arXiv subjects

Vasily Moshnyaga

Publications and source records attributed to Vasily Moshnyaga.

9 recordsLinked to original sources

arXiv2025

Nanoscale friction of manganite superlattice films controlled by layer thickness and fluorine content

We investigate nanoscale friction in [LaMnO3]m/[SrMnO3]n superlattice films using lateral force microscopy, focusing on the effects of fluorine doping and top-layer thickness. For all samples, friction forces scale linearly with the sum of the applied normal and adhesion forces. While friction forces vary spatially due to local adhesion fluctuations, the friction coefficient remains position independent for each specimen. It is, however, systematically influenced by fluorine concentration and top-layer thickness. Our data indicates that frictional energy dissipation extends up to 5 nm beneath the surface, demonstrating a clear dependence on subsurface structure. We attribute this to viscoelastic dissipation within the stress field and evanescent waves generated by the sliding tip, which can quantitatively account for the observed friction coefficients. These results show that, once adhesion is properly accounted for, the friction coefficient is a reproducible material property that can be tuned via controlled modifications to surface and subsurface layers.

cond-mat.mtrl-sci↗

arXiv2025

Engineering of electronic and magnetic modulations in gradient functional oxide heterostructures

Advanced interface engineering provides a way to control the ground state of correlated oxide heterostructures, which enables the shaping of future electronic and magnetic nanodevices with enhanced performance. An especially promising and rather new avenue is to find and explore low-dimensional phases of structural, ferroic and superconducting origin. In this multimodal study, we present a novel dynamic growth control method that enables synthesizing compositionally graded superlattices (SLs) of (LaMnO_3)_10/(SrMnO_3)_10 (LMO/SMO), in which the layers gradually change their composition between LMO and SMO with gradient G values ranging from 0 to 100 %. This leads to strong modulations in the material's electronic properties and of the two-phase ferromagnetic (FM) behavior. In particular, we observe that G has almost no impact on the emergent high-temperature FM phase; in contrast, the low-temperature volume-like FM phase increases drastically with higher G-factors and thus can serve as a precise marker for chemical composition on a nanoscale. Focusing on the interfacial charge transfer found at sharp SMO/LMO interfaces (G=0), we observe that for higher G-factors a long-range charge modulation develops, which is accompanied by an insulator-to-metal transition. These findings showcase G as a crucial control parameter that can shape the superlattice's intrinsic properties and provide a perspective for designing functional oxide heterostructures with artificially disordered interfaces.

cond-mat.mtrl-sci↗

arXiv2023

Dynamics of electronic phase separation at the laser-induced insulator-metal transition in (La$_{0.6}$Pr$_{0.4}$)$_{0.7}$Ca$_{0.3}$MnO$_3$

Ultrafast optical excitations allow creating new metastable and hidden states in quantum materials. However, the fundamental material properties required to support new emergent order are largely unknown. Here we show for two colossal magnetoresistive (CMR) manganites that electronic phase separation (EPS) strongly favors non-thermal behavior and exploit this to stabilize an optically-induced conducting state. Our results shed light on the role of EPS in optical control of CMR manganites and provide guidance for the design of materials that can exhibit non-equilibrium states of matter.

cond-mat.str-el↗

arXiv2022

Nanoscale friction controlled by top layer thickness in [LaMnO$_{3}$]$_{m}$/[SrMnO$_{3}$]$_{n}$ superlattices

We conducted lateral force microscopy measurements on seven [LaMnO$_{3}$]$_{m}$/[SrMnO$_{3}$]$_{n}$ superlattices with varied layer thicknesses. We observe that the friction forces and the friction coefficients initially increase with increasing LaMnO3 top layer thickness, followed by saturation when the top layer thickness exceeds a few nanometers. These observations clearly demonstrate that sliding friction is affected by sub-surface material properties to a depth of several nanometers and is not just determined by dynamics in the contact interface. We argue that the sub-surface dissipated energy is governed by damping in the elastically strained volume below the AFM tip, an effect which we estimate via thermoelasticity. The absence of a correlation between friction and the thermal resistivity of our superlattices shows furthermore that high-frequency phonons and heat conduction do not play a role in determining friction. Our observations thus demonstrate that friction can be tailored by sub-surface material properties.

cond-mat.mtrl-sci↗

arXiv2021

Coherent phonon transport and minimum of thermal conductivity in LaMnO$_3$/SrMnO$_3$ superlattices

In this Letter, we present investigations of thermal transport in (LaMnO$_3$)$_n$/(SrMnO$_3$)$_n$ superlattices (SLs) with SL periods $Λ=2n$ between $2$ and $12$ unit cells. The analysis of the experimental data clearly reveals a minimum in the thermal conductivity $κ$ at $Λ=6$ u.c. Furthermore, we theoretically estimate the phonon mean free path to be about $3Λ$ in our SLs. These findings clearly show that, in a wide temperature range of $\pm 100\,$K around room temperature, thermal transport in our manganite SLs is coherent. In addition, we demonstrate that antiferromagnetic magnetic ordering can control the degree of coherency. This opens the challenging perspective for active control of coherent transport in correlated matter.

cond-mat.mtrl-sci↗

arXiv2021

Angular dependence of Hall effect and magnetoresistance in SrRuO$_3$-SrIrO$_3$ heterostructures

Perovskite SrRuO$_3$ is a prototypical itinerant ferromagnet which allows interface engineering of its electronic and magnetic properties. We report synthesis and investigation of atomically flat artificial multilayers of SrRuO$_3$ with the spin-orbit semimetal SrIrO$_3$ in combination with band-structure calculations with a Hubbard $U$ term and topological analysis. They reveal an electronic reconstruction and emergence of flat Ru-4d$_{xz}$ bands near the interface, ferromagnetic interlayer coupling and negative Berry-curvature contribution to the anomalous Hall effect. We analyze the Hall effect and magnetoresistance measurements as a function of the field angle from out of plane towards in-plane orientation (either parallel or perpendicular to the current direction) by a two-channel model. The magnetic easy direction is tilted by about $20^\circ$ from the sample normal for low magnetic fields, rotating towards the out-of-plane direction by increasing fields. Fully strained epitaxial growth enables a strong anisotropy of magnetoresistance. An additional Hall effect contribution, not accounted for by the two-channel model is compatible with stable skyrmions only up to a critical angle of roughly $45^\circ$ from the sample normal. Within about $20^\circ$ from the thin film plane an additional peak-like contribution to the Hall effect suggests the formation of a non-trivial spin structure.

cond-mat.str-el↗

arXiv2021

Ultrafast element-resolved magneto-optics using a fiber-laser-driven extreme ultraviolet light source

We present a novel setup to measure the transverse magneto-optical Kerr effect in the extreme ultraviolet spectral range at exceptionally high repetition rates based on a fiber laser amplifier system. This affords a very high and stable flux of extreme ultraviolet light, which we use to measure element-resolved demagnetization dynamics with unprecedented depth of information. Furthermore, the setup is equipped with a strong electromagnet and a cryostat, allowing measurements between 10 and 420 K using magnetic fields up to 0.86 T. The performance of our setup is demonstrated by a set of temperature- and time-dependent magnetization measurements showing distinct element-dependent behavior.

physics.optics↗

arXiv2018

Layer-by-layer resistive switching: multi-state functionality due to electric-field-induced healing of "dead" layers

Materials exhibiting reversible resistive switching in electrical fields are highly demanded for functional elements in oxide electronics. In particular, multilevel switching effects allow for advanced applications like neuromorphic circuits. Here we report on a structurally driven switching mechanism involving the so-called `dead layers' of perovskite manganite surfaces. Forming a tunnel barrier whose thickness can be changed in monolayer steps by electrical fields, the switching effect exhibits well-defined and robust resistive states.

cond-mat.mtrl-sci↗

arXiv2017

In situ monitoring of atomic layer epitaxy via optical ellipsometry

We report on the use of time-resolved optical ellipsometry to monitor the deposition of single atomic layers with subatomic sensitivity. Ruddlesden-Popper thin films of SrO(SrTiO3)n=4 were grown by means of metalorganic aerosol deposition in the atomic layer epitaxy mode on SrTiO3(100), LSAT(100) and DyScO3(110) substrates. The measured time dependences of ellipsometric angles, $Δ(t)$ and $Ψ(t)$, were described by using a simple optical model, considering the sequence of atomic layers SrO and TiO2 with corresponding bulk refractive indices. As a result, valuable online information on the growth process, the film structure and defects were obtained. Ex situ characterization techniques, i.e. transmission electron microscopy (TEM), X-ray diffraction (XRD) and X- ray reflectometry (XRR) verify the crystal structure and confirm the predictions of optical ellipsometry.

cond-mat.mtrl-sci↗