An Erratum to this paper has been published: https://doi.org/10.1134/S0031918X24120020

The linear electro-optic effect is investigated in films of RFeO3 compounds (R = Y, Lu, Yb) possessing hexagonal symmetry. A general equation for the optical indicatrix of the film at arbitrary orientation of an external electric field is derived. The equation of the indicatrix in the principal axes, as well as the principal refractive indices, are determined for the particular case of an external electric field orientation along the [010] axis. Two novel optical axes are identified in the presence of an electric field. It was determined that two isonormal modes propagate in the film when light propagates along the [100] direction. The refractive indices associated with these modes were also found. The phase shift associated with the propagation of these modes and caused by the presence of an electric field is calculated. The shift is linear along the electric field, thereby demonstrating the Pockels effect.

Magneto-optical gyrotropic Faraday and Kerr effects are studied in the BiY2Fe5O12 films with thicknesses ranging from 16 to 55 nm, in the wavelength range of 295 nm < lambda < 830 nm (4.2-1.5 eV), and under magnetic fields of up to 1.2 T. It is shown that films produced by ac magnetron sputtering on the single-crystalline diamagnetic yttrium aluminum garnet substrates Y3Al5O12 (001) exhibit high structural and magneto-optical quality. The Verdet constant for diamagnetic Y3Al5O12 is determined, and the magnitude of the Kerr effect is estimated for the polished substrate. It is shown experimentally that for a substrate with diffusely reflective backside, the Kerr effect is about zero, except in the high-energy region. For all BiY2Fe5O12 films investigated, in the saturating magnetic fields of approximately 0.16-0.2 T, the value of specific Faraday rotation reaches 20 deg/mu m (200 000 deg/cm), while the value of the Kerr effect reaches approximately 20 min (5.8 mrad). The critical thickness of the film-substrate interface was estimated, highlighting variations in the Kerr effect spectra associated with a decrease in the Bi content in thin films with the thicknesses of below 27 nm.

X-ray diffraction and electron microscopy were used to examine the crystal structure features of ultrathin (3–50 nm) yttrium orthoferrite films, obtained by magnetron sputtering of stoichiometric composition target on α-Al2O3 substrates with orientation. The morphology and crystal structure of the films differ significantly depending on their thickness. In the thinnest films, several phases are formed, including yttrium orthoferrite with an orthorhombic crystal lattice (o-YFeO3), yttrium hexaferrite with a hexagonal crystal lattice (h-YFeO3), iron-yttrium garnet (Y3Fe5O12), and iron oxides such as hematite and maghemite. The study examines the local composition and determines the orientation ratios between the crystallized phases and the substrate. The films with a thickness greater than 10 nm predominantly exhibit a highly textured phase of o-YFeO3 with a small admixture of iron-yttrium garnet.

Annotation: Magnetooptical Faraday and Kerr effects are studied in the nanosized BiY2Fe5O12 films within the spectral region of 1.3 eV<E<4.5 eV and magnetic fields of up to 10 kOe. It is shown that the thin-films BiY2Fe5O12 with the thicknesses ranging from 5 to 51 nm obtained by magnetron sputtering on the single-crystalline Gd3Ga5O12 substrates have high magneto-optical quality. The specific Faraday rotation for the nanosized Bi0.5Y1.5Fe5O12-delta films reaches about 140000 deg/cm close to that for bulk BiY2Fe5O12. Meanwhile, the polar Kerr effect reaches about 30 min within the range of 1.6 eV-4.1 eV at the magnetic fields above 2 kOe. It is shown that the strong paramagnetic contribution of Gd3Ga5O12 substrates significantly affects the Faraday and Kerr effect for the films. The defining of magnetooptical parameters and Verdet constant for the Gd3Ga5O12 substrate permitted to separate the substrate contribution and reveal peculiarities of spectral dependences of both Faraday and Kerr effects for magnetic films of various thicknesses. The estimated critical thickness of the film-substrate interface region is as large as 35 lattice constants of BiY2Fe5O12. It is shown that the magnetooptical effects for the thin films with the thickness above the critical one correspond to those for bulk BiY2Fe5O12. For samples with the smallest thicknesses of the film (5 nm) the contributions from magnetically dead and magnetically passive layers lead to a drastic reduction in the observable Faraday and Kerr effects with a dominating contribution from the substrate. The high density of displacement dislocations at the film-substrate interface leads to the decrease the magnetooptical quality of the nanosized films.

The magnetic properties of ultrathin single-crystal Y 57 FeO 3 orthoferrite films have been studied by Mössbauer reflectometry. Mössbauer spectra were measured using the ESRF synchrotron in the reflection geometry. As the temperature changes from 3.6 to about 773 K, the splitting of the Zeeman sextet in the spectra successively decreases and, simultaneously, a quadrupole doublet appears in them, which indicates the development of a magnetic phase transition. From the temperature dependences of the magnetic hyperfine field B hf for the main orthorhombic Y 57 FeO 3 phase, Néel temperatures equal to T N ≈ 593, 562, and 567 K and the critical parameter values equal to β ≈ (0.28–0.3) ± 0.02 are determined in films with thicknesses of 28, 6.5, and 4 nm, respectively. An analysis of changing ratio of the line intensities in the Zeeman sextet with temperature makes it possible to trace the successive rotation of the direction of the antiferromagnetic axes in Y 57 FeO 3 toward the surface plane with an increase in the temperature and a decrease in the film thickness.

Optical and magneto-optical properties of the La0.65Ba0.35MnO3 /SrTiO3(0 0 1) thin film with CMR and the paramagnetic-to-ferromagnetic transition at T = 310 K have been investigated in the infrared spectral range. It is shown that magnetotransmission and magnetoreflection of unpolarized light in the film reach up to 10 % at the magnetic field of 4 kOe. The possible physical mechanisms responsible for negative magnetotransmission and positive magnetoreflection in the mid-infrared range are interpreted in the framework of the theory of magne-torefractive effect in manganites. High optical response of the La0.65Ba0.35MnO3 film to an external magnetic field (up to -25 %/kOe in the magnetoreflection) could be used in the design of optical magnetic field sensor, switches and modulators.

The electrical, optical, and magneto-optical properties of La0.69Ba0.31MnO3 – δ thin films with a Curie temperature near room temperature are studied. It is shown that in the region of the phase transition there is a sharp change in the behavior of the temperature dependences of the electrical resistance and optical transparency of the films, which is associated with the insulator-metal transition. In a narrow temperature region near the transition, a change in the external magnetic field leads to the appearance of negative magnetoresistance and magnetotransmission of unpolarized light in the spectral range from 1 to 12 μm. It is shown that the effect of magnetic transmission (magnetoabsorption) in films is mainly due to the contribution of free charge carriers. The magnetic transmission spectra are sensitive to the magnetic and electronic inhomogeneities of the films.

The electrical, optical, and magneto-optical properties of La 0.69 Ba 0.31 MnO 3-delta thin films with a Curie temperature near room temperature are studied. It is shown that in the region of the phase transition there is a sharp change in the behavior of the temperature dependences of the electrical resistance and optical transparency of the films, which is associated with the insulator-metal transition. In a narrow temperature region near the transition, a change in the external magnetic field leads to the appearance of negative magnetoresistance and magnetotransmission of unpolarized light in the spectral range from 1 to 12 μm. It is shown that the effect of magnetic transmission (magnetoabsorption) in films is mainly due to the contribution of free charge carriers. The magnetic transmission spectra are sensitive to the magnetic and electronic inhomogeneities of the films. Keywords: Thin films, manganites, magnetoabsorption, colossal magnetoresistance, IR spectroscopy, metal-insulator transition, magnetic inhomogeneities.

The LiNiPO 4 , LiNi 0.9 Mn 0.1 PO 4 , and LiNi 0.9 Co 0.1 PO 4 single crystals are studied with heat capacity and neutron diffraction measurements over the temperature interval (10–30) K. Two peaks are observed on the temperature dependence of heat capacity for LiNiPO 4 , and LiNi 0.9 Co 0.1 PO 4 samples. One peak indicates the first order phase transition from an antiferromagnetic commensurate (C) structure to an incommensurate (IC) one upon heating. According to neutron diffraction, in LiNiPO 4 the IC ordering is described by the propagation vector k = 2 π / b (0, 0.080, 0) at the Néel temperature T N = 20.8 K, and k = 2 π / b (0, 0.098, 0) at T N = 20.2(1) K for LiNi 0.9 Co 0.1 PO 4 . A further increase in temperature leads to the second order phase transition to a paramagnetic state at critical temperature T IC = 21.7 K and 21.1 K for LiNiPO 4 and LiNi 0.9 Co 0.1 PO 4 , respectively. The C and IC phases coexist over the temperature interval (20.6–20.8) K and (20.2–21.2) K in LiNiPO 4 and LiNi 0.9 Co 0.1 PO 4 , respectively. In the LiNi 0.9 Mn 0.1 PO 4 the magnetic phase transition occurs at T N = 22.7 K, but a magnetic scattering is observed up to 24.6 K.

Features of the magnetic state of antiferromagnetic YFeO3 films thermally treated in an oxygen atmosphere and air have been studied by nuclear magnetic resonance spectroscopy. A strongly inhomogeneous distribution of local magnetic fields with characteristic scales about the interatomic distance has been revealed. The existence of two magnetically nonequivalent positions of iron ions corresponding to its different valence states has been detected in the YFeO3 films under study. The relation between these nonequivalent positions of iron, as well as the degree of distortion of the crystal lattice, depends on the thermal treatment atmosphere.

The paper studies the influence of the composition of a thin-film composite magnetostrictive ferromagnet on the magnetoelectric effect (ME) in ferromagnet/piezoelectric/ferromagnet laminated trilayers at resonant frequencies. The PZT material was used in the piezoelectric layer. The graded composite magnetostrictive ferromagnet with a thickness gradient of the magnetostriction coefficient was obtained by pulsed laser deposition of thin Fe0.72Ga0.28 or Fe0.62Co0.19Ga0.19 films on the surface of Metglas-type 440A amorphous ribbons. The ME was investigated at resonant frequencies of 3 and 9.32 kHz. It is shown that the maximum ME value increases with frequency. The deposition of magnetostrictive thin films decreases the maximum ME value, but increases the Q-factor. The results can be useful for developing sensors of static and low-frequency magnetic fields for magnetic nondestructive testing applications under resonant excitation conditions.

A correlation between the effect of magnetoreflection of natural light and tunnel magnetoresistance has been found in La2/3Ba1/3MnO3 films with a variant structure grown on ZrO2(Y2O3) substrates. It is shown that the magnetoreflection effect and giant magnetoresistance in these films are maximum in the region of magnetic ordering near room temperature (TC ≈ 295 K). Magnetoreflection spectra of a La2/3Ba1/3MnO3 film with a variant structure are formed via the same mechanisms as for films without a variant structure and can be described within the theory of the magnetorefractive effect. The field and temperature dependences of the magnetoreflection exhibit the presence of an additional low-temperature contribution to the reflection of a La2/3Ba1/3MnO3 film due to the tunneling of spin-polarized electrons through structural domain boundaries.

A correlation between the effect of magnetoreflection of natural light and tunnel magnetoresistance has been found in La 2/3 Ba 1/3 MnO 3 films with a variant structure grown on ZrO 2 (Y 2 O 3 ) substrates. It is shown that the magnetoreflection effect and giant magnetoresistance in these films are maximum in the region of magnetic ordering near room temperature ( T C ≈ 295 K). Magnetoreflection spectra of a La 2/3 Ba 1/3 MnO 3 film with a variant structure are formed via the same mechanisms as for films without a variant structure and can be described within the theory of the magnetorefractive effect. The field and temperature dependences of the magnetoreflection exhibit the presence of an additional low-temperature contribution to the reflection of a La 2/3 Ba 1/3 MnO 3 film due to the tunneling of spin-polarized electrons through structural domain boundaries.

A correlation was found between the magnetoreflection of natural light and tunneling magnetoresistance in La2 / 3Ba1 / 3MnO3 films with a variant structure grown on ZrO2 (Y2O3) substrates. It was shown that the magnetoreflection as well as the colossal magnetoresistance, is maximum in the region of magnetic ordering near room temperature (Tc ~ 295 K) of the films. The magnetoreflection spectra of a La2 / 3Ba1 / 3MnO3 film with the variant structure are formed by the same mechanisms as in the case of films without the variant structure and can be described in terms of the theory of the magnetorefractive effect. The field and temperature dependences of magnetoreflection demonstrate the presence of an additional low-temperature contribution to the reflection of the La2 / 3Ba1 / 3MnO3 film due to tunneling of spin-polarized electrons through the boundaries of structural domains.

The paper experimentally demonstrates the possibility of recording low-frequency (20 Hz to 10 kHz) magnetic fields in laminated structures of the composite magnetostrictive thin-film ferromagnet / piezoelectric / magnetostrictive ferromagnet type.Quartz single crystals are used as the piezoelectric material.The composite thin-film-based magnetostrictive ferromagnet is obtained by pulsed laser deposition of magnetostrictive Fe 0.72 Ga 0.28 or Fe 0.62 Co 0.19 Ga 0.19 thin-film layers on the surface of Metglas-type amorphous ribbons.The possibility of detecting both dc and ac magnetic fields in the frequency range from 20 Hz to 10 kHz by measuring the magnetoelectric voltage coefficient (MEVC) in laminated structures is demonstrated experimentally.The influence of the composition of the thin film layer on magnetic noise in the frequency range of 0.5 to 14 Hz is studied.It is shown that the deposition of thin films improves neither the maximum value of MEVC nor the coefficient of linearity at "high" (20 to 50 Oe) magnetic fields in the whole frequency range under study.However, the deposition of Fe 0.62 Co 0.19 Ga 0.19 films enables us to achieve higher coefficients of linearity in the region of zero magnetic fields.Besides, the deposition of thin films increases magnetic noise.The obtained results can be useful in the development of sensors of both dc and ac magnetic fields for nondestructive systems and devices operated at elevated temperatures.

The determination of trends in the emergence of magnetooptical properties and the influence of magnetic phase transitions on the optical properties of magnetic materials is a topical issue in various areas of physics and engineering. The present review is focused on the high-magnitude magnetooptical effects of magnetotransmission and magnetoreflection of unpolarized radiation in a wide spectral region discovered in manganites with colossal magnetoresistance (CMR). The physical mechanisms of these magnetooptical effects in manganites and the potential for their practical application are discussed. The questions requiring further study are formulated.