Szilárd Sajti

Wigner Research Centre for Physics · Department of Material Science by Nuclear Methods

The effect of laser irradiation in the energy range from 20 mW to 200 mW was investigated in 109 nm thick Fe51Rh49 film deposited on an MgO (100) substrate. The initial, A1 structure with fully paramagnetic magnetic ordering was achieved after irradiating the samples with 120 keV Ne+ ions with a fluence of 1 × 1016 ion/cm2, as it was confirmed by c...

FeRh based composite multiferroic materials have attracted great scientific interest due to their wide variety of possible applications in future nano device technology. In the recent work, a comprehensive study on the depth dependence of the metamagnetic phase transition in FeRh/BaTiO3 heterostructure is reported by means of single or combined ext...

We report on the depth dependence and technological limits of the phase transition of the iron rhodium alloy as function of temperature, external magnetic and electric fields in the FeRh/BaTiO3 multiferroic, determined by grazing-incidence nuclear resonant scattering measurements. The change of temperature induces a continuous and homogenous antife...

Time-of-flight in situ neutron reflectometry (i-NR) on Si/[57Fe(x nm)/natFe(x nm)]4/Pt with x = 4 and 8 nm multilayers during consecutive heat treatments at 423, 448, 473 and 498 K reveal an unexpected rearrangement of free volumes and an interface smoothening in the isotopic Fe multilayer below 473 K, before the regime of regular Bragg intensity d...

The multilayer of approximate structure MgO(100)/[nFe51Rh49(63 Å)/57Fe51Rh49(46 Å)]10 deposited at 200 °C is primarily of paramagnetic A1 phase and is fully converted to the magnetic B2 phase by annealing at 300 °C for 60 min. Subsequent irradiation by 120 keV Ne+ ions turns the thin film completely to the paramagnetic A1 phase. Repeated annealing...

Alpha-Synuclein (AS) is the protein playing the major role in Parkinson’s disease (PD), a neurological disorder characterized by the degeneration of dopaminergic neurons and the accumulation of AS into amyloid plaques. The aggregation of AS into intermediate aggregates, called oligomers, and their pathological relation with biological membranes are...

Nb/Fe/Nb vacuum evaporated trilayers were studies by X-ray reflectometry, Rutherford backscattering spectrometry and Mössbauer spectroscopy in order to obtain information on the properties of the Fe-on-Nb and Nb-on-Fe interfaces. According to the Mössbauer analysis the interfaces are rather sharp; chemical mixing forms less than 1 nm thick Fe-rich...

The Fe-on-Ti and Ti-on-Fe interfaces were studied experimentally by Mössbauer spectroscopy (MS), transmission electron microscopy (TEM) and x-ray reflectometry (XRR) on Ti/Fe/Ti trilayers grown on Si(111) substrates by vacuum evaporation. The nanoscale structure and composition were explored in cross sections using TEM, the layer structure and the...

For the stability of nanostructured materials, grain boundaries (GBs) can be controlled by the grain size. When the diffusion length Ld=(2Dt)1/2 is small compared to (~0.5 nm), the GB width, the volume diffusion at low temperature is slow compared to the GB diffusion (type-C regime), D being the volume diffusivity and t the isothermal annealing tim...

The chemical mixing at the Fe-on-Ti and Ti-on-Fe, i.e. the bottom and top interfaces of Fe in atomically deposited layers, were studied experimentally and by molecular dynamics simulations of the layer growth. The basic structure and chemical composition of the layers were explored in cross-sections using transmission electron microscopy. The calcu...

Electric field controlled ion transport and interface formation of iron thin films on a BaTiO3 substrate have been investigated by in situ nuclear resonance scattering and x-ray reflectometry techniques. At early stage of deposition, an iron-II oxide interface layer was observed. The hyperfine parameters of the interface layer were found insensitiv...

Reciprocity is when wave or quantum scattering satisfies a symmetry property, connecting a scattering process with the reversed one. While reciprocity involves the interchange of source and detector, it is fundamentally different from rotational invariance, and is a generalization of time reversal invariance, occurring in absorptive media as well....

Neutron supermirrors (SMs), the major components of neutron optical devices, are depth-graded d-spacing multilayers of several hundreds to several thousands of bilayers. The interface roughness is a major factor in the reflectivity of multilayers. This influence is especially significant if the number of bilayers is large. In this work, the interfa...

The instrumental concept of HERITAGE - a reflectometer with a horizontal sample geometry – well fitted to the long pulse structure of a neutron source is presented. It is constitutes a new class of reflectometers achieving the unprecedentedly high flux for classical specular reflectometry combined with off-specular reflectometry and grazing inciden...

The instrumental concept of HERITAGE - a reflectometer with a horizontal sample geometry - fitted to the long pulse structure of a neutron source is presented. It is dedicated on creating a new class of reflectometers achieving the unprecedentedly high flux for classical specular reflectometry combined with off-specular reflectometry and grazing in...

General expressions of the electron yield in (^{57})Fe integral conversion electron M\"ossbauer spectroscopy were derived depending on the angle of incidence of the (\gamma)-rays, on the source polarization and on the isotopic abundance of the source and the absober (blackness effects) using an exponential escape function of the electrons originati...

The thickness (d F) and concentration (x) dependence of the Curie temperature of Nix Cu1−x (d F) ferromagnetic alloy layers (x=0.55, 0.65, d F=[4.5 nm÷12 nm]) in contact with a vanadium layer was studied. The Curie temperature of the ferromagnetic layers depends on the thickness when it is comparable with the transition layer between the F and the...

The reflected neutron beam originating from a crystal monochromator contains higher order wavelength contributions. Multilayer mirror structures with various custom reflectivity curves including monochromatization and/or polarization of the neutron beam constitute a challenge in modern neutron optics. In this work, we present the study of three typ...

The setup, capabilities, and operation parameters of the neutron reflectometer GINA, the recently installed "Grazing Incidence Neutron Apparatus" at the Budapest Neutron Centre, are introduced. GINA, a dance-floor-type, constant-energy, angle-dispersive reflectometer is equipped with a 2D position-sensitive detector to study specular and off-specul...

Thickness (dF) and concentration (x) dependence of the Curie temperature of NixCu100-x(dF) ferromagnetic alloy layers (x =0.55,0.65, dF =[3nm{\div}12nm]) being in contact with a vanadium layer was studied. The Curie temperature of the ferromagnetic layers depends on the thickness when it is comparable with the interface layer between the F and the...

Reflected neutron beam originating from a crystal monochromator contains higher order wavelength contribution. Creating multilayer mirror structures with custom reflectivity curves including a monochromatic polarized neutron beam is a challenge in modern neutron optics. In this work we present the study of three types of magnetron-sputtered aperiod...

The continuous need towards improving the capacity of magnetic storage devices requires materials with strong perpendicular magnetic anisotropy. FePd, CoPd and their Co(Fe)Pt counterparts very attractive candidate for such purposes. The magnetic properties of these films are largely dependent on the orientation and local distribution of the L10 FeP...

L10 (CuAu(I)-type) ordered FePd as well as FePt and CoPt, due to their high magnetic anisotropy, are candidate materials for future ultra-high density magnetic recording. Atomic diffusion governs the structural relaxation and associated changes in the physical and magnetic properties in these alloys. Such processes involve diffusion paths of a few...

Layered superconducting ferromagnetic nanosystems Cu(32 nm)/V(40-80 nm)/Fe(0.5-4 nm)/MgO(001) have been investigated by reflectometry and the diffuse scattering of synchrotron radiation. The data obtained make it possible to determine the important characteristics of samples such as the layer thickness and the rms heights and lateral correlation le...

FePt, FePd, CoPt, and CoPd in equilibrium exhibit the L10 structure with high perpendicular magnetic anisotropy making them attractive candidates for high-density magnetic recording. Magnetic properties of these films depend on the distribution and orientation of the L10 fraction controlled by diffusion on atomic scale. Epitaxial isotope-periodic n...

Design, characterization, and selected applications of a novel electron detector dedicated to conventional perpendicular- and low-angle-incidence conversion electron Mössbauer spectroscopy are presented. The setup is suitable for varying the incident angle and external magnetic fields on Mössbauer source and absorber. Test experiments were performe...

In order to get accurate information about complex systems depending on a lot of parameters, frequently different experimental methods and/or different experimental conditions are used. The evaluation of these data sets is quite often a problem. The correct approach is the simultaneous fitting, which is rarely used, because only a very few programs...

Owing to their strong perpendicular magnetic anisotropy, FePd, CoPd, and their Co(Fe)Pt counterparts are candidate materials for ultrahigh density magnetic recording. The stability and magnetic properties of such films are largely dependent on the orientation and local distribution of the L1(0) FePd phase fraction. Therefore, the formation and tran...

A novel secure data storage architecture based on phase-encoded, thin film, Fourier-type polarization holograms is reported. Efficient data encryption and verification can be obtained by phase modulation of the reference wave introduced by a phase-type spatial light modulator that is imaged onto the hologram plane. A physical model is formulated in...

Polarization holographic read/write and read only demonstrator systems have been developed using ~2 µm thick azobenzene polyester on a card form media. The thin-film holographic system has practical advantages, e.g. high diffraction efficiency, no cross talk between the holograms, reading in reflection mode, no hardware servo, different wavelengths...

Photoinduced anisotropy in azobenzene side-chain polymers are characterized in two ways, by numerical solution of the proper rate-equations and by approximate analytical expression. Feasibility of these methods was investigated by comparison with results of polarization holographic experiments. Agreement with experimental results proves usefulness...

The saturation behavior of diffraction efficiency has been experimentally studied and theoretically modeled in azobenzene polyesters by recording polarization gratings with two beams of orthogonal circular polarization. The model is an extension of the phenomenological expression of Kakichashvili, derived from the rate equations for photoanisotropi...

A response function is derived for the description of photo-induced birefringence and dichroism in case of materials where the underlying process is photo-isomerization. Our result explains the usefulness of the theoretical formulae derived earlier by Kakichashvili for photo-anisotropic materials of another kind, which are widely used in polarizati...

The temporal evolution of photoinduced birefringence is investigated on the basis of a model proposed by Pedersen and co-workers. This model is extended for the case of elliptically polarized light, and used to describe the erasure of photoinduced birefringence by circularly polarized light. It is shown that the anisotropy is not erased, only the d...

Dynamic behavior of thin photoaddressable polyester films was studied. The saturation process due to Fourier holographic recording was investigated. Model experiments show an optimal intensity ratio of the object and reference beams, where the highest efficiency occurs. This ratio is inversely proportional to the reference intensity. The material h...

Dynamic behavior of thin photoaddressable polyester films was studied. The saturation process due to Fourier holographic recording was investigated. Model experiments show an optimal intensity ratio of the object and reference beams, where the highest efficiency occurs. This ratio is inversely proportional to the reference intensity. The material h...

Optical storage properties of thin azobenzene side-chain polyester films were examined by polarization holographic measurements. The new amorphous polyester film is the candidate material for the purpose of rewritable holographic memory system. Temporal formation of anisotropic and topographic gratings was studied in case of films with and without...