Temperature-dependent spin-wave behavior in Co/CoO bilayers studied by Brillouin light scattering

Ercole, Ari; Lew, Wen Siang; Lauhoff, G.; Kernohan, E. T. M.; Lee, J.; Bland, J. A. C.

doi:10.1103/physrevb.62.6429

Cited by 29 publications

(30 citation statements)

References 38 publications

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“…The excitation linewidths are as much as a factor of four larger in the nanoscaled CoO than in the bulk. Similar excess broadening has previously been observed for the precessional mode in both ferromagnetic and antiferromagnetic nanoparticles 77 and thin films 24,78 . It is explained by acknowledging that the lifetime of the q=0 spin wave is limited by its decay via scattering into spin wave modes with q =0, and not by the spin-lattice relaxation time, which is known to be much longer [79][80][81] .…”

Section: Discussionsupporting

confidence: 85%

“…Below a characteristic blocking temperature T B , there is insufficient thermal energy in equilibrium to completely reverse the nanoparticle moment, which instead precesses in the presence of internal or external fields. The precession mode can be considered a q=0 spin wave, and its energies and lifetimes in different types of nanoscaled systems have been studied using inelastic neutron scattering 14,16,[18][19][20][21] , as well as Brillouin scattering [22][23][24][25][26] and ferromagnetic resonance experiments 25,27,28 . Precession modes have been studied in both ferromagnetic and antiferromagnetic nanoparticles, where the field in the latter case couples to the net moment of unterminated surface spins.…”

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confidence: 99%

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Low-energy magnetic excitations in Co/CoO core/shell nanoparticles

et al. 2011

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We have used inelastic neutron scattering measurements to study the magnetic excitations of Co core/CoO shell nanoparticles for energies from 0-50 meV. Above the blocking temperature TB, broad quasielastic scattering is observed, corresponding to the reorientation of the Co core moments and to paramagnetic CoO scattering. Below TB, two nearly dispersionless inelastic peaks are found, whose energies increase with decreasing temperature as order parameters, controlled by the nanoparticle Néel temperature TN =235 K, and saturating as T→0 at 2.7 meV and 6.7 meV, respectively. Similar excitations were observed in a powdered single crystal of CoO, indicating that both are intrinsic excitations of CoO, resulting from the exchange splitting of single ion states for T≤TN . Pronounced finite size effects are observed for the scattering from the CoO nanoparticle shells, whose thicknesses range from 1.7-4.5 nm. These include an enhanced excitation linewidth, as well as a response that is not only spread over a much wider range of wave vectors, but is also significantly more intense in the nanoparticles than in bulk CoO.

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Section: Discussionsupporting

confidence: 85%

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confidence: 99%

Low-energy magnetic excitations in Co/CoO core/shell nanoparticles

et al. 2011

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“…Most of the experimental studies use natural oxidation or in-situ thermal oxidation of Co, resulting in a CoO top layer of about 25 Å. 1,[19][20][21][22][23] Thicker monocrystalline CoO can be achieved by reactive sputtering, [24][25][26][27] magnetron sputtering techniques, 28 or by evaporating Co in O atmosphere by molecular beam epitaxy ͑MBE͒.…”

Section: Introductionmentioning

confidence: 99%

Structural and magnetic properties of stoichiometric epitaxialCoO∕Feexchange-bias bilayers

et al. 2007

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We present a detailed study of the magnetic and structural properties of the CoO/ Fe bilayers by using a combination of x-ray diffraction ͑crystalline structure͒, Rutherford backscattering ͑chemical composition͒, and SQUID magnetometry ͑magnetic characterization͒ measurements. We prepared stoichiometric and single crystalline CoO thin films by a post-deposition annealing process in ultrahigh-vacuum conditions from sputter deposited hyperstoichiometric, polycrystalline CoO films. A simultaneous increase of the CoO crystalline quality and chemical phase purity has been achieved. Subsequently, the annealed CoO layers served as a template for the growth of epitaxial Fe films. The epitaxial relation between CoO and Fe was found to be of the Nishiyama-Wassermann type, where the Fe͓001͔ direction is parallel aligned to the CoO͓1-10͔ direction. The magnetic properties of CoO/ Fe bilayers are strongly influenced by the stoichiometry of the antiferromagnetic CoO layer. Especially the blocking temperature is sensitive to the oxygen concentration within the CoO layer. While the blocking temperature of stoichiometric, epitaxial CoO/ Fe exchange-bias bilayers almost equals the Néel temperature of bulk CoO, it is strongly reduced for superstoichiometric, polycrystalline CoO.

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“…Several experimental and theoretical studies were carried out to understand the origin of the various interactions existing in this kind of systems, in particular in the interface since it presents magnetic properties different from those of the bulk [1][2][3]. In this paper, we studied the magnon contribution to the magnetic properties of [Fe/Cu] and [Ni/Cu] simple superlattices and of [Ni 1Àx Fe x /Cu] alloy super-lattices for xp0:2.…”

Section: Introductionmentioning

confidence: 97%