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001-es BibID:BIBFORM123458
035-os BibID:(Scopus)85202058418 (WoS)001296526400001
Első szerző:Gulyás Szilvia (fizikus)
Cím:Structural and phase transformations in Fe-Pd-Ag layered thin films by grain boundary diffusion / Szilvia Gulyás, Gábor L. Katona
Dátum:2024
ISSN:0031-8949
Megjegyzések:The influence of the stacking order and of an additional Ag layer on the formation of ordered phases in thin (<50 nm) layered Fe/Pd and Fe/Ag/Pd films was investigated at 460 C. The samples were prepared by magnetron sputtering at room temperature on Si/SiO2 substrate and were post-annealed in vacuum. Composition depth profiling and X-ray diffraction were used to characterize the processes. It has been shown, that the stacking order strongly influences the formation of ordered phases both in Fe/Pd bilayered and Fe/Ag/Pd trilayered films. In bilayered Fe/Pd films for both stacking orders the FePd3 phase appeared and it also showed L12 ordering for one stacking order. Addition of Ag layer between the Fe and Pd layers found to promote the formation of FePd phase which showed L10 ordering or A1 disordered structure depending on stacking order. Based on the analysis of the chemical depth profiles and XRD patterns the transformations were interpreted by grain-boundary diffusion mechanisms including grain-boundary diffusion induced grain-boundary migration and solid state reaction.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
layered thin film
FePd
FePdAg
multilayer
L10 ordered phase
depth profiling
Megjelenés:Physica Scripta. - 99 : 9 (2024), p. 1-12. -
További szerzők:Katona Gábor (1977-) (fizikus)
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2.

001-es BibID:BIBFORM122562
035-os BibID:(WoS)001258856900001 (Scopus)85196500545
Első szerző:Gulyás Szilvia (fizikus)
Cím:Effect of Mo and W underlayers on ordered phase formation in Fe-Au-Pd multilayer thin films at low temperatures / Szilvia Gulyás, Gábor L. Katona
Dátum:2024
ISSN:2405-8440
Megjegyzések:Fe-Pd based thin films with Au intermediate layer fabricated on different substrates (SiO 2 , SiO 2 /Mo, SiO 2 /W) were investigated at annealing temperatures up to 460 degrees C. The samples were deposited by magnetron sputtering and were post -annealed in vacuum. The ongoing processes were investigated by chemical depth profiling and X-ray diffraction. The experimental results showed that the intermediate Au layer always promoted the formation of FePd 3 phase which also showed L1 2 ordered structure except in one case with W underlayer. However, in the samples with Mo buffer but without the Au interlayer the FePd phase formed and L1 0 ordered phase also appeared for one stacking order. Considering the low diffusivity arising from the annealing temperature the processes were explained by grain boundary diffusion induced reaction layer formation. The formation of the ordered FePd phases was interpreted by the stress accumulation due to the different diffusivity of the components, which relaxes by the shift of the grain boundaries and the transformation of swept over regions. It was concluded, that the effect of the Au interlayer is dominant over the effect of the Mo or W buffer layers.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
fepd
fepdau
buffer layers
l10 ordering
l12 ordering
multilayer
Megjelenés:Heliyon. - 10 : 12 (2024), p. 1-12. -
További szerzők:Katona Gábor (1977-) (fizikus)
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3.

001-es BibID:BIBFORM118616
035-os BibID:(WoS)001179768800001 (Scopus)85183974343
Első szerző:Gulyás Szilvia (fizikus)
Cím:The effect of self-organization during deposition on the segregation behaviour of Au in the Si-Ge-Au nano-multilayer thermoelectric generator system / Szilvia Gulyás, Gábor L. Katona, Gábor Csiszár, János J. Tomán, Csaba Cserháti, Zoltán Erdélyi
Dátum:2024
ISSN:1044-5803
Megjegyzések:Si-Ge-Au amorphous-nanocrystalline composites are important thermoelectric materials where the Seebeck coefficient and the electrical conductivity may be tuned independently. There are many attempts to improve the thermoelectric properties of Si/Ge systems by the addition of additives like Au. However, the effectiveness of doping and the role of Au is not clear. We report on structural transformations and Au segregation behaviour in post-annealed sputter deposited multilayer thin films using composition depth profiling, electron microscopy, xray diffraction and computer simulation. We show that depending on the nominal thickness of the initial Au layers the film volume becomes depleted of Au for thinner Au layers while for thicker Au layers the Au content is much higher in the form of large precipitates. Due to the self-organization and changing of microstructure during deposition the segregation of Au is very different for different Au individual layer thicknesses. In case of thinner Au layers it is enriched at the free surface, while for thicker initial Au layer thickness gold accumulated at the substrate. We have carried out computer simulations based on stochastic kinetic mean-field model. These calculations support the argument that initial Au island size can drastically affect the dissolution/growth and segregation behaviour of gold which can significantly influence the thermoelectric parameters. Based on these results we provide a possible explanation to the difference in thermoelectric properties found in the literature.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
thermoelectric sigeau
nucleation and growth
multilayer thin film
experiments and computer simulations
microstructure dependent segregation of au
au doping
Megjelenés:Materials Characterization. - 209 (2024), p. 1-13. -
További szerzők:Katona Gábor (1977-) (fizikus) Csiszár Gábor (fizikus) Tomán János (1987-) (fizikus) Cserháti Csaba (1963-) (fizikus) Erdélyi Zoltán (1974-) (fizikus)
Pályázati támogatás:TKP2021-NKTA-34
Egyéb
TKP2021-NKTA
Egyéb
2019-2.1.11-TÉT-2019-00061
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4.

001-es BibID:BIBFORM123452
035-os BibID:(Scopus)85088453316
Első szerző:Katona Gábor (fizikus)
Cím:Grain Boundary Diffusion Dominated Mixing and Solid State Reactions in Magnetic Thin Films / Gábor L. Katona, Szilvia Gulyas
Dátum:2020
Megjegyzések:Magnetic thin films with L10 ordered structure usually exhibit high magnetocrystalline anisotropy, reasonable coercivity, saturation magnetization, excellent corrosion resistance. Examples for such systems are Fe-Pt, Co-Pt, Fe-Pd, Fe-Ni. The ordered phases are almost exclusively fabricated by employing high temperature annealing or deposition on heated substrates, because of the activation of the necessary diffusion processes. At lower temperatures bulk diffusion slows down and becomes practically negligible, while diffusion along defects, like grain boundaries and dislocations is still available. During grain boundary interdiffusion the migration of the boundary can happen, and the migrating boundary leaves an alloyed zone behind. This phenomenon is called diffusion induced grain boundary migration (DIGM), and can lead to even full intermixing if the grain size is small enough. Here, after a short introduction of this process, examples of ordered phase formation at low temperatures in magnetic thin films will be reviewed.
ISBN:978-94-024-2034-0
Tárgyszavak:Természettudományok Fizikai tudományok könyvfejezet
könyvrészlet
Grain boundary diffusion
DIGM
Solid state reaction
Magnetic thin film
Ordered phase formation
Megjelenés:Modern Magnetic and Spintronic Materials / eds. Kaidatzis, A., Sidorenko, S., Vladymyrskyi, I., Niarchos, D. - p. 145-162. -
További szerzők:Gulyás Szilvia (1993-) (fizikus)
Pályázati támogatás:GINOP-2.3.2-15-2016-00041
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5.

001-es BibID:BIBFORM086707
035-os BibID:(WoS)000546857500001 (Scopus)85087175252
Első szerző:Kruhlov, Ivan O.
Cím:Structural phase transformations in annealed Pt/Mn/Fe trilayers / I. O. Kruhlov, O. V. Shamis, N. Y. Schmidt, M. V. Karpets, S. Gulyas, E. Hadjixenophontos, A. P. Burmak, S. I. Sidorenko, G. L. Katona, G. Schmitz, M. Albrecht, I. A. Vladymyrskyi
Dátum:2020
ISSN:0953-8984 1361-648X
Megjegyzések:Thermally-activated phase transitions in Pt/Mn/Fe thin films were investigated by a combination of x-ray diffraction, transmission electron microscopy, secondary neutral mass spectrometry depth profiling, atomic force microscopy, and magnetic properties measurements. Post-annealing was carried out in vacuum to different temperatures up to 620 degrees C. Initially, at temperatures between 280 degrees C-450 degrees C first L1(0)-MnPt is formed at the Mn/Pt interface followed by the most likely formation of metastable bcc Fe3Pt, which gets transformed by further annealing to fcc Fe3Pt and eventually to chemically ordered L1(2)-Fe3Pt. The final product after annealing at 620 degrees C consists of two interesting phases, which are relevant for spintronic applications, antiferromagnetic L1(0)-MnPt with addition of Fe and ferromagnetic L1(2)-Fe3Pt, consistent with the initial element composition.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
chemical ordering
solid state reactions
magnetic thin films
Ll0-mnpt
Megjelenés:Journal Of Physics-Condensed Matter. - 32 : 36 (2020), p. 1-9. -
További szerzők:Shamis, O. V. (fizikus) Schmidt, N. Y. Karpets, M. V. Gulyás Szilvia (1993-) (fizikus) Hadjixenophontos, E. Burmak, A. P. Sidorenko, Sergey I. Katona Gábor (1977-) (fizikus) Schmitz, Guido Albrecht, Manfred Vladymyrskyi, Igor A.
Pályázati támogatás:GINOP-2.3.2-15-2016-00041
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6.

001-es BibID:BIBFORM086609
035-os BibID:(WoS)000561800700005 (Scopus)85086412534
Első szerző:Kruhlov, Ivan O.
Cím:Thermally-induced phase transitions in Pt/Tb/Fe trilayers / I. O. Kruhlov, O. V. Shamis, N. Y. Schmidt, S. Gulyas, R. Lawitzki, A. P. Burmak, S. I. Konorev, G. L. Katona, G. Schmitz, M. Albrecht, I. A. Vladymyrskyi
Dátum:2020
ISSN:0040-6090
Megjegyzések:Structural phase formation induced by thermally-activated diffusion processes and intermixing of layered structures is a promising reaction pathway for the synthesis of unexpected (metastable) thin film materials. Furthermore, the sequence of structural phase transitions during annealing can substantially differ from those predicted by corresponding bulk phase diagrams due to the underlying grain boundary diffusion mechanisms as well as surface and interface effects. In this study, phase transitions in Pt/Tb/Fe trilayers occurring during post-annealing up to 620 degrees C were investigated by various techniques including x-ray diffraction, transmission electron microscopy, secondary neutral mass spectrometry, Auger electron spectroscopy depth profiling, and magnetic properties measurements. At an annealing temperature of 215 degrees C pronounced Pt and Tb diffusion intermixing is observed leading to the formation of the binary Pt2Tb phase. Further annealing up to 280 degrees C is accompanied by the appearance of the chemically disordered A1-FePt phase and significant Tb segregation to the outer surface forming an oxide layer. The chemically ordered L(1)0-FePt phase starts to form in parallel to the disappearance of the Pt2Tb phase at 450 degrees C. The final phase product at 620 degrees C is characterized by the coexistence of two remaining phases, L(1)0-FePt and TbO2. Structural phase transitions have a significant impact on the films magnetic properties - heat treatment leads to an enhancement of the coercive field. This fact is associated with the formation of the hard magnetic L(1)0-FePt phase, which might be accompanied by grain isolation induced by partially Tb/Tb-O grain boundary filling.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
diffusion intermixing
solid state reactions
magnetic thin films
terbium
l10-ordered iron-platínum
Megjelenés:Thin Solid Films. - 709 (2020), p. 1-7. -
További szerzők:Shamis, O. V. (fizikus) Schmidt, N. Y. Gulyás Szilvia (1993-) (fizikus) Lawitzki, R. Burmak, A. P. Konorev, S. I. Katona Gábor (1977-) (fizikus) Schmitz, Guido Albrecht, Manfred Vladymyrskyi, Igor A.
Pályázati támogatás:GINOP-2.3.2-15-2016-00041
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7.

001-es BibID:BIBFORM103238
035-os BibID:(WOS)000570817200001 (Scopus)85091078768
Első szerző:Makushko, P. V.
Cím:Formation of ordered L10-FePt phase in FePt-Ag thin films / P. V. Makushko, M. N. Shamis, N. Y. Schmidt, I. E. Kotenko, S. Gulyas, G. L. Katona, T. I. Verbytska, D. L. Beke, M. Albrecht, Iu. M. Makogon
Dátum:2020
ISSN:2190-5509 2190-5517
Megjegyzések:In this work, the influence of an Ag layer, which is located at different positions of the layer stack (top, intermediate, bottom), on the structural and magnetic properties of orderedL1(0)phase in Fe(50)Pt(50)films was investigated. It was found that the position of an additional Ag layer affects the stress state of the as-deposited FePt films. Mechanical stress is induced during deposition and post-annealing process due to the difference in thermal expansion coefficients and lattice mismatch of FePt, Ag, and substrate. The initial stress state affects the ordering process during subsequent heat treatment. The higher level of initial compressive stress (- 7.8 GPa) in FePt/Ag/FePt films results inL1(0)phase formation at a temperature of 700 degrees C which is about 100 degrees C lower than in films with Ag bottom (- 3.6 GPa) and top (+ 0.86 GPa) layers. A more pronounced (001) oriented growth of theL1(0)phase was observed in stacks with Ag top layer as compared to Ag bottom and intermediate layers. The highest values of coercivity were obtained for films with Ag intermediate and bottom layers, which is due to the distribution of Ag along FePt grain boundaries that result in strong exchange decoupling of FePt grains. Furthermore, the formation of the orderedL1(0)phase at comparatively low temperatures of about 370 degrees C was observed in a free-standing FePt/Ag (30 nm)/FePt film.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Stress state
Annealing
Ordering
L1(0)-FePt phase
Coercivity
Megjelenés:Applied Nanoscience. - 10 : 12 (2020), p. 4809-4816. -
További szerzők:Shamis, M. N. Schmidt, N. Y. Kotenko, I. E. Gulyás Szilvia (1993-) (fizikus) Katona Gábor (1977-) (fizikus) Verbytska, T. I. Beke Dezső László (1945-) (fizikus) Albrecht, Manfred Makogon, I. M.
Pályázati támogatás:V4EaP Scholar-ship 51300654
Egyéb
GINOP-2.3.2-15-2016-00041
GINOP
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8.

001-es BibID:BIBFORM079100
035-os BibID:(WoS)000466269900001 (Scopus)85065808233
Első szerző:Shamis, O. V. (fizikus)
Cím:Phase transformations in Pt/Fe bilayers during post annealing probed by resistometry / O. V. Shamis, N. Y. Safonova, M. M. Voron, A. P. Burmak, S. I. Sidorenko, G. L. Katona, S. Gulyas, D. L. Beke, M. Albrecht, I. A. Vladymyrskyi
Dátum:2019
ISSN:0953-8984 1361-648X
Megjegyzések: X-ray diffraction (XRD), secondary neutral mass spectrometry (SNMS) depth profiling, and electrical resistivity measurements were used to follow the phase transformations in Pt/Fe bi-layered thin films during annealing. Initially, the electrical resistivity increases linearly with temperature up to 150 °C due to the contribution of phonon scattering of the metallic Pt and Fe bilayer. Further increase of the annealing temperature leads to a steeper linear increase, which is associated with the initial formation of the chemically disordered A1-phase followed by the formation of the chemically ordered L10-FePt phase, as confirmed by XRD and SNMS studies. Finally, at about 620 °C the single L10-FePt phase has formed throughout the film. Moreover, the electrical resistivity contains also the magnetic contribution to the total resistivity. In this case, the loss in magnetic order is indicated by a change in temperature dependence of the resistivity at about 310 °C, representing the Curie temperature of the initially formed A1-FePt alloy, while the finally formed L10-FePt alloy reveals a higher magnetic transition temperature of about 410 °C. In this study, it has been demonstrated that resistometry in combination with structural and chemical analysis provides valuable information on diffusion processes, structural phase formations and its stability range, as well as on the magnetic transition temperature.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
electrical resistivity
chemical ordering
magnetic thin films
FePt
Megjelenés:Journal Of Physics-Condensed Matter. - 31 : 28 (2019), p. 1-7. -
További szerzők:Safonova, N. Y. Voron, M. M. Burmak, A. P. Sidorenko, Sergey I. Katona Gábor (1977-) (fizikus) Gulyás Szilvia (1993-) (fizikus) Beke Dezső László (1945-) (fizikus) Albrecht, Manfred Vladymyrskyi, Igor A.
Pályázati támogatás:GINOP-2.3.2-15-2016-00041
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