Jan Manak

Czech Academy of Sciences, Institute of Physics | FZU · Department of Material Analysis

Type-II multiferroics, where spin interactions induce a ferroelectric polarization, are interesting for new device functionalities due to large magnetoelectric coupling. We report on a new type of multiferroicity in the quadruple-perovskite $\text{BiMn}_{\text{3}}\text{Cr}_{\text{4}}\text{O}_{\text{12}}$, where an antiferromagnetic phase is induced...

Laser Shock Peening (LSP) is a surface treatment technique for metallic materials. It induces plastic deformation at the surface of up to around 1 mm in depth. This process introduces residual stresses that lead to strain hardening, and potentially improvements in fatigue, stress corrosion cracking (SCC) and general corrosion behaviour in many, but...

Charge Confinement Electron motion inside nanostructures is strongly influenced by the presence of surfaces. In article number 2107403, Petr Kužel and co‐workers apply time‐resolved near‐field and far‐field terahertz spectroscopy and quantum‐mechanical calculations to study the conductivity in an array of aligned high‐quality GaAs nanobars. The stu...

Arrays of ultimate‐quality single‐crystalline GaAs nanobars are prepared via electron‐beam lithography in a molecular‐beam‐epitaxy‐grown GaAs layer transferred onto an electrically insulating and optically and terahertz transparent sapphire substrate. Measurements of ultrafast terahertz photoconductivity at 300 and 20 K in an array of such aligned...

The complex study of the mechanical properties of pure iron produced by selective laser melting (SLM) revealed enhanced values of the yield stress and ultimate tensile strength as compared to the material produced in a classic way. These values result from high dislocation density, presence of interstitial carbon and small precipitates. In-situ ten...

The paper investigates deformations and plastic properties received from different material volumes and tests of magnesium samples. Small volume characteristics gained on single Mg crystals are compared to polycrystalline AZ31 alloy. Results of tests employing nanoindentation, focused ion beam milling and electron backscatter diffraction techniques...

The thermomechanical processing by equal-channel angular pressing (ECAP) is used for certain metals and alloys in order to make their structure fine and to increase material strength. In the previous study done at our institute, grade 2 titanium was successfully processed using four consecutive route A passes via a 90 ° ECAP die with high backpress...

Diamond optical centers emerged recently as promising single-photon sources for quantum photonics. Particularly, negatively charged silicon vacancy (SiV⁻) centers show great promise due to their narrow zero-phonon emission line present also at room temperature. However, due to fabrication tolerances it is challenging to prepare directly photonic st...

Zinc and its alloys belong to a group of biodegradable materials, which can be potentially used for the preparation of temporary orthopedic implants. The research of biodegradable zinc materials revealed a lot of limitations; however, the new processing approaches of those materials can enhance their properties, which are insufficient for now. In t...

High frequency acoustic emission monitoring is proving a useful technique in improving the understanding of deformation processes occurring in nano- and micro-scale mechanical contacts. In this study AE monitoring has been used to investigate the fracture of alumina and MgO-partially stabilized zirconia (PSZ) at high strain rate in repetitive nano-...

Zinc-based alloys containing the elements of the second group of the periodic table have been extensively studied as potential candidates for applications as a biodegradable material. In this study, the ZnMg0.8Ca0.2 (wt%) alloy was prepared and treated by annealing and extrusion at various conditions. The evolution of microstructure and mechanical...

Nanoindentation is used for characterization of small scale material properties of hydrated cement. It is employed as a precise loading tool on samples fabricated with Focused Ion Beam milling (FIB). The effect of heat on the microstructure of cement during different FIB energy loads is studied. Milling currents as low as 0.1 nA can be considered a...

Despite the current focus on the electronic properties of GaV4S8 lacunar spinel, the microstructural and mechanical characterization of this material is scarce in the literature. In this work, we propose an effective GaV4S8 ceramics production method and provide a detailed microstructural and micromechanical characterization. Light microscopy, scan...

This paper deals with the investigation of optical and electrical properties of Co3O4. Their impact on catalytic activity in ethanol dehydrogenation is observed. The change in conductivity is provided by intentionally heating the samples in-situ, variation of oxygen flow rate, introduction of the forming gas (10% H2 in N2) and the application of di...

Low temperature shape setting superelastic ribbon

In Cu–Ni–Al shape memory alloy, we observed a significant size effect on the twinning stress, i.e. the dependency of compression stress needed for twin-variant reorientation on sample size using in situ loading of micro- and nanoscale pillars in scanning and transmission electron microscopes. With decreasing dimensions of pillars, the twinning stre...

The paper focuses on quantifying of vacuum and heat influence as unavoidable effects that appear during preparation and in-situ monitoring of micromechanical performance of cement pastes. Experimental tests at micrometer scale employ microscopic techniques of Scanning Electron Microscopy (SEM) and Focused Ion Beam (FIB). High vacuum is applied to s...

Demonstration of the existence of a strong size effect on the twinning stress during twin reorientation upon compression from micro to nanoscale pillars in Cu–Ni–Al shape memory single crystal.

Zinc-based materials alloyed with the elements of the 2nd group of the periodic table have been studied as potential materials for the fabrication of various biodegradable implants. In this study, we prepared two ternary alloys: ZnMg0.8Ca0.2 (wt.%) and ZnMg0.8Sr0.2 by melting a mixture of pure elements and subsequent gravity casting. We studied the...

This paper presents a numerical simulation of a micro-scale experiment on a magnesium alloy. Micro cantilever beams were fabricated using Focused Ion Beam technology in a single crystal of Mg. The cantilever beams have dimensions in the order of a few micrometers and a pentagonal cross section. Nanoindenter was used for cantilever beam bending and...

The paper shows results of microscale experimental tests performed on cement paste specimens fabricated by focused ion beam milling. The specimens are prepared in the form of cantilever beams and loaded in bending by nanoindenter. The dimensions of specimens are in the order of a few micrometers which corresponds to the single phase size. Intact an...

Gradient of hardness and Young’s modulus over cross section of laser annealed NiTi wires

In the present study, in situ microbending experiments on magnesium single crystalline microcantilevers are presented. Microcantilevers with pentagonal cross-section were fabricated by focus ion beam. Two basic crystallographic orientations of the microcantilevers were investigated: {0001} and {10-10}, i.e., the c-axis perpendicular to and parallel...

Amorphous silicon carbide (a-SiC) flms are promising solution for functional coatings intended for harsh environment due to their superior combination of physical and chemical properties and high temperature stability. However, the structural applications are limited by its brittleness. The possible solution may be an introduction of nitrogen atoms...

The scratch test, as probably the most widespread technique for assessment of the adhesive/cohesive properties of a film–substrate system, fully depends on reliable evaluation based on assessment of critical loads for systems’ failures. Traditionally used evaluation methods (depth change record and visual observation) may sometimes give misleading...

Polycrystalline diamond-based photonic crystal slabs were designed using computer simulation and fabricated employing optimized focused ion beam milling technique. Such samples could be used to control light emission from diamond optical centers.

Diamond-like carbon (DLC) layers with amorphous structure are frequently used as tribological and protective coatings in various applications. The resulting properties these DLC layers are driven by their structure and composition. The desired structure is a homogeneous layer with very smooth surface to minimize the friction and wear of components....

In this work, correlation between nanomechanical properties and crystallographic orientation of grains in 99.9 % magnesium is presented. Crystallographic orientation of individual grains was obtained by scanning electron microscope (SEM) equipped with electron backscatter diffraction (EBSD) detector. Hardness and elastic modulus of grains with know...

The anisotropic nanomechanical properties of AZ31 magnesium alloy and pure Mg were measured in situ via nanoindentation of individual grains with simultaneous observations using a scanning electron microscope. Values of the nanohardness, indentation size effect, elastic modulus, and yield strength were correlated with the crystallographic orientati...

Every material is structured in its unique way and has its own recognizable microstructure. There are a number of approaches in establishing the relationship between mechanical properties and microstructure of a material, but none of them is universal and correlation free, probably because of luck of attention to the sub-grain structure. The possib...