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An ellipsometric configuration for measurement of the complex transverse magneto-optical Kerr effect is described that uses a photoelastic modulator (PEM). The real and imaginary parts of the complex transverse Kerr effect are represented as small perturbations of ellipsometric angles psi and Delta. The measurement, based on null ellipsometry and zone averaging, gives high signal typical for modulation techniques and insensitivity to other magnetisation components and system imperfections. The method is demonstrated by the measurement of transverse component during magnetisation reversal in a thin cobalt film. Web of Science 1 art. no. 06017

Experimental study of domain-wall deformation in Co-doped YIG epitaxial films under irradiation by linearly polarized light is reported. A simple theoretical model offering explanation for the observed effects as due to the onset of photo-induced anisotropy in the illuminated volume of the film is proposed. The experimental results are described quantitatively within the model.

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.

We report a method of imaging of the magnetization reversal process using analysis of real-time images of magnetic domain structures in cylindrically shaped microwires. This method uses wide-field polarizing optical microscopy and is based on the magneto-optical Kerr effect (MOKE). The aperture diaphragm in MOKE microscope was used to control the incident angles of the light rays that reached the non-planar surface of the microwire and also determined the MOKE geometries. The movement of the non-central position of the hole in this diaphragm leads to a change in the orientation of the plane of incidence of the light along the perpendicular or the parallel direction to the axial direction of the wire. The visualization of the surface magnetic domain structures is obtained using polar and longitudinal MOKE geometries. The hysteresis loops were obtained by plotting the averaged image contrast as a function of the external magnetic field. The separation of the all-magnetization components is performed using different MOKE geometries in a microscope. We demonstrate the use of vector magnetometry to analyze the orientation of the magnetization in a cylindrically shaped microwire under the influence of an external magnetic field.

A phase-controlled spin wave was non-thermally generated in bismuth-doped rare-earth iron garnet by linearly polarized light pulses. We controlled the initial phase of the spin wave continuously within a range of 180 deg. by changing the polarization azimuth of the excitation light. The azimuth dependences of the initial phase and amplitude of the spin wave were attributed to a combination of the inverse Cotton-Mouton effect and photoinduced magnetic anisotropy. Temporally and spatially resolved spin wave propagation was observed with a CCD camera, and the waveform was in good agreement with calculations. A nonlinear effect of the spin excitation was observed for excitation fluences higher than 100 mJ/cm^2.

Light-induced uniaxial magnetic anisotropy characterized by amplitude, times of creation ${\ensuremath{\tau}}_{1},$ and a vanishing ${\ensuremath{\tau}}_{2}$ was studied. The investigation was performed on YIG (yttrium iron garnet):Co,Ca,Ge liquid-phase epitaxy films using a very sensitive method---observation of changes of magnetic domain structure with a different in-plane magnetization component induced by linearly polarized light pulses. An argon laser $(\ensuremath{\lambda}=488$ nm) was used. The effective field ${H}_{L}$ was introduced to describe the photoinduced uniaxial magnetic-anisotropy amplitude. These domain changes were studied within the temperature range of 160--300 K. With an increase in temperature an increase in ${\ensuremath{\tau}}_{1},$ a decrease in ${\ensuremath{\tau}}_{2},$ and a drastic decrease in ${H}_{L}$ were found. The appearance of the photoinduced anisotropy is explained by light-induced rearrangement of strongly anisotropic ${\mathrm{Co}}^{2+}$ octahedral ions. A microscopic model was proposed where ion rearrangement is connected with electron excitations into the conducting band. Both thermal and light-induced excitations were discussed. Numerical and analytical solutions of kinetic equations describing the model are discussed. The dynamics of light-induced magnetic anisotropy both uniaxial and cubic is analyzed.

We report on the nucleation of circular domains in the outer shell of magnetic, Co-rich, amorphous microwires over a wide range of magnetic field pulse frequencies and amplitudes. Nucleation in the low barrier regime of different numbers of single domains was detected using the magneto-optical Kerr effect. The amplitude and frequency dependence of the domain nucleation probability is described in the framework of a model which agrees well with the experimental data. We have shown that to efficiently drive magnetic domains in microwires with alternating electric current excitation, precise tuning of the frequency and amplitude of the pulse is necessary.

The magnetic anisotropy of ultrathin Co magnetic films epitaxially deposited on vicinal Si(1 1 1) are investigated using ferromagnetic resonance techniques. The experimental data were discussed, taking into account the following contributions to the total magnetic anisotropy energy: magnetocrystalline anisotropy, step-induced uniaxial in-plane anisotropy and perpendicular uniaxial anisotropy. Magnetic anisotropy constants were fitted from experimental results.

We report on modulation of the spin precession in a Co/garnet bilayer by femtosecond laser excitation using time-resolved magneto-optical tools. Damped oscillations in the Faraday rotation transients representing precessional motion of the magnetization vector are observed in both the 2 nm Co layer and 1.8 μm garnet of the bilayer with distinct frequencies differing by about a factor of two. The excitation efficiency of these precessions strongly depends on the out-of-plane magnetic field. The modulation effect with the coupling in a magnetic bilayer can be useful for non-thermally controlling the magnetization of nanomagnets and ultrafast switching in magnetic nanodevices.

Magnetization reversal induced by a circular magnetic field has been studied using the magneto-optical Kerr effect in magnetic microwires. The visualization of the classical effect of a giant Barkhausen jump is reported in a magnetic microwire. It was directly confirmed that the surface giant Barkhausen jump consists of the nucleation of a single circular domain followed by the long distance quick motion of the solitary circular domain walls.

Vicinal substrates provide unique opportunities to engineer the magnetic anisotropies of magnetic ultrathin films. Here we study Co layers on step-bunched Si111 substrates, with or without a Cu interlayer, taken as model samples. To correlate their interface morphology with the step-induced magnetocrystalline anisotropy and the second-order optical polarization, the magnetization reversal, ferromagnetic resonance, and the interface-induced nonlinear magneto-optical spectroscopic response was investigated. We show that both the magnetic anisotropy of the Co layer and the nonlinear magneto-optical response are strongly modified by the addition of the Cu buffer. Thus, the Cu layer reduces the influence of step bunches on the in-plane anisotropy while simultaneously changing the uniaxial anisotropy constant. This is accompanied by a relative change in the rotational harmonics of the nonlinear optical signals that reflect the changes in the interface structure.

Experimental and theoretical results of the investigation of photoinduced changes of magnetic domain structures (DS) inside the irradiated region of an epitaxial YIG : Co film are given. Domain reconstruction was studied under argon laser light pulses. Velocity of photoinduced magnetic anisotropy (PMA) growth was much faster than PMA decay velocity.

We studied magnetization reversal processes and magnetic anisotropy in ultrathin Au∕Co∕Au films deposited on a bifacial Mo(110)/(540) single crystal. The influence of the Co thickness and miscut angle on the spin reorientation from out-of-plane into in-plane magnetization were investigated by means of the magneto-optical Kerr effect (MOKE). In the case of Co grown on a vicinal Au∕Mo(540) substrate, the perpendicular magnetization component was found throughout the 1–8nm Co thickness range. The canted orientation of magnetization was deduced from vectorial MOKE magnetometry. The out-of-plane switching field, which is 160Oe for the perpendicular magnetization, increases to about 960Oe as observed at 8nm Co thickness on the vicinal part. The experimental data are discussed taking into account both uniaxial out-of-plane and in-plane magnetic anisotropy energy terms. The results indicate the possibility of tuning the perpendicular magnetization component with the use of vicinal substrates, and are important fr...