The Fe100-xZrx (with x = 6-13 at%) films are formed on glass-ceramic substrates by ion-beam deposition. The structural and magnetic states of the films were analyzed using X-ray diffraction, M & ouml;ssbauer and magneto-optical (based on transverse Kerr effect) spectroscopy, and magnetometry. All measurements were performed at room temperature for as-deposited films and the films annealed at 300 and 500 degrees & Scy;. Analysis of the whole set of obtained data shows that a mixed (nanocrystalline + amorphous) structure forms in the films. The nanocrystalline phase is the Zr solid solution in alpha-Fe, alpha-Fe(Zr). The as-deposited films with the high Zr content (& khcy; > 8.3 at%) are characterized by dominant amorphous constituent, whereas the films with & khcy; <= 7.1 at.% are nanocrystalline and characterized by a very low content of the amorphous constituent. Since, at room temperature, the alpha-Fe(Zr) phase is ferromagnetic and the amorphous one is paramagnetic, the magnetic properties of the films in the as-deposited and annealed states are determined by relative content of these structural constituents and by Zr content in the alpha-Fe(Zr) phase. This fact explains abrupt changes in the magnetic properties of the as-deposited films when x changes from 7.1 to 8.3 at% and an increase in the magnetization of the films with x > 8.3 at% after the annealing at 500 degrees & Scy; leading to an increase in the nanocrystalline phase content.

In this work, we investigated structural, microstructural, magnetic, magnetooptical and magnetotransport properties of InSb-MnSb composites in the intermediate composition range (36.5-57.1 mol.% of MnSb) with the addition of small amount of Sn. Here we focus on the comparison of results for composite crystals synthesized from the melt at equilibrium conditions and via quenching. We show that quenching conserves phase composition of studied systems, but substantially changes the spatial distribution of binary components, which manifests as the decrease of sizes and distances between MnSb inclusions. The latter is accompanied with the increase of microstrain values for both InSb and MnSb phases. The presence of small amount of Sn component results in the formation of SnSb phase, which, however, have no effect on other phases and can be considered as a part of InSb matrix. Magnetic and magnetooptical properties of studied composites are determined solely by the MnSb phase, while quenching results in magnetic hardening, due to the change in domain structure of ferromagnetic inclusions. Magnetotransport properties of the InSb(SnSb)-MnSb composites contain contributions related both to ferromagnetic inclusions and semiconducting matrix. Observed quenching-related effects also reflects the difference in the spatial distribution of components. Obtained results for quenched InSb(SnSb)-MnSb crystals are qualitatively similar to that of the quenched GaSb-MnSb composite suggesting that reported features of magnetic, magnetooptical and magnetotransport features are universal for AIIISb-MnSb composites obtained in a similar manner.

The magneto-optical transverse Kerr effect (TKE) spectroscopy allows non-contact investigation of nanostructures, giving valuable information about the microstructure of samples. In this paper, within the framework of effective medium approach we analyze the effect of granule size on the magneto-optical spectra of magnetic nanocomposites. We consider the influence of various microscopic parameters such as plasma frequency, relaxation time, the coefficient of the anomalous Hall effect inside the granule and on its surface on the amplitude and profile of the TKE spectrum. Three main mechanisms are considered: the quasi-classical size effect, spin-orbit interaction enhancement at the granule surface and change of the percolation threshold.

An Erratum to this paper has been published: https://doi.org/10.1134/S0031918X2355001X

Composite Films (Сd3As2)100-X(MnAs)X on silicon and sitall substrates with a concentration of Mn 5.8-16.4 at.% were obtained by vacuum-thermal evaporation. The structural properties of the films were investigated by X-ray phase analysis and scanning electron microscopy. Magneto-optical properties were studied by the method of the equatorial Kerr e ect (EEC) in the energy range of 0.5-4.0 eV in magnetic elds with a strength of up to 3 kE at a temperature of 20-300 K. In the geometry of the equatorial Kerr effect, spectral, field and temperature dependences of the EEC are obtained. The analysis of experimental data showed that with a Mn content of more than 12.9 at.% of the films contain the α′′-phase of the topological Dirac semimetal Cd3As2 in the form of large granules, as well as ferromagnetic MNAs granules. The Curie temperature of lms depends on the Mn content in them and is less than the temperature of bulk samples ofMPas. When the Mp content in the lm is 5.8 at.% and 6.4 at.%, the magneto-optical response is not detected, which indicates the formation of a superparamagnetic state or a spin glass state at low concentrations of Mn. With a film content of Mn 9.9 at%. A signi cant change in magneto-optical spectra was detected, which indicates the formation of MNAs nanoclusters and partial dissolution of Mn in the Cd3As2 matrix.

Composite films of (Cd _3 As _2 ) _100-X (MnAs) _X on silicon and sitall substrates with Mn concentration of 5.8–16.4 at % were obtained by vacuum-thermal evaporation. The structural properties of the films were investigated by X-ray phase analysis and scanning electron microscopy. Magneto-optical properties were studied using the transverse Kerr effect (TKE) method in the energy range of 0.5–4.0 eV in magnetic fields up to 3 kOe at temperatures of 20–300 K. In the geometry of the transverse Kerr effect, the spectral, field, and temperature dependences of TKE were obtained. Analysis of experimental data showed that at Mn contents more than 12.9 at % the films contain the α^'' -phase of the topological Dirac semimetal Cd _3 As _2 in the form of large granules, as well as ferromagnetic MnAs granules. The Curie temperature of the films depends on their Mn content and is lower than that of bulk MnAs samples. At Mn contents in the film of 5.8 and 6.4 at % , no magneto-optical response was detected, indicating the formation of a superparamagnetic state or a spin glass state at low Mn concentrations. At an Mn content in the film of 9.9 at % , a significant change in magneto-optical spectra was observed, indicating the formation of MnAs nanoclusters and partial dissolution of Mn in the Cd _3 As _2 matrix.

В диапазоне температур 3-250 К в полях до 14 Тл обнаружена сильно немонотонная температурнаязависимость магнетосопротивления пленочных нанокомпозитов (CoFeB)x(LiNbOy )100-x при содержаниях x ≈ 40-48 ат. % вблизи перколяционного перехода на изолирующей стороне. Магнетосопротивление имеет минимум при 40 K, резко возрастая при понижении температуры. Такое поведение магнетосопротивления объясняется сосуществованием в НК суперферромагнитных областей с обменно-связанными гранулами, отделенных областями из суперпарамагнитных гранул. При этом увеличение отрицательного магнетосопротивления при T > 40 К обусловлено разрушением суперферромагнитного упорядочения, а рост магнетосопротивления при T < 40 K связан с процессами упругого совместного туннелирования через цепочки гранул. В условиях насыщения намагниченности проявляется дополнительный отрицательный вклад, обусловленный, вероятно, эффектами квантовой интерференции. При T < 4 K наблюдается двухъямный характер полевой зависимости магнетосопротивления, связанный с проявлением положительного вклада, конкурирующего с отрицательным магнетосопротивлением.

Magnetooptical spectroscopy is an effective method for studying the magnetic microstructure of homogeneous and heterogeneous magnets. This review is devoted to analysis of numerous factors affecting the intensity and spectral dependence of a magnetooptical signal of the equatorial Kerr effect in nanocomposites “ferromagnetic metal–dielectric” in the visible and near infrared spectral regions. Examples of the influence of the metal concentration, nanoparticle size and shape, the substrate, the material of the dielectric, the amorphization of grains, the deposition method, and other factors on the magnetooptical spectrum are considered. The differences in the magnetooptical spectra for the superparamagnetic, superferromagnetic, and ferromagnetic states are demonstrated. It is noted that in the presence of fractions with different field dependences of the magnetization in a nanocomposite, the magnetooptical signal is not proportional to the total magnetization. Examples of enhancement and sign inversion of the magnetooptical signal in nanocomposites are considered. The possibility of the description of magnetooptical spectra using the methods of the effective medium (the Bruggeman method and the Maxwell–Garnett symmetrized approximation) is discussed.

A strongly nonmonotonic temperature dependence of the magnetoresistance in (CoFeB)x(LiNbOy)100 – x film nanocomposites (x ≈ 40–48 at

Nanocomposites (CoFeB)x(LiNbO3)100 – x with x = 17–48 at % have been synthesized by ion beam sputtering of a composite target comprised of Co40Fe40B20 and LiNbO3 onto silicon substrates, and the tran-sitions from the superparamagnetic state to the superferromagnetic and ferromagnetic states with an increase in the concentration of the magnetic component are studied by magneto-optical methods. The magneto-optical properties have been investigated in the geometry of the equatorial (transverse) Kerr effect (TKE). Magneto-optical spectra are recorded in the range of 0.5–4.0 eV in fields up to 2.5 kOe at 20–300 K, field and temperature dependences of the TKE at certain wavelengths are obtained, and the domain structure during magnetization reversal is visualized using a magneto-optical Kerr microscope. It is shown that the sample with x = 17 at % is superparamagnetic at temperatures above the blocking temperature (about 30 K). The interaction between the granules is considerable already at x = 20 at %, the transition to the superferro-magnetic state occurs at x ≈ 32–36 at %, and the transition to the ferromagnetic state occurs at x ≈ 44 at %near the metal–dielectric transition, i.e., at a concentration below the percolation transport threshold.

In this work, we studied properties of the GaSb-MnSb composite (30 mol.% GaSb + 70 mol.% MnSb), synthesized from a melt of elemental precursors and subjected to the post-growth quenching procedure. We used a combination of experimental methods to specify phase composition of studied systems and elemental composition of each phase. Presented results suggest that studied composites can be considered as an ensemble of large ferromagnetic MnSb inclusions (with sizes of order of 10 mu m) embedded in GaSb matrix with small amount of diluted Mn atoms in it. We show that magnetic and magnetooptical properties of composites are primarily defined by the MnSb phase. However, transport and magnetotransport properties of GaSb-MnSb samples depends on both components. In general, low temperature magnetotransport is dominated by the contribution of the GaSb matrix, while at room temperature measured data are qualitatively similar to those for pristine MnSb polycrystals. Additive character of these contributions along with the absence of any magnetooptical response besides that characteristic for bulk MnSb polycrystals suggests that these composites do not contain any considerable fraction of nm-sized ferromagnetic inclusions. Nevertheless, our results suggests that bulk GaSb-MnSb nanocomposite can be obtained, e.g. by more aggressive quenching.

The spectral, temperature, and magnetic field dependences of the magneto-optical transversal Kerr effect (TKE) have been studied along with the optical spectra of InFeAs layers formed by ion implantation with further pulsed laser melting at different laser pulse energies. A strong dependence of the magneto-optical and optical properties of InFeAs layers on the pulse energy has been revealed. The TKE spectra of the specimen formed at a minimum pulse energy ( W = 0.1 J/cm 2 ) indicate the presence of ferromagnetic (In, Fe)As nanoclusters with a Curie temperature of ≈180 K in the weakly doped semiconductive matrix and the absence of secondary magnetic phases. The TKE spectra of layers formed at W = 0.15–0.4 J/cm 2 are a superposition of the contributions from ferromagnetic (In,Fe)As nanoareas distributed in the volume and near-surface Fe inclusions. The predominance of the iron contribution in the spectra indicates the intensification of Fe diffusion towards the surface with an increase in the laser pulse energy. Anisotropy in the magneto-optical and optical spectra confirms anisotropic chemical phase separation in the layers.

In this paper, the spectral dependences of the transverse Kerr effect (ТКЕ) are studied experimentally and theoretically. The results are obtained for deposited and annealed samples with a corresponding variation in the size of the granules. It was found that thermomagnetic annealing leads to an increase in the ТКЕ value in magnetic nanostructures, while the most noticeable changes in the effect value were observed in the range of medium and high concentrations of the magnetic component in the visible region of the spectrum. The expediency of using the effective medium approach for calculating magneto-optical effects in granular systems, taking into account the size distribution of granules within the lognormal distribution of granules, is shown. Based on this approach, the main features of the optical and magneto-optical properties of nanocomposites are explained by the example of (Co45Fe45Zr10)X(Al2O3)1–X. All calculations are performed in the Bruggemann approximation, which effectively describes the properties of nanostructures in the region of average concentrations. Size effects are clearly manifested in nanocomposites and have a significant impact on the optical and magneto-optical properties of nanocomposites, especially in the IR region of the spectrum, which is associated with intraband transitions. Taking into account the particle size distribution makes it possible to significantly improve the description of such promising inhomogeneous nanostructures. The solved problem is very important and relevant both from the fundamental point of view – the study of magneto-optical, optical and transport phenomena in nanocomposites – and from the point of view of the great possibilities of their application in modern electronics and nanoelectronics. Taking into account the size effects and the particle size dispersion makes it possible to find new promising functional materials and control their properties in a wide spectral range.

A method is described for simultaneous control of the magnetic field intensity of reflected and transmitted unpolarized light in films of magnetics with giant magnetoreflection and magnetotransmission effects. The advantages of the proposed method over the methods of separate control of the intensity of transmission or reflection of light are shown. The spectral, temperature and dynamic ranges of application of the method are described on the example of thin films of doped lanthanum manganites.

A method for simultaneous controlling the intensity of reflected and transmitted light in magnetic films possessing giant magnetoreflection and magnetotransmission is described. Advantages of this method over the separate approaches to controlling the intensity of reflection and transmission are demonstrated. The spectral, temperature, and dynamic ranges of using the proposed method are described using the example of lanthanum manganite films.

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.

Abstract—Spectral and temperature dependences of the magneto-optical transversal Kerr effect (TKE) of GaMnAs layers prepared by different methods are reported in this work. The GaMnAs layers prepared by pulsed laser sputtering at 300°С demonstrate a ferromagnetic behavior below 80 K, which is due to the presence of local ferromagnetic (Ga,Mn)As areas in the paramagnetic matrix. The Ga(In)MnAs layers prepared by ion implantation and subsequent pulsed laser annealing were found to exhibit a high TKE response at low temperatures. The presence of the characteristic band in the TKE spectrum in the range of transitions near the L point of the band structure of Ga(In)As confirms the intrinsic ferromagnetism. The temperature dependences of TKE measured for different spectrum ranges demonstrate nonmonotonic behavior, which indicates the magnetic inhomogeneity of the layers. The peculiarities of the magneto-optical spectra of GaMnAs, which were not observed previously, were explained by taking the magnetic and phase inhomogeneity of the layers into account. The sensitivity of TKE to the phase inhomogeneity of the Ga(In)MnAs layers and the efficiency of TKE in studying the electron spectrum and magnetic structure of diluted magnetic superconductors are demonstrated.