The infra-red absorption spectrum of terbium iron garnet, (TbIG), has been recorded at liquid helium temperature. The energy level scheme was reduced and simulated within the frame of crystal field (cf) theory. The cf parameters of TbIG are not significantly different from those of terbium aluminum garnet, (TbAlG).

Rare-earth iron garnets (RIG) are well known for their numerous interesting magnetic properties, but few works have been done on their optical behavior, especially at low temperatures. This paper studies the optical properties of TbIG, one of the most anisotropic RIG at low temperatures, showing large magnetic and magneto-optical effects, in relation with its magnetic properties. For this purpose, polarized and unpolarized spectra of oriented single crystal of TbIG have been recorded at low temperatures (77, 4.2, and 2 °K) and in external magnetic fields up to 5 T, applied along the principal axis of a (110) plane. Transitions were observed from the ground level 7F6 to other states of the 7FJ multiplets of Tb3+ ions (between 2000 and 5500 cm−1). From the derived energy-level scheme, a set of crystal-field parameters was derived, within the D2 point symmetry. These parameters as well as the energy levels show no noticeable difference with those of Tb3+ ions in paramagnetic TbAlG. Correlations between polarized absorption spectra and magnetic effects will be discussed.

The following features of Pt-Al2O3 cernet coatings deposited by r.f. cosputtering on metallic substrates are reported in this paper. 1.(1) An appropriate choice of cermet composition and coating thickness results in very good optical selectivity.2.(2) This selectivity is increased if the cermet film has a molybdenum underlayer and an Al2O3 overlayer of adequate thickness. An absorptivity a of 0.92 and an emissivity e of 0.14 (at 300°C) have been obtained.3.(3) These selective absorbers are stable at temperatures of up to 400°C when cermet coatings are deposited on stainless steel substrates and of over 600°C when superalloy substrates are used.

The complex polar Kerr magnetooptic effect and reflectivity of Tb3Fe5O12 ferrimagnetic garnet between 2 and 6 eV and the corresponding dielectric tensor element spectra are reported. The spectra are similar to those of Y3Fe5O12. The main differences observed in Tb3Fe5O12 consist in the increase of the values of both diagonal and off-diagonal tensor elements above 4eV and in the splitting in the off-diagonal element spectra near 5.3eV. It is suggested that the strong transition near 4.4eV present in both Y3Fe5O12 and Tb3Fe5O12 involves the states which are localized mostly at the tetrahedral iron ion. The low energy Kerr ellipticities are consistent with the observed near infrared Faraday rotation.

Field and temperature dependence of the magnetization of some anisotropic garnets at low temperature and under dc fields up to 150 kOe are studied. An anisotropy energy taking into account the RE sites local symmetry (orthorhombic) allows: 1) a good fit with experimental results, 2) the description of the magnetic structure (cone type) evolution with applied field.

Magnetooptical spectra Faraday Rotation (F.R.), Magnetic circular dichroism MCD and magnetoreflection ( ) of Y3Fe5-xScxO12garnets have been investigated in the range 15000-21000 cm-1and at 1150 nm. Both bulk crystals and LPE films were used. At 1150 nm Sc substitution brings a net negative contribution to F.R. Also at 40K F.R. remains negative in the region 15000-21000 cm-1. This is confirmed by measurements. MCD spectra indicate bands with a dominant character from a particular sublattice. Results are compared with Ga substitution. The band near 20800cm-1is shown to be responsible for the negative F.R. observed, the contributions from bands at much higher energies compensate each other.

A jump like magnetic transition is observed at relatively weak field in Tb3Fe5O12 when the magnetic field is applied along the hard axis and no transition is observed with the field applied along the easy axis. We believe that this evolution is related to the ”Umbrella” type magnetic structure known to exist in Tb3Fe5O12 at low temperatures.

A linear modulation of light intensity by second‐order magnetooptical interaction (linear magnetic birefringence (L.M.B.) is reported. Theoretical predictions and experimental curves are given for two cubic crystals: YIG and TbiG and for rhombohedral crystal: α−Fe2O3 (Hematite).

The specific circular φF and linear φCM magnetic birefringences of Tb3 Fe5 O12 single‐crystal are reported as a function of the d.c. field Ha and from liquid helium temperature to room temperature. The sign, amplitude and slope of the Cotton‐Mouton effect are strongly dependent on T, Ha and on the direction of this field with respect to the crystal axis. Well defined maxima of % % the slope ΔφF/ΔHa and ΔφCM/ΔHa, observed near T=45 °K, are discussed both from the paramagnetic evolution of the Tb3+ ions in the anisotropic exchange and crystal fields which induce a noncolinear magnetic structure.

AbstractThe crystal field splitting of the energy levels of Fe3+ ions in octahedral and tetrahedral sites of Y3Fe5O12 have been computed between 10000 and 32000 cm−1. The calculation is performed using, first, the cubic field approximation, then the effect of a trigonal distortion, and finally the spin‐orbit interaction in the two magnetic sites. It is shown that the contributionof thetrigonal distortion to the absorption spectrum can be neglected. Thespin‐orbit coupling does not disturb the value of the calculated level energies but induces a coupling between some multiplets. With the use of the spin‐orbit coupling a very good fit between the computed and theexperimental spectra is obtained leading to an assignment of the observed absorption lines which is slightly different from that obtained without the spin‐orbit coupling effects.

A first observation of modulation of light induced by second-order magnetooptical interactions is reported in ferrimagnetic rare-earth garnets (Y3Fe5O12 and Tb3Fe5O12) and discussed on the basis of the anisotropy of the linear magnetic birefringence.

physica status solidi (a)Volume 17, Issue 1 p. K65-K68 Short Note Optical and magnetooptical properties of epitaxial YIG films R. Krishnan, R. Krishnan Laboratoire de Magnétisme, C.N.R.S., Meudon–BellevueSearch for more papers by this authorH. Le Gall, H. Le Gall Laboratoire de Magnétisme, C.N.R.S., Meudon–BellevueSearch for more papers by this authorTran Khanh Vien, Tran Khanh Vien Laboratoire de Magnétisme, C.N.R.S., Meudon–BellevueSearch for more papers by this author R. Krishnan, R. Krishnan Laboratoire de Magnétisme, C.N.R.S., Meudon–BellevueSearch for more papers by this authorH. Le Gall, H. Le Gall Laboratoire de Magnétisme, C.N.R.S., Meudon–BellevueSearch for more papers by this authorTran Khanh Vien, Tran Khanh Vien Laboratoire de Magnétisme, C.N.R.S., Meudon–BellevueSearch for more papers by this author First published: 16 May 1973 https://doi.org/10.1002/pssa.2210170156Citations: 19AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume17, Issue116 May 1973Pages K65-K68 RelatedInformation

L'analyse en seconde quantification des interactions magneto-optiques dans un cristal ferromagnetique montre que les effets statiques (effets Faraday et Cotton-Mouton) et dynamiques (Raman a 1 et 2 magnons) apparaissent comme des diffusions spin-photon elastiques et inelastiques respectivement. Les relations physiques et analytiques entre ces differents effets dispersifs induits par les transitions dipolaires electriques et magnetiques sont precisees. On montre que les susceptibilites Raman a 1 et 2 magnons sont proportionnelles au carre des birefringences magnetiques specifiques circulaire et lineaire respectivement. Enfin les anomalies importantes de diffusion Raman a 1 magnon que nous avons observees recemment sont interpretees a partir de l'influence des interactions magneto-optiques du second ordre sur les diffusions inelastiques du premier ordre.

AbstractThe second quantization of the magneto‐optical interactions in ferromagnetic crystals is extended to second‐order processes. From the electric and magnetic dipole transitions induced by an incident radiation, the evolution of the electromagnetic field is analysed in the cases of bi‐gyrotropic and quadratic magneto‐optical materials. The physical and analytical relations between the elastic (linear magnetic birefringence) and inelastic (two‐magnon Raman effects) scatterings are derived from the second‐order magneto‐optical Hamiltonians. It is shown that the two‐magnon Raman susceptibility is proportional to the second power of the specific linear magnetic birefringence. In isotropic media the second‐order magneto‐optical interactions may be separated in an isotropic (or scalar) part and in an anisotropic (or tensorial) part. From the corresponding Hamiltonians the polarization rules are deduced for the second‐order inelastic scatterings. In ferrites and orthoferrites the first‐ and second‐order magneto‐optical constants may have equivalent values. As supported by experiments the influence of the quadratic magneto‐optical interactions on the first‐order inelastic scattering is shown from the magneto‐optical polarization and Hamiltonians. The one‐magnon Stokes component may be higher than the anti‐Stokes component when the polarization of the incident photons is parallel to the dc magnetization. The opposite result is obtained with light polarized perpendicular to the dc magnetization. The one‐magnon Raman Hamiltonians and susceptibilities modified by the quadratic effects are derived from the optical polarization and compared with experimental data.