Electromagnetooptical Effects in Ferri-And Antiferromagnets (original) (raw)
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Magnetoelectric studies of antiferromagnetic crystals in strong magnetic fields
Physica B: Condensed Matter, 1995
Experimental studies of the magnetoelectric effect in the antiferromagnetic crystals Cr20 3, Gd2CuO4 and Sm2CuO 4 have been performed in strong magnetic fields up to 20 T. The magnetoelectric effect is fully determined by the symmetry of the magnetically ordered material and yields hence valuable information about magnetic ground states. When the magnetic symmetry is changed at a magnetic field induced phase transition the magnetoelectric effect exhibits anomalies at the phase transition owing to the fact that the magnetoelectric signal is related to the antiferromagnetic order parameter L. Even at temperatures close to the Nrel temperature TN the obtained experimental data resolve the magnetic properties very well, giving the possibility to study magnetic phase transitions in the critical temperature range.
Crystal chirality magneto-optical effects in collinear antiferromagnets
Physical Review B, 2021
The spin chirality, created by magnetic atoms, has been comprehensively understood to generate and control the magneto-optical effects. In comparison, the role of the crystal chirality that relates to nonmagnetic atoms has received much less attention. Here, we theoretically discover the crystal chirality magneto-optical (CCMO) effects, which depend on the chirality of crystal structures that originates from the rearrangement of nonmagnetic atoms. We show that the CCMO effects exist in many collinear antiferromagnets, such as RuO2 and CoNb3S6, which has a local and global crystal chirality, respectively. The key character of the CCMO effects is the sign change if the crystal chirality reverses. The magnitudes of the CCMO spectra can be effectively manipulated by reorienting the Néel vector with the help of an external electric field, and the spectral integrals are found to be proportional to magnetocrystalline anisotropy energy.
2020
The magneto-optical (MO) effects not only are a powerful probe of magnetism and electronic structure of magnetic solids but also have valuable applications in high-density data-storage technology. Yttrium iron garnet (Y$_3$Fe$_5$O$_{12}$) (YIG) and bismuth iron garnet (Bi$_3$Fe$_5$O$_{12}$) (BIG) are two widely used magnetic semiconductors with strong magneto-optical effects and have also attracted the attention for fundamental physics studies. In particular, YIG has been routinely used as a spin current injector. In this paper, we present a thorough theoretical investigation on magnetism, electronic, optical and MO properties of YIG and BIG, based on the density functional theory with the generalized gradient approximation plus onsite Coulomb repulsion. We find that both semiconductors exhibit large MO effects with their Kerr and Faraday rotation angles being comparable to that of best-known MO materials such as MnBi. Especially, the MO Kerr rotation angle for bulk BIG reaches -1.2...
Magnetic circular dichroism in antiferromagnetic cobalt fluoride
Results are presented of an experimental investigation of magnetic circular dichroism (MCD) of antiferromagnetic cobalt fluoride, for different orientations of the magnetic field: HI( [001 1, HI1 [ 1101, and H(I [ 1 lh]. MCD that is even in the magnetic field intensity was observed, and it is shown that its sign depends on the antiferromagnetic state of the sample. It is shown that the spectra of the MCD linear and quadratic in the magnetic field strength, obtained in Faraday and Voigt experimental geometries, carry independent information on the electronic transitions. In both geometries, the MCD is due mainly to lifting of the sublattice degeneracy of the energy levels of the cobalt ions. The observed singularities of the dispersion dependence of the MCD in the region of the exciton-magnon band, with maximum absorption at the frequency 22769 cm-', are discussed.
Surface nonlinear magneto-optical effects in rhombic antiferromagnetics
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Based on the group theoretical analysis of the nonlinear surface electric susceptibility we propose a new magnetooptical effect that can be used to detect antiferromagnetism at surface and in thin films. With the use of irreducible representation technique for the crystal space groups the formulas for surface polarization on the second-harmonic induced by the incident electromagnetic wave were derived. The principle possibility of antiferromagnetic domain visualization in zero external magnetic field was shown. r 0304-8853/03/$ -see front matter r 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 -8 8 5 3 ( 0 2 ) 0 1 0 8 2 -X
Magnetoelectric and piezomagnetic effects of exchange nature in antiferromagnets
Journal of Magnetism and Magnetic Materials, 1991
As a rule, magnetoelectric and piezomagnetic effects in antiferromagnets have a relativistic origin, i.e. are connected with the relativistic part of spin-lattice and spin-spin interactions. However, in some antiferromagnetic crystals the said effects are of an exchange (Coulomb) nature. Such situations may be revealed and analyzed in the frames of symmetry approach. These systems are interesting due to the fact that, as a rule, exchange interactions are stronger than relativistic ones by two or three orders, therefore, in this case magnetoelectric or piezomagnetic properties manifested themselves more vividly.
Physical Review Materials
We report the synthesis, structure, and magnetism-induced multiferroic properties of the polar magnets RFeWO 6 (R = Tm, Sm, Gd, and Er). All these compounds crystallize in the orthorhombic structure with the polar symmetry Pna2 1 , which results from the ordering of Fe 3+ and W 6+ ions at different crystallographic sites. DC magnetization and specific heat measurements confirm the antiferromagnetic order of Fe 3+ spins at T N1 = 14−18 K and magnetic ordering of R ions at low temperatures. The magnetic order of Fe 3+ ions in these compounds is accompanied by a dielectric anomaly and a change in electric polarization. Intriguingly, a second ferroelectric transition occurs at the magnetic ordering temperature (T N2 = 5.5 K) of Tm 3+ ions in TmFeWO 6. The magnetic field dependent behavior of electric polarization varies with R ion, indicating the coupling between 4 f −3d spins. The emergence of change in ferroelectric polarization at the magnetic ordering temperatures demonstrates the multiferroic nature of the polar magnets RFeWO 6 (R = Tm, Sm, Gd, and Er). Our study indicates that the aeschynite type family of compounds with polar symmetry can be an excellent platform to understand the role of 4 f −3d coupling on multiferroicity.
Physical Review B, 2008
We derive the functional dependence of the specific Faraday rotation ⌰, optical absorption ␣, and magnetooptical figure of merit F ϵ͉⌰͉ / ␣ on the dielectric tensor elements of a uniaxial, magneto-optically active material in a wavelength regime of relative transparency. In addition, we calculate F as a function of Ͻ 2.2 eV for the diamagnetic transition of the octahedrally coordinated Fe 3+ in bismuth doped yttrium iron garnet ͑ 0 = 3.15 eV͒ and show that F achieves a local maximum value in this frequency regime at = 1.25 eV. We also discuss the implications of this result in rare-earth iron garnets for bulk magneto-optical isolators and in orthoferrites for thin film devices. Finally, we discuss the importance of controlling linear birefringence in thin film isolators and its impact on the usefulness of F.