On the magneto-optics of orthoferrites with spin reorientation

The results of magneto-optical investigations into the Γ₂–Γ₄ spin reorientation in an Sm_0.6Tb_0.2Tm_0.2FeO₃ orthoferrite single crystal are reported. The magneto-optical parameters are determined taking into account the dichroism. The orientation of the antiferromagnetic vector in the canted phase is investigated as a function of the magnetic field and temperature. The magnetic anisotropy field strengths are determined by the processing of the results. The orientation contribution to the birefringence is estimated.     

X-ray magneto-optics in lanthanides

Magneto-optical methods in the visible light regime generally lack element specificity, which has become a considerable shortcoming in research on advanced heteromagnetic systems. Using circularly polarized soft x rays tuned to a 4d-4f core-level transition of a lanthanide element, the specularly reflected x-ray intensity changes proportionally to the magnetization of this element and, e.g., hystereses are easily measured element specifically. In contrast to the case of visible light, temperature dependent 4d-4f magneto-optical signals are not influenced by the thermal lattice expansion.     

Null ellipticity in magneto-optics

We determine the relationship between the photon, cyclotron, collision and plasma frequencies which ensures a null ellipticity for electromagnetic wave propagation in a free-carrier magnetoplasma. A comparison is made with the condition for null Faraday rotation.     

Quantum vacuum magneto-optics

In this article we report on the recent experimental activities concerning the magneto-optics of quantum vacuum performed by our team based at the LNCMI of Toulouse. In particular, we will deal with quantum vacuum Cotton–Mouton and inverse Cotton–Mouton effects which have been predicted in the framework of Quantum electrodynamics. Finally, we will present our experiment on photon oscillations into massive particles in the presence of a magnetic field, an effect that could be a signature of physics beyond the standard model.     

On gyrotropic chiral sculptured thin films for magneto-optics

The planewave response of a chiral sculptured thin film with gyrotropic properties is examined, under the assumption of axial excitation. Although the reflectances and the transmittances are definitely affected by gyrotropy, the circular Bragg phenomenon is still exhibited. Most importantly, structural chirality and gyrotropy contribute cooperatively to transmission optical rotation.     

Femtosecond spectrotemporal magneto-optics

A new method to measure and analyze the time and spectrally resolved polarimetric response of magnetic materials is presented. It allows us to study the ultrafast magnetization dynamics of a CoPt3 ferromagnetic film. The analysis of the pump-induced rotation and ellipticity detected by a broad spectrum probe beam shows that magneto-optical signals predominantly reflect the spin dynamics in ferromagnets.     

Spatial dispersion phenomena in magneto-optics

An experimental study of nonreciprocal spatial-dispersion effects in para-(Cd_1−x Mn_xTe), ferro-(LiFe₅O₈), and antiferromagnetic (Cr₂O₃) crystals caused by an external magnetic field or magnetic order is reported. Fiz. Tverd. Tela (St. Petersburg) 40, 946–948 (May 1998)     

On singularities in non-Abelian black holes

Singularities in spherically symmetric black holes in the Einstein-Yang-Mills and the Einstein-Yang-Mills with dilaton theories for the SU(2) group are investigated. Analytical formulas describing the exponentially oscillating and power-law behavior of the metric near a space-like singularity in a solution of the general form are presented. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 12, 855–860 (25 June 1997)     

Interband magneto-optics in single-walled carbon nanotubes

We have carried out magneto-absorption and magneto-photoluminescence experiments on micelle-suspended single-walled carbon nanotubes in magnetic fields up to 45 T. Chirality-assigned spectral peaks exhibit significant changes with increasing magnetic field, which can be quantitatively explained in terms of the theoretically predicted splittings and redshifts of the band edge due to the Aharonov–Bohm effect combined with the magnetic-field-induced alignment of the nanotubes.     

Reflection matrix in magneto-optics of multilayer structures

An expression is given for the reflection matrix of a magnetic multilayer, each layer of which is assumed to be uniformly magnetized in an arbitrary direction. The layer permittivity tensor takes into account optical anisotropy along the direction orthogonal to boundaries and is considered in the linear approximation with respect to two magneto-optical parameters. The result obtained makes it possible to study a large number of various configurations of multilayers and magneto-optical effects in them taking into account the effect of optical anisotropy.     

On Borel singularities in quantum field theory

We consider the effective one-loop lagrangian in a constant electric field. It is shown that perturbation theory behaves as n!, giving rise to singularities in the Borel plane. Comparing with the exact result we show how to integrate these singularities. We suggest that renormalons in QED and QCD should be integrated in a similar way. We make a speculation on a possible interpretation of this integration.     

On the observability of the fieldB (3): Relativistic effects in magneto-optics

It is shown that the novel vacuum fieldB ⁽³⁾ is an experimental observable, and several methods of observation are suggested: these include the pulsed microwave magnetization of a plasma, the optical Aharonov-Bohm effect, and the microwave frequency optical Faraday effect. The effect ofB ⁽³⁾ is presented in the form of relativistically corrected semi-classical theory.     

On the genericity of spacetime singularities

We consider here the genericity aspects of spacetime singularities that occur in cosmology and in gravitational collapse. The singularity theorems (that predict the occurrence of singularities in general relativity) allow the singularities of gravitational collapse to be either visible to external observers or covered by an event horizon of gravity. It is shown that the visible singularities that develop as final states of spherical collapse are generic. Some consequences of this fact are discussed.      

On the concept of spectral singularities

In this paper, we discuss the concept of spectral singularities for non-Hermitian Hamiltonians. We exihibit spectral singularities of some well-known concrete Hamiltonians with complex-valued coefficients.     

Quantum magneto-optics of the graphite family

The optical conductivity of graphene, bilayer graphene, and graphite in quantizing magnetic fields is studied. Both dynamical conductivities, longitudinal and Hall’s, are evaluated analytically. The conductivity peaks are explained in terms of electron transitions. Correspondences between the transition frequencies and the magneto-optical features are established using the theoretical results. We show that trigonal warping can be considered within the perturbation theory for strong magnetic fields larger than 1 T. The semiclassical approach is applied for weak fields when the Fermi energy is much larger than the cyclotron frequency. The main optical transitions obey the selection rule with Δn = 1 for the Landau number n, but the Δn = 2 transitions due to the trigonal warping are also possible. The Faraday/Kerr rotation and light transmission/reflection in quantizing magnetic fields are calculated. Parameters of the Slonczewski-Weiss-McClure model are used in the fit taking the previous de Haas-van Alphen measurements into account and correcting some of them in the case of strong magnetic fields.