Films of metal-insulator nanogranular composites M x D 100 – x with different composition and percentage of metal and dielectric phases (M = Fe, Co, CoFeB; D = Al 2 O 3 , SiO 2 , LiNbO 3 ; x ≈ 15–70 at %) are investigated by magnetic resonance in a wide range of frequencies ( f = 7–37 GHz) and temperatures ( T = 4.2–360 K). In addition to the usual ferromagnetic resonance signal from an array of nanogranules, the experimental spectra contain an additional absorption peak, which we associate with the electron paramagnetic resonance (EPR) of Fe and Co ions dispersed in the insulating space between the granules. In contrast to the traditional EPR of Fe and Co ions in weakly doped non-magnetic matrices, the observed peak demonstrates a number of unusual properties, which we explain by the presence of magnetic interactions between ions and granules.

In memory of Aleksandr Fedorovich Andreev, Dmitriev V.V., Kagan M.Yu., Kamenskii V.G., Kats E.I., Kveder V.V., Kreines N.M., Lebedev V.V., Marchenko V.I., Melnikovsky L.A., Smirnov A.I., Suslov I.M., Fomin I.A., Edel’man V.S.

In memory of Lev Petrovich Pitaevskii, Andreev A.F., Gershtein S.S., Gurevich A.V., Dmitriev V.V., Kreines N.M., Liberman M.A., Meierovich B.E., Pokrovsky V.L., Ritus V.I., Ryutova M.P., Starobinskii A.A., Feigel’man M.V., Fomin I.A., Chaplik A.V.

Films of metal–insulator nanogranular (CoFeB)x(LiNbO3)100 – x and (CoFeB)x(Al2O3)100 – x composites with different content x of a ferromagnetic metallic phase have been investigated by the magnetic resonance method in a wide temperature range (4.2–360 K). The systems under study are characterized by a high concentration of paramagnetic Fe and Co ions, which are dispersed in the insulating medium between ferromagnetic CoFeB granules. The experimental spectra of these systems show a peak of ferromagnetic resonance associated with the ferromagnetic granule array and an additional less intense absorption peak associated with the electron paramagnetic resonance of Fe3+ ions in the insulating matrix. It has been found that the position and intensity of this peak depend on the composition of the system and temperature. The observed behavior is explained by existence of exchange interaction between magnetic ions and ferromagnetic granules.

The room-temperature magnetic resonance spectra of metal–insulator (CoFeB)x(LiNbO3)100 – x and (CoFeB)x(Al2O3)100 – x nanogranular composite films with various ferromagnetic metallic phase contents x near the percolation threshold are investigated. The systems under study are characterized by a high concentration of paramagnetic ions dispersed in an insulator matrix between ferromagnetic granules. In addition to a usual ferromagnetic resonance signal, these films are found to exhibit an additional absorption peak in weak fields. In contrast to the usual ferromagnetic resonance excited by a transverse high-frequency magnetic field, the additional peak demonstrates a weak dependence of its amplitude on the resonance excitation geometry. The position of this peak depends on the composition of the system, the resonance excitation frequency (f = 7–38 GHz), and the magnetic field orientation with respect to the film plane. This behavior is associated with the paramagnetic resonance of Fe3+ ions, which are present in the insulator matrix and interact with ferromagnetic granules.

theoretical physicist and corresponding member of the Russian Academy of Sciences (RAS), Igor Ekhiel'evich Dzyaloshinskii. A disciple and colleague of the legendary Lev Davidovich Landau, one of the founders of the Institute of Theoretical Physics (ITP) of RAS, editor of the journal Zhurnal Eksperimental'noi i Teoreticheskoi Fiziki (ZhETF Ð J. Exp. Teor. Phys.) and Pis'ma v ZhETF (JETP Lett.), professor at Moscow Institute of Physics and Technology (MIPT), the faculty of Mechanics and Mathematics of Lomonosov Moscow State University (mech.math. MSU), and theUniversity of California, Irvineì this is a short list of highlights in the scientiéc biography of Igor Ekhiel'evich. The scientific interests of Dzyaloshinskii cover the whole spectrum of condensed media theory; most of his papers have been widely recognized. Already in his younger days, Dzyaloshinskii became a leader in the community of the physics of magnetic phenomena and presented such results as the prediction of the `magnetoelectric effect,' the introduction of the `Dzyaloshinskii ±Moriya interaction,' and the theory of helical superstructures and commensurability effects. This topic is in the list of his publications for today: the epoch of multiferroics that came in the 2000s was, in fact, based on the predictions made more than half a century before by the young scientist I E Dzyaloshinskii. These studies were included in the candidate thesis Dzyaloshinskii defended in 1957. When speaking at the defense, Landau, who was not lavish in giving praise, said that Dzyaloshinskii was one of the most talented young theoreticians whom he had met in recent years. During that same time, the temperature diagram technique was developed. It was included in the written (together with A A Abrikosov and L P Gor'kov) handbook of several generationsÐMethods of Quantum Field Theory in Statistical PhysicsÐthat was awarded the 1989 L D Landau Prize. The book (``AGD'' or the ``Green Book'' as referred to by many generations of students, postgraduates, and research workers at ITP) laid foundation of the scientific language used to date by theoretical physicists around the world. The fundamental contributions due to Igor Ekhiel'evich involve the microscopic theory of van der Waals forces, onedimensional systems of interacting particles, quantum liquids and crystals, spin glasses, topological defects in magnets and liquid crystals (incidentally, it was precisely Dzyaloshinskii who introduced in Russian theoretical physics the idea that liquid crystals are an important area of application of general principles), exactly solvable models, an original renormalization group for high-temperature superconductors, states with time reversal symmetry violation. The scientific and pedagogical achievements of I E Dzyaloshinskii are well known and, in particular, were described in detail in previous well wishes marking milestones. It so happens that most of us (disciples and colleagues of I E Dzyaloshinskii) took part in these very celebrations in the journal Uspekhi Fizicheskikh Nauk (UFN) (see UFN 162 (1) 139 (1992); UFN 171 (2) 227 (2001); UFN 181 (2) 231 (2011)) (Physics±Uspekhi 35 (1) 49 (1992), Physics±Uspekhi 44 (2) 213 (2001), Physics±Uspekhi 54 (2) 221 (2011)). However, new interesting and important work by Dzyaloshinskii appeared recently. In particular, noteworthy are two of his studies that predicted theoretically (and then revealed experimentally using muon spectroscopy methods in an etalon Cr2O3 magnetoelectric) a very interesting and nontrivial phenomenon. Namely, it turns out that, in a certain geometry, electric charges induce a magnetic field with quadrupole and monopole symmetry on a magnetoelectric antiferromagnet surface, both in the sample itself and in the surrounding space. I E Dzyaloshinskii continues to work and, in this milestone year, is finishing preparation of a paper, in collaboration with an international group of experimentalists, on the inverse electrocaloric effect in ion liquids (predicted theoretically in an earlier study undertaken by Dzyaloshinskii and Obukhov). Uspekhi Fizicheskikh Nauk 191 (2) 223 ± 224 (2021) Translated by M V Tsaplina PERSONALIA PACS number: 01.60.+q

Metal-insulator nanocomposite (CoFeB)x(LiNbO3)1−x films are studied by the ferromagnetic resonance method in the temperature range of 4–320 K. In the low-temperature region, the maximum of the ferromagnetic resonance linewidth and a negative dynamic shift of the absorption peak, typical of the mechanism of slow ion relaxation on magnetic impurities, are found. The observed magnetic relaxation features can be caused by paramagnetic Co and Fe ions, which are dispersed in the dielectric LiNbO3 matrix and are exchange-coupled to ferromagnetic CoFeB granules. Experimental temperature dependences of the ferromagnetic resonance linewidth and shift are in good agreement with theoretical curves obtained within the proposed approach.

Mathematical Sciences, and author of numerous reviews in Uspekhi Fizicheskikh Nauk (UFN) [Physics±Uspekhi] journal, Moisei IsaakovichKaganov, passed away onAugust 31, 2019 at the age of 98. Moisei Isaakovich became famous for his brilliant work on the physics of metals and dielectrics and the physics of magnetic phenomena. His scientific style was characterized by a broad view of the subject under study, an original approach to problems, and an independent way of thinking. Moisei Isaakovich will also remain in our memory as a remarkable popularizer of science. In his popular scientific books and papers, he comprehensively presented contemporary scientific problems and achievements for a wide range of readers and, which is particularly important, infected many generations of the readers of the journal Kvant (Quantum) with his love of science and cognition of the world. Moisei Isaakovich Kaganov (MIK) was born on June 4, 1921 in Kharkov. In 1939, he was admitted as a student to the Department of Physics at the Kharkov State University, but his studies did not last long. In December of the same year, MIK was conscripted into the army. He was in the war from beginning to end, serving till early 1946. In 1946, MIK returned to the university and, having done two diploma studies with his fellow student Viktor Moiseevich Tsukernik, graduated in 1949. This work and friendship between students were the beginning of their years-long fruitful collaboration in a whole number of fields, mainly in the theory of magnetic phenomena. The subject of one study about absorption of electromagnetic radiation by a spin wave system was proposed by Aleksandr Ilyich Akhiezer, and another one concerning the permittivity of a polycrystal was proposed by Ilya Mikhailovich Lifshitz. MIK considered I M Lifshitz to be his teacher. The cooperation with I M Lifshitz lasted many years and with time transformed into a strong friendship. Simultaneously, MIKworked a long time together with A I Akhiezer. In October of 1949,MIK began working at the Ukrainian Institute of Physics and Technology (UIPT), where he remained till April 1970. In 1970, invited by P L Kapitza, he and I M Lifshitz left for Moscow for the Institute of Physical Problems (IPP, now Kapitza Institute), where he worked for 24 years until his retirement in 1994. Both in Kharkov and in Moscow, MIK combined his scientific work with teaching activity. He first taught at Kharkov State University and then became a professor at Lomonosov Moscow State University, where he delivered courses on the electron theory of metals and quantum solid-state theory, both very popular with students. After MIK retired in 1994, he went to Boston in the USA, where one of his daughters had settled. The range of MIK's scientific interests spanned from the problems of classical electrodynamics of continuum media to practical problems of the physics of metals. In the early 1950s, at the cryogenic laboratory of UIPT, experiments on solidstate physics were started, and MIK, together with I M Lifshitz, got involved in the electron theory of metals. This became a basic subject for MIK for many years. One of his first papers in this field that became widely known was ``Kinetics of superconductivity destruction'' (I M Lifshitz, M IKaganov,Dokl. Akad. Nauk SSSR, 1953, v. 90, p. 579), in which the authors calculated the electromagnetic field distribution in a layer of normal metal emerging on a sample surface when superconductivity gets destroyed. In a normal metal layer, either a normal or an anomalous skin effect is realized, depending on the field oscillation frequency and the electron free path. According to MIK, he got to take part in that study as an expert on the anomalous skin effect. MIK returned to the skin effect time and again. Together withMYa Azbel', he formulated the theory of an anomalous skin effect in metals with an arbitrary electron spectrum (Dokl. Akad. Nauk SSSR, 1955, v. 102, p. 49). Together with VMTsukernik, he solved the problem of the influence of thermoelectric forces on the skin effect in metals (Zh. Eksp. Teor. Fiz., 1958, v. 35, p. 474 [Sov. Phys. JETP, 1959, v. 8, Uspekhi Fizicheskikh Nauk 190 (2) 221 ± 222 (2020) Translated by M V Tsaplina PERSONALIA PACS number: 01.60.+q

Metal-insulator (CoFeB)(x)(LiNbO3)(100-x), nanocomposite films with different content of the ferromagnetic (FM) phase x are investigated by ferromagnetic resonance (FMR) technique. A strong change of the FMR line shape is observed in the vicinity of metal-insulator transition (MIT) of the film, where the hopping-type conductivity sigma modifies to the regime of a strong intergranular tunnelling, characterized by a logarithmic dependence sigma(T) at high temperatures. It is shown that below MIT, the FMR linewidth is mainly determined by the inhomogeneous distribution of the local anisotropy axes in the film plane. Above MIT, the contribution of this inhomogeneity to the line broadening decreases. At the same time, two-magnon magnetic relaxation processes begin to play a significant role in the formation of the linewidth. The observed behaviour indicates the critical role of interparticle exchange in the tunnelling regime above MIT of the nanocomposite.

Static and dynamic magnetic properties of a ferrimagnetic [Fe(35 angstrom)/Gd(50 angstrom)](12) superlattice were investigated in a wide 4-300 K temperature range using magneto-optical Kerr effect (MOKE) and ferromagnetic resonance (FMR) techniques. The multilayer structure was sputtered on a transparent glass substrate which made it possible to perform MOKE measurements on both Fe and Gd terminated sides of the superlattice. These experiments allowed us to detect a transition between field-aligned and canted magnetic states on both sides of the film and to distinguish between the bulk and surface twisted phases of the superlattice. As a result, the experimental H - T magnetic phase diagram of the system was obtained. FMR studies at frequencies 7-36 GHz demonstrated a complex evolution of absorption spectra as temperature decreased from room down to 4 K. Two spectral branches were detected in the sample. Theoretical simulations show that the observed spectral branches correspond to different types of inhomogeneous resonance modes in the multilayer with non-uniform magnetization precession inside Gd layers.

Metal-insulator (CoFeB)x(LiNbO3)100−x nanocomposite films with different content of the ferromagnetic (FM) phase x are investigated by ferromagnetic resonance (FMR) technique. A strong change of the FMR line shape is observed in the vicinity of metal-insulator transition (MIT) of the film, where the hopping-type conductivityσmodifies to the regime of a strong intergranular tunnelling, characterized by a logarithmic dependence σ(T ) at high temperatures. It is shown that below MIT, the FMR linewidth is mainly determined by the inhomogeneous distribution of the local anisotropy axes in the film plane. Above MIT, the contribution of this inhomogeneity to the line broadening decreases. At the same time, two-magnon magnetic relaxation processes begin to play a significant role in the formation of the linewidth. The observed behaviour indicates the critical role of interparticle exchange in the tunnelling regime above MIT of the nanocomposite.

In this work, we analyze the role of a thin Cr spacer between Fe and Gd layers on the structure and magnetic properties of a [Fe(35 Å)/Cr(tCr)/Gd(50 Å)/Cr(tCr)]12 superlattice. Samples without the Cr spacer (tCr = 0) and with a thin spacer (tCr = 4 Å) are investigated using X-ray diffraction, polarized neutron and resonance X-ray magnetic reflectometry, static magnetometry, magneto-optical Kerr effect, and ferromagnetic resonance techniques. Magnetic properties are studied experimentally in a wide temperature range 4–300 K and analyzed theoretically using numerical simulation on the basis of the mean-field model. We show that a reasonable agreement with the experimental data can be obtained considering temperature dependence of the effective field parameter in gadolinium layers. The analysis of the experimental data shows that besides a strong reduction of the antiferromagnetic coupling between Fe and Gd, the introduction of Cr spacers into Fe/Gd superlattice leads to modification of both structural and magnetic characteristics of the ferromagnetic layers.

Abstract —The effect of laser pulse energy E on the possibility of forming of a homogeneous “high-temperature” ferromagnetic phase in Mn_ x Si_1 – _ x ( x ≈ 0.5) alloy films grown by pulsed laser deposition onto an Al_2O_3 (0001) substrate has been studied. The high-temperature phase with manganese concentration x ≈ 0.53 and the Curie temperature T _C ~ 200–300 K is shown to form near the substrate at the initial stage of the film growth. In this case, high values E ≥ 6.8 J/cm^2 favor the stabilization of this phase over all film thickness, while low values E = 2.6–5.7 J/cm^2 lead to a decrease in the manganese concentration in the upper film layer and the formation of additional “low–temperature” phase with T _C ≈ 30–50 K provided by silicides MnSi and Mn_4Si_7 crystallites.