5 research outputs found
Direct observation of Oersted-field-induced magnetization dynamics in magnetic nanostripes
We have used time-resolved x-ray photoemission electron microscopy to
investigate the magnetization dynamics induced by nanosecond current pulses in
NiFe/Cu/Co nanostripes. A large tilt of the NiFe magnetization in the direction
transverse to the stripe is observed during the pulses. We show that this
effect cannot be quantitatively understood from the amplitude of the Oersted
field and the shape anisotropy. High frequency oscillations observed at the
onset of the pulses are attributed to precessional motion of the NiFe
magnetization about the effective field. We discuss the possible origins of the
large magnetization tilt and the potential implications of the static and
dynamic effects of the Oersted field on current-induced domain wall motion in
such stripes.Comment: Published in Phys. Rev. B 83, 020406 (2011) (Rapid Communications
Exploring the limits of soft x-ray magnetic holography: Imaging magnetization reversal of buried interfaces (invited)
The following article appeared in Journal of Applied Physics 109.7 (2011): 07D357 and may be found at http://scitation.aip.org/content/aip/journal/jap/109/7/10.1063/1.3567035Only a very few experimental techniques can address the microscopic magnetization reversal behavior of the different magnetic layers in a multilayered system with element selectivity. We present an element-selective study of ferromagnetic (FM) [Co/Pt]n multilayers with perpendicular anisotropy exchange-coupled to antiferromagnetic (AFM) FeMn and IrMn films performed with a new experimental set-up developed for both soft x-ray spectroscopy and holography imaging purposes. The spectroscopy analysis allows the quantification of the unpinned (pinned) uncompensated AFM moments, providing direct evidence of its parallel (antiparallel) alignment with respect to the FM moments. The holography experiments give a direct view of both FM and uncompensated AFM magnetic structures, showing that they replicate to each other during magnetization reversal. Remarkably, we show magnetic images for effective thicknesses as small as one monolayer. Our results provide new microscopic insights into the exchange coupling phenomena and explore the sensitivity limits of these techniques. Future trends are also discussed.We acknowledge technical support by the ESRF staff R. Barrett, R. Homs-Regojo, T. Trenit, and G. Retout. A. B. acknowledges support through a Ramo´n y Cajal contract from the Spanish MICINN. This work was supported in part by the Spanish MICINN through Projects CSD2007-00010, and MAT2010-21822 and by Comunidad de Madrid through Project S2009/MAT-1726.Comunidad de Madrid. S2009/MAT-1726/NANOBIOMAGNE
High domain wall velocity at zero magnetic field induced by low current densities in spin-valve nanostripes
Current-induced magnetic domain wall motion at zero magnetic field is
observed in the permalloy layer of a spin-valve-based nanostripe using
photoemission electron microscopy. The domain wall movement is hampered by
pinning sites, but in between them high domain wall velocities (exceeding 150
m/s) are obtained for current densities well below 10^{12} \unit{A/m^2},
suggesting that these trilayer systems are promising for applications in domain
wall devices in case of well controlled pinning positions. Vertical spin
currents in these structures provide a potential explanation for the increase
in domain wall velocity at low current densities.Comment: Published version, Applied Physics Express 2, 023003 (2009)
http://dx.doi.org/10.1143/APEX.2.02300
Imaging and quantifying perpendicular exchange biased systems by soft x-ray holography and spectroscopy
International audienc
Current-induced motion and pinning of domain walls in spin-valve nanowires studied by XMCD-PEEM
International audienceVery large average velocities, up to 600 m/s, have been found for domain-wall motion driven by 3-ns-long pulses of electric current in zero magnetic field in the NiFe layer of 200-nm-wide NiFe/Cu/Co nanowires. For longer pulses, the domain-wall motion is strongly hindered by pinning potentials. Dipolar interactions between the NiFe and Co layers caused by anisotropy inhomogeneities have been identified as the most important among the different potential sources of DW pinning. The domain-wall velocities increase with current density, but a substantial drop is observed at current densities above 4×10^11 A/m