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1
Content available remote

STM Observations of Ferromagnetic Clusters

100%
Wawro A., Kasuya A.
Acta Physica Polonica A
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1998
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vol. 93
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issue 2
443-448
EN
Co, Fe and Ni clusters of nanometer size, deposited on silicon and graphite (highly oriented pyrolytic graphite), were observed by a scanning tunneling microscope. Deposition as well as the scanning tunneling microscope measurements were carried out in an ultrahigh vacuum system at room temperature. Detailed analysis of Co cluster height was done with the scanning tunneling microscope equipped with a ferromagnetic tip in the magnetic field up to 70 Oe. It is found that bigger clusters (few nanometers in height) exhibit a dependence of their apparent height on applied magnetic field. We propose that such behaviour originates from the ferromagnetic ordering of cluster and associate this effect to spin polarized tunneling.
2
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STM Imaging of Magnetic Dots with Ferromagnetic Tip

100%
Wawro A., Kasuya A.
Acta Physica Polonica A
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2000
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vol. 97
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issue 3
547-550
EN
We report on imaging of isolated, few nanometers in size, magnetic dots (Co, Ni) by the use of a scanning tunneling microscope equipped with a ferromagnetic Co tip in the presence of external magnetic field. The dependence of apparent height of dots as a function of magnetic field takes a hysteresis-like shape. We discuss possible mechanisms of the scanning tunneling microscope tip interactions with dots.
3
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Grazing Incidence X-Ray Reflectivity Study of MBE-Grown Co/Cu Multilayers

81%
Pełka J. B., Baczewski L. T., Wawro A., Domagała J.
Acta Physica Polonica A
|
1997
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vol. 91
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issue 5
859-863
EN
In this work we report preliminary grazing-incidence X-ray reflectometry studies of multilayer structures composed of 3d metals Co and Cu deposited in the ultra-high vacuum molecular beam epitaxy system. The multilayers of different modulation period were deposited on glass substrate directly, or on 3d -metallic buffers of various thicknesses. The experimental specular reflectivity spectra were analyzed by a comparison with a theoretical model calculated from a recursive algorithm based on the Fresnel formula [1, 2]. It enabled us to estimate the structural parameters concerning layer thickness and roughness. The results obtained are correlated with magnetization measurements of the layered structures, as a function of modulation period, buffer type and thickness. A special attention to influence of interfacial roughness on magnetization results is paid.
4
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STM/STS Studies of Self-Organized Growth of Iron Silicide Nanocrystals on Vicinal Si(111) Surface

81%
Wawro A., Suto S., Czajka R., Kasuya A.
Acta Physica Polonica A
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2003
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vol. 104
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issue 3-4
303-319
EN
The evolution of iron silicide structure grown by solid state epitaxy on Si(111) vicinal surface was investigated by scanning tunnelling microscopy. The reactions, which occur on the surface, are compared for two various Fe coverages: 0.33 and 2 monolayers. The annealing at 250˚C does not enable substantial recovery of the surface ordering, deteriorated by Fe deposition at room temperature. The onset of 2×2 surface reconstruction is observed upon annealing at 400˚C. A three-dimensional growth tendency of iron silicide crystallites on a bare Si(111) 7×7 surface was found at 700˚C. In the case of 2 monolayer coverage crystallites nucleate along the edges of substrate terraces forming a regular array of nanometer size dots. Basing on atomically resolved spectroscopic effects and statistical considerations, structure of iron silicide nanocrystallites as well as Schottky-like character of the barrier at the interface between metallic crystallite and semiconducting substrate is deduced.
5
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Stm Observed Surface Structures and Magnetic Properties of MBE-Grown Metallic Thin Films

71%
Kalinowski R., Baczewski L., Wawro A., Meyer C., Raułuszkiewicz J.
Acta Physica Polonica A
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1998
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vol. 93
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issue 2
409-413
EN
Rare-earth epitaxial thin films of Tb and Gd of the thicknesses between 2 nm and 16 nm were deposited by means of molecular beam epitaxy method. The roughness of the rare-earth films measured by scanning tunneling microscopy was found to be in the range of 1-4.5 nm. The influence of the roughness on the dipolar anisotropy and magnetocrystalline surface anisotropy was estimated. The magnetic measurements have shown that the Gd layers deposited on the Y buffer layers had an easy plane anisotropy. However, for 2 nm thick Gd layer deposited on W buffer layer the perpendicular anisotropy was observed. According to the roughness analysis the possible sources of the perpendicular anisotropy in this sample is mainly the magnetoelastic anisotropy, but the presence of the magnetocrystalline surface anisotropy also cannot be neglected.
6
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Preisach Maps of Multilayered Co/Cu Structures

71%
Gutowski M., Gutowska M., Piotrowski K., Baczewski L., Wawro A.
Acta Physica Polonica A
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2000
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vol. 97
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issue 3
467-470
EN
Magnetooptical Kerr effect measurements of room temperature hysteresis loops were taken using sandwich- and multilayer-type specimens and He-Ne laser light. For maximal external field of ~250 Gs the corresponding Kerr angle reached 0.04 deg. The samples were obtained in the Institute of Physics, Polish Academy of Sciences, Warszawa, using MBE method. The structure of samples may be described by a formula: substrate-buffer layer-(xCo/yCu)_{n} -cover layer. Al_{2}O_{3} (two orientations) and MgO were used as substrates, the buffer layer was made of W, Cu or Fe, x=15, 20 or 25 Å, y=7, 8, 9, 10, 11, 12, 13, 14, and 20 Å, n=25 and 30. 50 Å of gold (Au) served as a cover layer. The genetic algorithm was subsequently used as a data processing tool, in order to reconstruct the Preisach map for each hysteresis loop. The diagrams clearly indicate changes of magnetic interactions caused by varying thicknesses of individual magnetic and non-magnetic layers.
7
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Buffer Induced Magnetic Patterning of Ultrathin Co Layer

62%
Wawro A., Petroutchik A., Kurant Z., Baczewski L., Mazalski P., Maziewski A.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
306-308
EN
The possibility of magnetic anisotropy engineering of ultrathin Co films in the scale of several dozen nanometers is investigated by magnetooptical magnetometry. In Au/Co/Au sandwiches the spin reorientation transition from the out-of-plane to the in-plane configuration is observed, when Co layer thickness exceeds 1.9 nm. Molybdenum as the underlayer suppresses the Co thickness range for which the perpendicular magnetization is stable. The application of patterned buffer in the form of Au islands grown on Mo layer for ultrathin Co film gives rise to the array of spatially stable magnetic dots fabrication ca. 100 nm in lateral size with magnetization perpendicular to the film plane surrounded by the area magnetized in the sample plane.
8
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Structure and Magnetism of MBE-Grown Co/Cu Multilayers

62%
Baczewski L. T., Wawro A., Domagała J., Pełka J., Szewczyk A., Nabiałek A.
Acta Physica Polonica A
|
1997
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vol. 91
|
issue 2
315-319
EN
Structural and magnetic properties of Co/Cu multilayers deposited in the ultra-high vacuum molecular beam epitaxy system on glass substrates with different modulations periods were investigated. A structural characterization was performed by means of RHEED and Auger spectroscopy (in situ), small angle X-ray reflectivity and scanning tunneling microscopy. The samples obtained have a textured, polycrystalline layered structure for deposition at room temperature. Magnetization and in-plane magnetoresistance measurements were performed as a function of Cu and Co layer thicknesses. An influence of different buffers and of interface quality on magnetic properties was investigated.
9
Content available remote

STM/AFM Observations of Co/Cu Magnetic Multilayers

62%
Aleszkiewicz M., Kalinowski R., Czajka R., Polewska W., Wawro A., Baczewski L. T., Raułuszkiewicz J.
Acta Physica Polonica A
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1997
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vol. 91
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issue 2
311-314
EN
UHV deposited magnetic Co/Cu multilayers were investigated by means of scanning tunneling microscopy (STM) and atomic force microscopy (AFM). Surface of the sample i.e. upper covering layer in "plane" configuration and individual sublayers in "cross-section" configuration were investigated. A possibility of structure characterization of metallic multilayers by STM and AFM in the cross-section configuration is demonstrated.
10
Content available remote

Brillouin Light Scattering Investigations οf Magnetic and Elastic Properties in MBE Grown Trilayer Mo/Co/Au Systems

52%
Gieniusz R., Błachowicz T., Maziewski A., Petroutchik A., Baczewski L., Wawro A., Hamrle J., Serga O., Hillebrands B.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
213-216
EN
The magnetic and elastic properties of epitaxially grown Mo/Co/Au trilayer systems were investigated by the Brillouin light scattering and a ferromagnetic resonance. Using both experimental methods the perpendicular uniaxial anisotropy and the effective in-plane twofold anisotropy contributions were determined as the function of the cobalt thicknesses. Acoustic phonons analysis shows that the elastic constants are decreased with increasing cobalt layer thicknesses.
11
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THz Time Domain Spectroscopy of Thin Gold Layers on GaAs

52%
Szczytko J., Adomavicius R., Papis E., Barańska A., Wawro A., Krotkus A., Piętka B., Łusakowski J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1118-1120
EN
Thin layers of Au with the thickness of several nanometers were prepared on a semi-insulating GaAs substrate. The layers' thickness was determined by ellipsometry. THz time-domain spectroscopy was applied to determine a complex index of refraction of thin Au layers. The obtained results allow for a more precise modeling of the performance of semiconductor devices at THz frequencies.
12
Content available remote

Magnetic and Structural Study of (ZnTe)/Co Core-Shell Nanowires Grown by Molecular Beam Epitaxy

52%
Misiuna P., Dłużewski P., Wojciechowski T., Lewińska S., Ślawska-Waniewska A., Wawro A., Wiater M., Wojtowicz T., Baczewski L.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
517-519
EN
Arrays of crystalline ZnTe nanowires grown by vapor-liquid-solid mechanism were covered with cobalt in a molecular beam epitaxy system. Magnetic and structural characterization of such core/shell nanowires was performed. Using scanning electron microscopy and transmission electron microscopy it was found that the mean shell thickness of cobalt was about 35% of the nominal deposition thickness. Deposited cobalt had a polycrystalline structure covering the ZnTe nanowires evenly along their length. With the increment of temperature during Co deposition the roughness of the nanowire sidewalls increases. Vibrating sample magnetometry measurements revealed that the magnetization easy-axis direction is perpendicular to the long axis of the nanowires, which is in agreement with theoretical predictions. Oxidation of Co shell does not change the anisotropy direction of such structures, however it increases their coercivity. Exchange bias effect at the interface of cobalt and cobalt oxides suggested by some authors is not responsible for such anisotropy orientation.
13
Content available remote

Chemical Reactions and Electronic Functions of Carbon Cluster Arrays Studied by Scanning Tunneling Spectroscopy and High-resolution Electron Energy Loss Spectroscopy

52%
Kasuya A., Hu C., Suto S., Tohji K., Takahashi H., Czajka R., Wawro A., Nishina Y.
Acta Physica Polonica A
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1998
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vol. 93
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issue 2
317-322
EN
Novel nanometer scale structures have been produced by thermal heating or laser irradiation on the surface of single- and multi-layers of C_{60} and C_{84} on Si. These structures were examined by combined measurements of scanning tunneling spectroscopy and high resolution electron energy loss spectroscopy. The results show specific chemical reactions of substrate with carbon clusters having single- and double-bonded network. Covalent bonds are formed in some of these chemical reactions.
14
Content available remote

Structural and Magnetic Properties of MBE Grown (Fe/Pt) (111) Multilayers

42%
Marynowska A., Dynowska E., Lewińska S., Seki T., Takanashi K., Kanak J., Pietruczik A., Aleszkiewicz P., Wawro A., Ślawska-Waniewska A., Baczewski L.
Acta Physica Polonica A
|
2016
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vol. 130
|
issue 6
1363-1370
EN
Series of Al₂O₃(0001)/Pt/(Fe/Pt)ₙ/Pt multilayers with variable number of bilayers n and thicknesses of individual layers were grown using molecular beam epitaxy to investigate influence of buffer layer structure, number of bilayers, and individual layer thickness on their structural and magnetic properties. Both columnar and monocrystalline 10 nm Pt (111) buffer layers were used in the experiment. Structure of Pt buffer layer determined the roughness of Fe/Pt interfaces and consequently magnetic properties of the multilayers. When multilayers were deposited on columnar Pt buffer layer, we observed increase of Fe/Pt interfaces roughness with increasing number of bilayers to values exceeding the nominal Fe/Pt bilayer thickness in the upper part of the sample volume, which resulted in the increment of coercivity in the sample with n=15 determined from hysteresis loops measured for perpendicular orientation of magnetic field. When Fe/Pt multilayers were deposited on monocrystalline Pt buffer layer, Fe/Pt interfaces were smooth regardless the number of bilayers. All samples, despite of the quality of buffer layer, number of bilayers, and individual layer thickness revealed easy magnetisation axis oriented in the sample plane.
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