Magneto-optical Contribution Research Articles

Magneto-Optical Functions at the 3p Resonances of Fe, Co, and Ni: Abinitio Description and Experiment.

We present experimental data and a complete theoretical description of the magneto-optical contributions to the complex refractive index in the extreme ultraviolet (XUV) range covering the 3p resonances of Fe, Co, and Ni. The direct comparison of the two allows us to conclude that many-body corrections to the ground state and local field effects are crucial for an accurate description of M-edge spectra. Our results are relevant for investigation of static magnetization, via XUV spectroscopy of multielement systems, as well as the dynamics of magnetization, as needed in the study of femtomagnetism and spintronics.

Magneto-optical Kerr effect in ZnTMO2 (TM=Cr, Mn, Fe, Co and Ni)

First principles generalized gradient full potential density-functional calculations were performed to predict the optical and magneto-optical (MO) properties of the chalcopyrite compounds ZnTMO2, TM=Cr, Mn, Fe, Co and Ni. Detailed investigation of the electronic band structure and density of states is reported. The optical properties in the 0–8eV energy range are analyzed in terms of band structure transitions. As for the magneto–optical properties, our results show that the studied compounds have peaks in the Kerr rotation ranging from infrared to ultraviolet radiation, with ZnFeO2 having the highest Kerr rotation angle of 10° and −8.46° at 0.35eV and 4.59eV, respectively. The peaks in the Kerr spectra were assigned to the optical and magneto–optic contributions. Our calculated function of merit for these compounds indicates that these compounds might be useful for technological application in high density storage.

Light reflection from nonlinear optical dielectric film on a bigyrotropic magnetoelectric substrate at angles close to Brewster angles

Light reflection from the interface of a dielectric film, characterized by a cubic optical nonlinearity, on a bigyrotropic substrate magnetoelectric substrate is investigated theoretically. Relations are obtained for the reflection coefficient as a function of the incidence angle of the light for the main magneto-optic configurations: polar, longitudinal, and transverse. The effect of the magneto-electric and magneto-optical contributions to the electric polarization of such a biaxial structure on the polarization state of the light reflected at angles close to the Brewster angles is studied.

Effective Transition Probability for the Faraday Effect of Lanthanide(III) Ion Solutions

The Faraday effects of 14 lanthanide(III) ion solutions were systematically analyzed on the basis of the Faraday C term. The effective transition probability, K, which measures the magneto-optical contribution of the 4f(n) --> 4f(n-1)5d transition to the molar Verdet constant, was determined. Linear correlations between K and the square root of the molar magnetic susceptibility of the lanthanide(III) ions, chi(m)(1/2), were obtained. From the observed new regularity, K for promethium(III) was estimated.

Localized surface plasmon resonance effects on the magneto-optical activity of continuous Au/Co/Au trilayers

We study how the magneto-optical activity in polar configuration of continuous Au/Co/Au trilayers is affected by the excitation of localized plasmon resonances of an array of Au nanodiscs fabricated on top of them over a dielectric SiO(2) spacer. We show that the effect of the nanodiscs array is twofold. First, it optimizes the absorption of light at specific photon energies corresponding to the localized surface plasmon excitation of the array, modifying the reflectivity of the system (we define this effect as the purely optical contribution). Second, upon localized plasmon resonance excitation, the electromagnetic field in the whole system is redistributed, and an enhanced magneto-optical activity occurs at those energies where the electromagnetic field in the magnetic layer is increased (this effect is identified as the purely magneto-optical contribution of the nanodiscs array).

Magneto-optic properties of electron cyclotron resonance ion beam sputtered and magnetron sputtered Co/Pt multilayers

An investigation of the magneto-optic properties of single Co films sandwiched by Pt films is presented. The films are grown via electron cyclotron resonance ion beam sputtering and magnetron sputtering. Kerr rotation and ellipticity are measured for the multilayers, varying Pt cap, Co, as well as Pt buffer layer thickness. The set of data allows the separation of optic and magneto-optic contributions to the Kerr signals. The magneto-optic constants (Voigt constants) are determined and compared with literature values. The striking result is the strong difference of the magneto-optic constants for ultrathin and thick Co films. The analysis of the data reveals that for ultrathin films, the Kerr signals have contributions that come presumably from the interfaces, indicative of polarized Pt.

Unusual temperature dependence of polar Kerr rotation in ultrathin Co films grown on Pd(1 1 0)

For Co films on Pd(1 1 0) covered with Au, the polar hystersis loops measured at 120 K are reversed below 2.7 ML with respect to those of thicker Co films, which is due to the negative contribution to polar Kerr rotation from the Co/Pd interface dominating in this thickness range over the positive polar Kerr rotation from the non-interface part of the Co film. Near the film thickness where the Kerr rotation changes sign a remarkable combination of two loops (normal and reversed) of two slightly different coercivities is observed regarded as a superposition of two different magneto-optical contributions corresponding to thinner and thicker parts of the Co film. The thin and thick film areas could have different temperature dependence of magnetization (the negative contribution could depend stronger on temperature since it is related to the thinner part of the film), leading to the increasing total polar Kerr rotation with increasing temperature.

Magneto-optical properties of Heusler compounds from a first-principles approach

Accurate first principles calculations were performed to predict the optical and magneto-optical properties of a large set of Heusler compounds. The optical properties are explained in terms of relevant transitions from the underlying band-structure, suggesting that the joint density of states plays a role in shaping the optical spectra. As for the magneto-optical properties, our results show that most of the Heusler compounds have peaks in the Kerr rotations of the order of 0.5°, typical for 3d-based materials. The Kerr spectra are rather similar for all considered Heuslers, consistent with their overall comparable band-structure; the peaks in the Kerr angles were traced back to their optical versus magneto-optical contributions. This careful ab initio analysis is extremely helpful in view of engineering the Kerr rotation for technological purposes.

Topology-dependent interface contribution to magneto-optical response from ultrathin Co films grown on the (001), (110), and (111) surfaces of Pd

We have grown ultrathin epitaxial Co films on three low-index surfaces of Pd. Their magnetic properties studied by the magneto-optical Kerr effect are correlated with the surface morphology analyzed by scanning tunneling microscopy. A perpendicular magnetic anisotropy in the films appeared after exposure to residual gas atmosphere at low temperature, after coverage with an Au overlayer or after annealing at $370\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and above. For one- and two-monolayer-thick films the hysteresis loops are reversed with respect to those of thicker Co films. This is due the negative polar Kerr rotation contribution from the $\mathrm{Co}∕\mathrm{Pd}$ interface dominating over the positive polar Kerr rotation contribution from the noninterface part of the Co film. Reversed loops are not seen when the Co films grow in a three-dimensional mode. This indicates a clear correspondence between the mode of growth and the magneto-optical response. Near the film thickness where the Kerr rotation changes sign a remarkable temperature behavior is observed which is discussed as a superposition of two different magneto-optical contributions. The results qualitatively agree with the available ab initio band-structure calculations for the $\mathrm{Co}∕\mathrm{Pd}$ multilayer structures with variable thickness of the Co layers.

Fast Polarization Effects in Optical Aerial Cables Caused by Lightning and Impulse Current

The effects of lightning and impulse currents on the perturbations of the state of polarization (SOP) of optical beams transmitted on aerial cables are emulated in a laboratory environment. Submicrosecond-resolved measurements enable us to distinguish and quantify the magnetooptic contributions due to the discharge current. The maximum of Faraday-induced circular birefringence associated to natural strokes is estimated in /spl Delta/n/sub lr//spl ap/10/sup -7/ and may lead in a few microseconds to iterate swapping between orthogonal SOPs. The corresponding peak in relative phase delay, cumulated in transmission along a span, is evaluated as /spl Delta//spl tau//sub lr//spl ap/0.3 ps.

Magneto-optical contribution of interfaces in ultrathin film Au/Co/Au structures

Magneto-optical (MO) polar Kerr rotation (PKR) and ellipticity (PKE) spectroscopic studies of Au(5 nm)/Co(0.4–1.8 nm)/Au(25 nm) ultrathin film sandwiches showed that the spectra can be represented as a sum of two components: one (nearly) linearly dependent plus one independent of the Co layer thickness, t Co. The two components were determined from the experiments on well defined sandwiches with stepped wedge Co layers after eliminating the MO contribution from the glass substrate and sandwiching the Au layers. Two effects responsible for the t Co-independent components: (1) spin polarization in the Au monolayers adjacent to Co and (2) roughness at AuCo interfaces were considered. The results of modelling and a comparison with MO spectra of gold suggest that latter effect is dominant.

Magnetooptical properties of YIG:Sc single crystals

Faraday rotation measurements at 1152 nm were performed on single-crystal oriented platelets of ferrimagnetic garnets of formula Y 3Fe 5 − x Sc x O 12 (0 < x < 0.55) as a function of temperature and magnetic field. Sc 3+ ions substituting for octahedral Fe 3+ have a much greater influence on the spontaneous Faraday rotation than found for the corresponding tetrahedral diamagnetic substitution. The Faraday rotation susceptibility is constant and independent of Sc concentration. The results are interpreted as the sum of magneto-optical contributions from the [a] and (d) sublattices proportional to their magnetizations and induced by magnetic and electric dipole transitions. The electric magneto-optical coefficients deduced from a least squares fit of the experimental values are linear functions of the Sc concentration.

Optical and magneto-optical properties of Fe0.28TaS2

Ellipsometry and polar magneto-optical Kerr effect measurements were performed on Fe0.28TaS2 in the photon energy region 0.6-5 eV. The complex dielectric tensor was calculated from the measured data. Strong anisotropy was found in the diagonal elements of the dielectric tensor. Strong absorption bands at 1.6 and 3.8 eV for light polarized perpendicular to the c-axis were attributed to transitions between Ta 5d bands. In the off-diagonal element of the dielectric tensor five transitions with diamagnetic line shapes were observed. These transitions are between Fe 3d and Ta 5d states. The large magneto-optical contribution results from the large exchange splitting of the Fe 3d states combined with the large spin-orbit splitting of Ta 5d states.

Magneto-optical Kerr-effect study of the high-field superconductors Eu1-xPbxMo6S8 and Eu1-xSnxMo6S8-ySey.

A magneto-optical study on high-field superconductors is presented. We have investigated the four Chevrel-phase compounds PbMo{sub 6}S{sub 8}, EuMo{sub 6}S{sub 8}, Eu{sub 0.5}Pb{sub 0.5}Mo{sub 6}S{sub 8}, and Eu{sub 0.75}Sn{sub 0.25}Mo{sub 6}S{sub 7.6}Se{sub 0.4} in fields up to 120 kOe and temperatures down to 0.5 K. From our optical data we conclude that all these compounds are poor metals with rather few free carriers having effective masses of the order of 10{ital m}{sub {ital e}}. Up to 12 eV, the real part {sigma}{sub 1{ital x}{ital x}} of the optical conductivity is dominated by Mo {ital d}{leftrightarrow}S {ital p} transitions. Agreement is found between {sigma}{sub 1{ital x}{ital x}} and the value of {sigma}{sub 1{ital x}{ital x}}{sup theor} that has been derived from a self-consistent band-structure calculation. In the magneto-optical spectra two dominant Eu{sup 2+} 4{ital f}{r arrow}5{ital d} transitions have been found, a 4{ital f}{r arrow}5{ital de}{sub {ital g}} transition at 2.3 eV and a 4{ital f}{r arrow}5{ital t}{sub 2{ital g}} transition at 3.2 eV. A detailed comparison with the europium monochalcogenides yields a 60% smaller radial overlap integral of the Eu{sup 2+} 4{ital f} and 5{ital d} wave functions in the europium Chevrel phases than in the europium monochalcogenides. A strongmore » deviation from a Brillouin function is found in the Kerr rotation at the energy of the Eu{sup 2+} 4{ital f}{r arrow}5{ital d} transitions as a function of magnetic field at temperatures below 5 K. This deviation is due to another transition, which involves spin-polarized Mo {ital d} states and which we assign to Mo {ital d}{r arrow}S {ital p} transitions by consideration of the line shape and the sign of its magneto-optical contribution.« less

Ｎｄ‐（Ｆｅ，Ｃｏ）膜の磁気光学力‐効果

Magneto-optical contribution of Nd in vacuum evaporated Nd-(Fe, Co) films has been investigated by measuring the wavelength dependence (λ=250∼800 nm) of Kerr rotation (θK), together with the spectra of photoelectrons emitted under X-ray (XPS). The Kerr rotation for Nd-Co films increases with decreasing λ when Nd concentration is over 14 at.% and shows a peak at 300 nm, while the Kerr spectra of Nd-Fe films become flat with increasing Nd content. The compositional dependence of Kerr spectra for Nd-Co and Nd-Fe films is characterized by the following two factors, 1) the contribution of Nd to θK at short wavelength, and 2) the differences of the Kerr spectra between crystalline and amorphous states of Co or Fe. The XPS intensity for Nd-Co and Nd-Fe shows a maximum at about 4.2 eV below the Fermi level, which corresponds to the peak of θK at 300 nm. In pseudobinary system Nd-(Fe, Co) films, θK is larger than any other binary system with the same Nd composition in the entire wavelength region, and Nd22(Fe65Co35)78 film shows θK of about 0.58° at 300 nm.