21,789 research outputs found
Analytical expression of the magneto-optical Kerr effect and Brillouin light scattering intensity arising from dynamic magnetization
Time-resolved magneto-optical Kerr effect (MOKE) and Brillouin light
scattering (BLS) spectroscopy are important techniques for the investigation of
magnetization dynamics. Within this article, we calculate analytically the MOKE
and BLS signals from prototypical spin-wave modes in the ferromagnetic layer.
The reliability of the analytical expressions is confirmed by optically exact
numerical calculations. Finally, we discuss the dependence of the MOKE and BLS
signals on the ferromagnetic layer thickness
Oscillatory Spin Polarization and Magneto-Optic Kerr Effect in Fe3O4 Thin Films on GaAs(001)
The spin dependent properties of epitaxial Fe3O4 thin films on GaAs(001) are
studied by the ferromagnetic proximity polarization (FPP) effect and
magneto-optic Kerr effect (MOKE). Both FPP and MOKE show oscillations with
respect to Fe3O4 film thickness, and the oscillations are large enough to
induce repeated sign reversals. We attribute the oscillatory behavior to
spin-polarized quantum well states forming in the Fe3O4 film. Quantum
confinement of the t2g states near the Fermi level provides an explanation for
the similar thickness dependences of the FPP and MOKE oscillations.Comment: to appear in Phys. Rev. Let
Angle Dependence of Photonic Enhancement of Magneto-Optical Kerr Effect in DMS Layers
We investigate theoretically an angle dependence of enhancement of polar
magneto-optical Kerr effect (MOKE) obtained thanks to a deposition of a
paramagnetic Diluted Magnetic Semiconductor (DMS) layer on one-dimensional
photonic crystal layer. Our transfer matrix method based calculations conducted
for TE and TM polarizations of the incident light predict up to an order of
magnitude stronger MOKE for a (Ga,Fe)N DMS layer when implementing the proposed
design. The maximum enhancement for TE and TM polarization occurs for the light
incidence at the normal and at the Brewster angle, respectively. This indicates
a possibility of tuning of the MOKE enhancement by adjustment of the
polarization and the incidence angle of the light.Comment: 6 figure
Thickness dependence of linear and quadratic magneto-optical Kerr effect in ultrathin Fe(001) films
Magneto-optical Kerr effect (MOKE) magnetometry is one of the most widely
employed techniques for the characterization of ferromagnetic thin-film
samples. Some information, such as coercive fields or anisotropy strengths can
be obtained without any knowledge of the optical and magneto-optical (MO)
properties of the material. On the other hand, a quantitative analysis, which
requires a precise knowledge of the material's index of refraction n and the MO
coupling constants K and G is often desirable, for instance for the comparison
of samples, which are different with respect to ferromagnetic layer
thicknesses, substrates, or capping layers. While the values of the parameters
n and the linear MO coupling parameter K reported by different authors usually
vary considerably, the relevant quadratic MO coupling parameters G of Fe are
completely unknown. Here, we report on measurements of the thickness dependence
(0-60nm) of the linear and quadratic MOKE in epitaxial bcc-Fe(001) wedge-type
samples performed at a commonly used laser wavelength of 670nm. By fitting the
thickness dependence we are able to extract a complete set of parameters n, K,
(G11 - G12), and G44 for the quantitative description of the MOKE of
bcc-Fe(001). We find sizable different n, K, and G parameters for films thinner
than about 10nm as compared to thicker films, which is indicative of a
thickness dependence of the electronic properties or of surface contributions
to the MOKE. The effect size of the quadratic MOKE is found to be about a third
of the record values recently reported for Co2FeSi.Comment: 8 pages, 5 figure
Magneto-optic Kerr effect in a spin-polarized zero-moment ferrimagnet
The magneto-optical Kerr effect (MOKE) is often assumed to be proportional to
the magnetisation of a magnetically ordered metallic sample; in metallic
ferrimagnets with chemically distinct sublattices, such as rare-earth
transition-metal alloys, it depends on the difference between the sublattice
contributions. Here we show that in a highly spin polarized, fully compensated
ferrimagnet, where the sublattices are chemically similar, MOKE is observed
even when the net moment is strictly zero. We analyse the spectral ellipsometry
and MOKE of Mn 2 Ru x Ga, and show that this behaviour is due to a highly
spin-polarized conduction band dominated by one of the two manganese
sublattices which creates helicity-dependent reflectivity determined by a broad
Drude tail. Our findings open new prospects for studying spin dynamics in the
infra-red.Comment: 7 pages, 7 figure
Effect of picosecond strain pulses on thin layers of the ferromagnetic semiconductor (Ga,Mn)(As,P)
The effect of picosecond acoustic strain pulses (ps-ASP) on a thin layer of
(Ga,Mn)As co-doped with phosphorus was probed using magneto-optical Kerr effect
(MOKE). A transient MOKE signal followed by low amplitude oscillations was
evidenced, with a strong dependence on applied magnetic field, temperature and
ps-ASP amplitude. Careful interferometric measurement of the layer's thickness
variation induced by the ps-ASP allowed us to model very accurately the
resulting signal, and interpret it as the strain modulated reflectivity
(differing for probe polarizations), independently from dynamic
magnetization effects.Comment: 6 pages, 5 figure
Influence of lateral geometry on magnetoresistance and magnetisation reversal in Ni80Fe20 wires
The magnetisation reversal processes and magnetoresistance behaviour in micron-sized Ni80Fe20 wires with triangular and rectangular modulated width have been studied. The wires were fabricated by electron beam lithography and a lift-off process. A combination of magnetic force microscopy (MFM), magneto-optical Kerr effect (MOKE) and magnetoresistance (MR) measurements shows that the lateral geometry of the wires greatly influences the magnetic and transport properties. The width modulations modify not only the shape-dependent demagnetising fields, but also the current density. The correlation between the lateral geometry, the magnetic and the transport properties is discussed based on MFM, MOKE and MR results
Magnetic microstructure and magnetotransport in Co2FeAl Heusler compound thin films
We correlate simultaneously recorded magnetotransport and spatially resolved
magneto optical Kerr effect (MOKE) data in Co2FeAl Heusler compound thin films
micropatterned into Hall bars. Room temperature MOKE images reveal the
nucleation and propagation of domains in an externally applied magnetic field
and are used to extract a macrospin corresponding to the mean magnetization
direction in the Hall bar. The anisotropic magnetoresistance calculated using
this macrospin is in excellent agreement with magnetoresistance measurements.
This suggests that the magnetotransport in Heusler compounds can be adequately
simulated using simple macrospin models, while the magnetoresistance
contribution due to domain walls is of negligible importance
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