arXiv subjects

Ruslan Salikhov

Publications and source records attributed to Ruslan Salikhov.

11 recordsLinked to original sources

arXiv2026

Room-temperature magnon-phonon transduction in high-damping Co/Pt structures

Quantum communication and information processing strongly benefit from the coupling between different quasi-particles, offering complementary advantages. Magnetoelastic materials inherently allow for direct coupling between magnetization dynamics and quantized lattice vibrations, called phonons. Near the ferromagnetic resonances, phonons may thus trade energy and angular momentum with uniformly precessing magnetization, called magnons, and enable transduction of information from magnetic to phononic modes, thereby paving the way for long-range transport of magnetic information without the need of magnetic material. Here, we employ tailored magnetic-nonmagnetic heterostructures, which simultaneously act as cavities for standing shear waves, to bring selective phonons and magnons into resonance. These Co films with Pt seed layers show extended linewidth and reduced amplitude of the phonon-resonant FMR lines, providing a hallmark of energy and angular momentum exchange. Complementarily, by theoretical modeling and ultra-fast coherent phonon spectroscopy, we identify the responsible transverse acoustic phonons as standing shear waves in the combined Co and Pt structure. We find a high crystal quality in conjunction with a large magnetoelastic coupling constant as a prerequisite for efficient magnon-phonon coupling of this type. Such resonant enhancement of magnon-phonon coupling in CMOS-compatible material provides an ideal material platform for future quantum transducers.

cond-mat.mtrl-sci↗

arXiv2026

Chiral molecule-induced contributions to ferromagnetic resonance

Despite extensive research on chirality-driven spin selectivity, most studies have focused on static magnetic properties, while the influence of chirality on the dynamic magnetic response remains largely unexplored. Here, we investigate how chiral molecular interfaces affect magnetization dynamics in thin Co/Ni multilayers with perpendicular magnetic anisotropy using broadband ferromagnetic resonance spectroscopy. A comparison between bare (reference) films and molecule-functionalized (hybrid) samples reveals no measurable changes in either the resonance field or the linewidth that could be attributed to the presence of the chiral environment. Motivated by our findings we develop a macrospin description that distinguishes equilibrium modifications of the magnetic free-energy landscape (MIPAC-type effects) from non-equilibrium, CISS-induced spin torques. Our analysis shows that equilibrium modifications primarily shift the resonance condition via changes to the free energy landscape and thereby the effective field, whereas damping-like non-equilibrium torques provide a distinct channel for varying the effective damping rate. This approach establishes clear criteria for disentangling chiral-interface-induced energy modifications from torque-driven dynamical effects in ferromagnetic resonance experiments.

cond-mat.mtrl-sci↗

arXiv2026

Chiral Porphyrin Monolayers on Ferromagnetic Thin Films: Ultrafast Spectroscopy of Hybrid Interfaces

Hybrid ferromagnetic metal/organic interfaces (spinterfaces) exhibit unique properties, including spin filtering. In parallel, chiral organic molecules can themselves induce efficient spin filtering, leading to unexpectedly high spin polarizations. Here, we investigate how the proximity of gold-capped Co/Ni ferromagnetic multilayers influences the spectroscopic properties and photoinduced electron dynamics of chiral oligopeptides bearing a porphyrin chromophore. The molecules are covalently attached to the gold cap via a chiral linker, forming a self-assembled monolayer. The porphyrin macrocycles adopt an orientation parallel to the surface, resulting in the formation of J-like aggregates. Photoinduced dynamics are probed using femtosecond pump-probe transient absorption spectroscopy. Despite excitation of only a single molecular layer, a clear transient absorption signal of the porphyrin singlet excited state is observed. Adsorption on the metal surface leads to a pronounced reduction of the excited-state lifetime. However, no signatures of long-lived photoinduced charge-transfer products are detected. Furthermore, no dependence of the excited-state dynamics on either the magnetization direction of the ferromagnetic layer or the molecular chirality is observed.

cond-mat.mtrl-sci↗

arXiv2024

Ultrafast unidirectional spin Hall magnetoresistance driven by terahertz light field

The ultrafast control of magnetisation states in magnetically ordered systems is a key technological challenge for developing memory devices operable at picosecond timescales or terahertz (THz) frequencies. Despite significant efforts in ultrafast magnetic switching, convenient ultrafast readout of magnetic states remains under investigation. Currently, many experiments exploit magneto-optical effects for detecting magnetisation states, necessitating laser sources and optical components. However, energy-efficient and cost-effective electrical detection is preferred for practical applications. Unidirectional spin-Hall magnetoresistance (USMR) was proposed as a simple two-terminal geometry for the electrical detection of the magnetisation state in magnetic heterostructures. Here, we demonstrate that USMR is active at THz frequencies for picosecond time readouts, and can be initiated with light fields. We detect ultrafast USMR in various types of ferromagnet/heavy metal thin film heterostructures through THz second harmonic generation. Our studies, combined with temperature-dependent measurements of USMR, reveal a significant contribution from electron-magnon spin-flip scattering. This suggests possibilities for all-electrical detection of THz magnon modes.

cond-mat.mes-hall↗

arXiv2023

Spin-orbit interaction driven terahertz nonlinear dynamics in transition metals

The interplay of electric charge, spin, and orbital polarizations, coherently driven by picosecond long oscillations of light fields in spin-orbit coupled systems, is the foundation of emerging terahertz spintronics and orbitronics. The essential rules for how terahertz light interacts with these systems in a nonlinear way are still not understood. In this work, we demonstrate a universally applicable electronic nonlinearity originating from spin-orbit interactions in conducting materials, wherein the interplay of light-induced spin and orbital textures manifests. We utilized terahertz harmonic generation spectroscopy to investigate the nonlinear dynamics over picosecond timescales in various transition metal films. We found that the terahertz harmonic generation efficiency scales with the spin Hall conductivity in the studied films, while the phase takes two possible values (shifted by π), depending on the d-shell filling. These findings elucidate the fundamental mechanisms governing non-equilibrium spin and orbital polarization dynamics at terahertz frequencies, which is relevant for potential applications of terahertz spin- and orbital-based devices.

physics.app-ph↗

arXiv2023

Multilayer metamaterials with mixed ferromagnetic domain core and antiferromagnetic domain wall structure

Magnetic nano-objects possess great potential for more efficient data processing, storage and neuromorphic type of applications. Using high perpendicular magnetic anisotropy synthetic antiferromagnets in the form of multilayer-based metamaterials we purposely reduce the antiferromagnetic (AF) interlayer exchange energy below the out-of-plane demagnetization energy, which controls the magnetic domain formation. As we show via macroscopic magnetometry as well as microscopic Lorentz transmission electron microscopy, in this unusual magnetic energy regime, it becomes possible to stabilize nanometer scale stripe and bubble textures consisting of ferromagnetic (FM) out-of-plane domain cores separated by AF in-plane Bloch-type domain walls. This unique coexistence of mixed FM/AF order on the nanometer scale opens so far unexplored perspectives in the architecture of magnetic domain landscapes as well as the design and functionality of individual magnetic textures, such as bubble domains with alternating chirality.

cond-mat.mtrl-sci↗

arXiv2022

Control and tunability of magnetic bubble states in multilayers with strong perpendicular magnetic anisotropy at ambient conditions

The reversal of magnetic bubble helicity through topologically trivial transient states provides an additional degree of freedom that promises the development of multidimensional magnetic memories. A key requirement for this concept is the stabilization of bubble states at ambient conditions on application-compatible substrates. In the present work we demonstrate a stabilization routine for remanent bubble states in high perpendicular magnetic anisotropy [(Co(0.44\,nm)/Pt(0.7\,nm)]$_X$, X = 48, 100, 150 multilayers on Si/SiO$_2$ substrates by exploring the effect of external magnetic fields ($H_\mathrm{m}$) of different strength and angles ($θ$) with respect to the film surface normal. By systematic variation of these two parameters, we demonstrate that remanent bubble density and mean bubble diameter can be carefully tuned and optimized for each sample. Our protocol based on magnetometry only reveals the densest remanent bubble states at $H_\mathrm{m} = 0.87 H_\mathrm{s}$ ($H_\mathrm{s}$ is the magnetic saturation field) and $θ=60^\circ - 75^\circ$ for all $X$ with a maximum of 3736 domains/100 $μ$m$^2$ for the X = 48 sample. The experimental observations are supported by micromagnetic simulations taking into account the nanoscale lateral grain structure of multilayers synthesized by magnetron sputter deposition, and thus helping understand the different density of the bubble states found in these systems.

cond-mat.mtrl-sci↗

arXiv2021

Control of stripe domain wall magnetization in perpendicular anisotropy multilayers

We report on the controlled switching of domain wall (DW) magnetization in aligned stripe domain structures, stabilized in [Co (0.44 nm)/Pt (0.7 nm)]$_X$ ($X = 48$, 100, 150) multilayers with perpendicular magnetic anisotropy. The switching process, induced by an external magnetic field, is monitored by measuring the evolution of the in-plane magnetization. % We show that the remanent in-plane magnetization originates from the polarization of the Bloch-type DWs. With micromagnetic simulations, we reveal that the reversal of the DW polarization is the result of the emergence and collapse of horizontal Bloch lines within the DWs at particular strengths of the external magnetic field, applied opposite to the DW polarization. Our findings are relevant for DW-based magnonics and bubble skyrmion applications in magnetic multilayers.

physics.app-ph↗

arXiv2020

Specific Heat of Spin Excitations Measured by FerromagneticResonance

Using ferromagnetic-resonance spectroscopy (FMR), we investigate the anisotropic properties of epitaxial 3 nmPt/2 nmAg/10 nmFe/10 nmAg/GaAs(001) films in fully saturated meta-stable states at temperatures ranging from 70 K to 280 K. By comparison to spin-wave theory calculations, we identify the role of thermal fluctuation of magnons in overcoming the energy barrier associated with these meta-stable states. We show that the energy associated with the size of the barrier that bounds the meta-stable regime is proportional to the heat stored in the magnonic bath. Our findings offer the possibility to measure the magnonic contribution to the heat capacity by FMR, independent of other contributions at temperatures ranging from 0 K to ambient temperature and above. The only requirement being that the selected sample exhibits magnetic anisotropy, here, magnetocrystalline anisotropy.

cond-mat.mtrl-sci↗

arXiv2017

Micromagnetic Simulations for Coercivity Improvement through Nano-Structuring of Rare-Earth Free L1$_0$-FeNi Magnets

In this work we investigate the potential of tetragonal L1$_0$ ordered FeNi as candidate phase for rare earth free permanent magnets taking into account anisotropy values from recently synthesized, partially ordered FeNi thin films. In particular, we estimate the maximum energy product ($BH$)$_\mathrm{max}$ of L1$_0$-FeNi nanostructures using micromagnetic simulations. The maximum energy product is limited due to the small coercive field of partially ordered L1$_0$-FeNi. Nano-structured magnets consisting of 128 equi-axed, platelet-like and columnar-shaped grains show a theoretical maximum energy product of 228 kJ/m$^3$, 208 kJ/m$^3$, 252 kJ/m$^3$, respectively.

physics.comp-ph↗

arXiv2015

Enhanced and Tunable Spin-Orbit Coupling in Tetragonally Strained Fe-Co-B Films

We have synthesized 20 nm thick films of tetragonally strained interstitial Fe-Co-B alloys epitaxially grown on Au55Cu45 buffer layer. The strained axis is perpendicular to the film plane and the corresponding lattice constant c is enlarged with respect to the in-plane lattice parameter a. By adding the interstitial boron with different concentrations 0, 4, and 10 at.% we were able to stabilize the tetragonal strain in 20 nm Fe-Co films with different c/a ratios of 1.013, 1.034 and 1.02, respectively. Using ferromagnetic resonance (FMR) and x-ray magnetic circular dichroism (XMCD) we found that the orbital magnetic moment increases with increasing the c/a ratio, pointing towards the enhancement of spin-orbit coupling (SOC) at larger strain. Our results show that careful doping of ferromagnetic films allows to control the SOC by stabilizing anisotropic strain states. These findings are applicable in material design for spintronics applications. We also discuss the influence of B doping on the Fe-Co film microstructure, its magnetic properties and magnetic relaxation.

cond-mat.mtrl-sci↗