title: Femtosecond dynamics of the collinear-to-spiral antiferromagnetic phase transition in CuO.
abstract: We report on the ultrafast dynamics of magnetic order in a single crystal of CuO at a temperature of 207 K in response to strong optical excitation using femtosecond resonant x-ray diffraction. In the experiment, a femtosecond laser pulse induces a sudden, nonequilibrium increase in magnetic disorder. After a short delay ranging from 400 fs to 2 ps, we observe changes in the relative intensity of the magnetic ordering diffraction peaks that indicate a shift from a collinear commensurate phase to a spiral incommensurate phase. These results indicate that the ultimate speed for this antiferromagnetic reorientation transition in CuO is limited by the long-wavelength magnetic excitation connecting the two phases.
authors.affiliation: Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: S L
authors.initials: SL
authors.lastname: Johnson
authors.forename: R A
authors.initials: RA
authors.lastname: de Souza
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authors.lastname: Beaud
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authors.lastname: Möhr-Vorobeva
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authors.lastname: Schlotter
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authors.lastname: Krupin
authors.forename: W-S
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authors.lastname: Lee
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authors.lastname: Chuang
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authors.lastname: Patthey
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authors.lastname: Lu
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authors.initials: PS
authors.lastname: Kirchmann
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authors.lastname: Trigo
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authors.lastname: Denes
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authors.initials: D
authors.lastname: Doering
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authors.lastname: Hussain
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authors.initials: ZX
authors.lastname: Shen
authors.forename: D
authors.initials: D
authors.lastname: Prabhakaran
authors.forename: A T
authors.initials: AT
authors.lastname: Boothroyd