]. The Ag\/Fe(100) interface has been predicted to have\na strong spin dependence of the interface resistance and should therefore be a good spin polarizer [3] and give strong spin transfer e\ufb00ects.\nWe study spin transfer induced magnetization dynamics in singlecrystalline, layered systems grown by molecular beam epitaxy. The\nlayer sequence is 2 nm Fe\/ 6 nm Ag\/ 20 nm Fe. The topmost layer is\nstructured by e-beam lithography and ion beam etching into a circle\nof 65 to 85 nm in diameter. To characterize the structures we measure\nthe current-perpendicular-plane giant magnetoresistance. Current induced switching and current driven high-frequency excitations of the\nfree layer are recorded under di\ufb00erent angles of the magnetic \ufb01eld with\nrespect to the crystal axes of the Fe(100) layers.\n[1] J.C. Slonczewski, J. Magn. Magn. Mater. 159, L1 (1996)\n[2] L. Berger, Phys. Rev. B 54, 9353 (1996)\n[3] D. Stiles, A. Zangwill, Phys. Rev. B 66, 014407 (2002)\nMA 24.10\nThu 12:30\nH23\nFerromagnetic resonance study of the interlayer exchange\ncoupled NiFe\/Ru\/NiFe \ufb01lms \u2014 \u2022Mohamed Belmeguenai, To\u00a8\nbias Martin, Georg Woltersdorf, and Gunther Bayreuther \u2014\nInstitut f\u00a8r Experimentelle und Angewandte Physik, Universit\u00a8t Reu\nFerromagnetic bilayers exchange coupled through a non-magnetic\nmetallic layer are used in magnetic recording devices. Their dynamics at 1 to 10 GHz which present a fundamental limit to increasing\ndata rates have been studied in this work. We used conventional\nferromagnetic resonance (FMR) and vector network analyzer FMR\nto study the di\ufb00erent excited dynamic modes in exchange coupled\nSi\/Ta\/NiFe(30 nm)\/Ru(dRu)\/NiFe(30 nm)\/Ta \ufb01lms with variable Ru\nthicknesses dRu. The interlayer exchange coupling (IEC) constants are\ndetermined by VSM and MOKE. The dynamic measurements show the\nexistence of an optic and an acoustic precession mode. Their resonance\nfrequencies and therefore the IEC are found to oscillate as a function\nof dRu with a period of 8.5 \u02da. The frequency oscillations of the opA\ntic mode are coupling-dependent while those of the acoustic mode are\nindirectly related to coupling via the canting angle of the layer magnetizations. The FMR measurements carried out at 22 and 35 GHz\nrevealed clearly di\ufb00erent behaviors of the FMR linewidths as a function\nof dRu for the optic and acoustic modes and we observed perpendicular standing spin-waves. The FMR linewidth of the di\ufb00erent excited\nmodes increases with the microwave frequencies and typical damping\nconstants of 0.0073 have been measured.\nTime: Thursday 14:00\u201315:00\nInvited Talk\nLocation: H10\nMA 25.1\nThu 14:00\nH10\nbr\u00a8cken\n\u201d\nInvited Talk\nMA 25.2\nThu 14:30\nH10\nStrain induced ferromagnetic order in undoped LaCoO3\nthin \ufb01lms \u2014 \u2022Dirk Fuchs1 , Christian Pinta1,2 , Thorsten\nRudolf Schneider1 , Michael Merz3 , Georg Roth3 , and Hilbert\n\u00a8\nversit\u00a8t Karlsruhe, 76128 Karlsruhe \u2014 3 Institut f\u00a8 r Kristallographie,\nDespite the well established nonmagnetic low spin (S = 0) ground state\nof LaCoO3 there are many publications reporting on the existence of\neither long- or short-range ferromagnetic order. For example, Yan et\nal.[1] have found a ferromagnetic component with a Tc = 85 K and\nhave suggested a ferromagnetic coupling of surface cobalt atoms. In\nthe presence of the con\ufb02icting results the origin of the observed ferromagnetism in LaCoO3 is still a challenging question and motivated\nthis work. In order to scrutinize the proposed surface ferromagnetism\nby Yan et al. we have carried out experiments on thin \ufb01lms prepared by\npulsed laser deposition which inherently show an extremely large surface\/volume ratio. In contrast to polycrystalline LaCoO3 \ufb01lms which\ndid not show ferromagnetism down to T = 5 K epitaxial \ufb01lms with the\nsame surface\/volume ratio showed clear ferromagnetic order at Tc =\n85 K. We discuss this surprising result in terms of ferromagnetic order\ninduced by epitaxial strain.\n[1] J. Q. Yan et al., Phys. Rev. B 70, 014402, (2004).","kit-publication-id":"230067454"}]