58 research outputs found
Selection Rules for All-Optical Magnetic Recording in Iron Garnet
Finding an electronic transition a subtle excitation of which can launch
dramatic changes of electric, optical or magnetic properties of media is one of
the long-standing dreams in the field of photo-induced phase transitions [1-5].
Therefore the discovery of the magnetization switching only by a femtosecond
laser pulse [6-10] triggered intense discussions about mechanisms responsible
for these laser-induced changes. Here we report the experimentally revealed
selection rules on polarization and wavelengths of ultrafast photo-magnetic
recording in Co-doped garnet film and identify the workspace of the parameters
(magnetic damping, wavelength and polarization of light) allowing this effect.
The all-optical magnetic switching under both single pulse and multiple-pulse
sequences can be achieved at room temperature, in narrow spectral ranges with
light polarized either along or crystallographic axes of the
garnet. The revealed selection rules indicate that the excitations responsible
for the coupling of light to spins are d-electron transitions in octahedral and
tetrahedral Co-sublattices, respectively
Coherent control of photomagnetic back-switching by double-pump laser pulses
The control of nonthermal, all-optical magnetization switching under the
regime with an independent state of laser polarization opens up new
opportunities for ultrafast magnetic recording. Here, we investigate the
photo-magnetic back-switching capabilities of the write and erase magnetic
domain pattern using double-pump pulse excitations in an iron garnet film with
pure cubic magnetocrystalline symmetry. It is essential to note that forward
and backward magnetization switching is achievable in two distinctive
scenarios: using identical linearly polarized laser pulses and with pulses
having orthogonal polarization planes. By observing the switch of magnetization
at domains independent of the initial state, one can nonthermally toggle the
magnetization, equivalent to XOR logical operation, at frequencies reaching up
to 50 GHz
Nonlinear sub-switching regime of magnetization dynamics in photo-magnetic garnets
We analyze, both experimentally and numerically, the nonlinear regime of the
photo-induced coherent magnetization dynamics in cobalt-doped yttrium iron
garnet films. Photo-magnetic excitation with femtosecond laser pulses reveals a
strongly nonlinear response of the spin subsystem with a significant increase
of the effective Gilbert damping. By varying both laser fluence and the
external magnetic field, we show that this nonlinearity originates in the
anharmonicity of the magnetic energy landscape. We numerically map the
parameter workspace for the nonlinear photo-induced spin dynamics below the
photo-magnetic switching threshold. Corroborated by numerical simulations of
the Landau-Lifshitz-Gilbert equation, our results highlight the key role of the
cubic symmetry of the magnetic subsystem in reaching the nonlinear spin
precession regime. These findings expand the fundamental understanding of
laser-induced nonlinear spin dynamics as well as facilitate the development of
applied photo-magnetism
Phonon-induced magnetization dynamics in Co-doped iron garnets
The developing field of strain-induced magnetization dynamics offers a
promising path toward efficiently controlling spins and phase transitions.
Understanding the underlying mechanisms is crucial in finding the optimal
parameters supporting the phononic switching of magnetization. Here, we present
an experimental and numerical study of time-resolved magnetization dynamics
driven by the resonant excitation of an optical phonon mode in iron garnets.
Upon pumping the latter with an infrared pulse obtained from a free-electron
laser, we observe spatially-varying magnetization precession, with its phase
depending on the direction of an external magnetic field. Our micromagnetic
simulations effectively describe the magnetization precession and switching in
terms of laser-induced changes in the crystal's magneto-elastic energy
Photoinduced magnetic linear dichroism in a YIG:Co film
The spectra of linear dichroism induced by magnetic field are observed in a cobalt-doped yttrium iron garnet (YIG:Co) film grown in the (001) plane. The linear dichroism spectra are highly sensitive to the orientation of the magnetic field. The spectrum measured with the magnetic field directed along the crystallographic axis [100] turned out to have a form identical to the spectrum of the "rigid" photoinduced linear dichroism, known from earlier experiments. The similarity of these spectra may be regarded a sevidence of the magnetic origin of the major part of the optical anisotropy induced by light with polarization E | | [100] in the nonmagnetized YIG:Co film
Magnetic properties of ultrathin Co(0001) films on vicinal Si(111) substrate
In the present work we report on magnetization reversal process, anisotropy and domain structures in ultrathin Au/Co(0001)/Au films deposited on vicinal Si(111) substrates. The measurements were performed using a magneto-optical Kerr effect based magnetometer, a polarizing optical microscope and a ferromagnetic resonance spectrometer. Co thickness induced spin-reorientation from out-of-plane into in-plane magnetization was studied. Changes of in-plane magnetic anisotropy symmetry were deduced from shapes of magneto-optical hysteresis loops and from analysis of angular dependences of the resonance field. The experimental data have been discussed taking into account both uniaxial out-of-plane anisotropy and step-induced uniaxial in-plane anisotropy. A preferential orientation of domain walls in 3ML thick Co films was observed. The finding is explained by the step-induced magnetic anisotropy
Ultrafast nonthermal photo-magnetic recording in a transparent medium
Contains fulltext :
169089.pdf (preprint version ) (Open Access)
Contains fulltext :
169089.pdf (Publisher’s version ) (Open Access
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