I. Panagiotopoulos | University of Ioannina/Greece (original) (raw)
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Papers by I. Panagiotopoulos
The Journal of Physical Chemistry A, 2013
Journal of Applied …, Jan 1, 2007
Journal of applied physics, Jan 1, 2006
IEEE Transactions on Magnetics, 1993
SmFeTi, (Sm0.75Tm0.25)FeTi films and Fe/SmFeTi bilayers are prepared by magnetron sputtering on M... more SmFeTi, (Sm0.75Tm0.25)FeTi films and Fe/SmFeTi bilayers are prepared by magnetron sputtering on Mo substrates. Their magnetic properties and the induced anisotropy on the Fe layers are studied by conversion electron Moessbauer spectroscopy and DC magnetization measurements
In mixed valence manganese perovskites the competition between the various types of interactions ... more In mixed valence manganese perovskites the competition between the various types of interactions as double exchange, Jahn-Teller coupling, Coulomb, and antiferromagnetic superexchange which are sensitive to the structural parameters and ...
Physical Review B, 1999
A series of [La2/3Ca1/3MnO3(Lambda/2)/La1/3Ca2/3MnO3(Lambda/2)]15 multilayers, with bilayer thick... more A series of [La2/3Ca1/3MnO3(Lambda/2)/La1/3Ca2/3MnO3(Lambda/2)]15 multilayers, with bilayer thicknesses Lambda between 2 and 32 nm, has been prepared by pulsed laser deposition. The study of their magnetic and magnetotransport properties reveals the presence of an exchange-biasing mechanism at low temperatures. Zero-field-cooling and field-cooling magnetic measurements reveal a blocking temperature around 70 K that is independent from the bilayer thickness, whereas the average film magnetization becomes zero at 250 K. It is observed that the exchange-biasing field HEB at 10 K follows the variation of coercive field Hc with Lambda, indicating that there is a significant contribution in Hc from the exchange anisotropy at the interfaces. The optimum exchange-biasing properties were observed in multilayers with Lambda=8 nm.
Physical Review B, 2001
Compositionally modulated structures consisting of La1-xCaxMnO3 ferromagnetic (FM) layers (x=0.33... more Compositionally modulated structures consisting of La1-xCaxMnO3 ferromagnetic (FM) layers (x=0.33, 0.4, 0.48) and La1-yCayMnO3 antiferromagnetic (AF) layers (y=0.52, 0.67, 0.75) were grown on (001)LaAlO3 by pulsed laser deposition. Thermomagnetic and isothermal magnetic, magnetotransport measurements reveal an exchange biasing mechanism below a blocking temperature TB~70 K. Between 5 K and TB, the observed exponential thermal decay of coercive (Hc) and exchange
MRS Proceedings, 2008
... 22. YY Zou et al., IEEE Trans. Magn. 39, 1930 (2003). 23. J.-U. Thiele, S. Maat, EE Fullerton... more ... 22. YY Zou et al., IEEE Trans. Magn. 39, 1930 (2003). 23. J.-U. Thiele, S. Maat, EE Fullerton, Appl. Phys. Lett. 82, 2859 (2005). 24. M. Alex et al., IEEE Trans. Magn. 37, 1244 (2001). 25. D. Suess, J. Magn. Magn. Mater. 308, 183 (2007). 26. ...
Physical Review B, 1999
La2/3Ca1/3MnO3 doped with Fe were studied by Mössbauer spectroscopy and neutron powder diffractio... more La2/3Ca1/3MnO3 doped with Fe were studied by Mössbauer spectroscopy and neutron powder diffraction. The Mössbauer spectra (MS) reveal that Fe substitutes for Mn as Fe3+ (S=5/2) and is antiferromagnetically coupled to the Mn host lattice. The magnetic behavior, from the neutron diffraction data, is that of a typical 3D Heisenberg ferromagnet. The temperature evolution of the MS differs from that
Physical Review B, 1993
ABSTRACT
MRS Proceedings, 2010
... Colak 3 , Costas Hadjipanayis 4 , Hui Mao 5 , Georgios Diamantopoulos 1 , Michael Fardis 1 , ... more ... Colak 3 , Costas Hadjipanayis 4 , Hui Mao 5 , Georgios Diamantopoulos 1 , Michael Fardis 1 , Georgios ... environmentally friendly, amphiphillic and biocompatible reagents, with a reducing action giving the opportunity to prepare magnetite (Fe3O4) particles under N2 atmosphere ...
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Nanostructured Films and Coatings, 2000
The Journal of Physical Chemistry C, 2009
The Journal of Physical Chemistry A, 2013
Selective immobilization of proteins in well-defined patterns on substrates has recently attracte... more Selective immobilization of proteins in well-defined patterns on substrates has recently attracted considerable attention as an enabling technology for applications ranging from biosensors and BioMEMS to tissue engineering. In this work, a method is reported for low-cost, large scale and high throughput, selective immobilization of proteins on nanopatterned Si, based on colloidal lithography and plasma processing to define the areas (<300 nm) where proteins are selectively immobilized. A close-packed monolayer of PS microparticles is deposited on oxidized Si and, either after microparticle size reduction or alternatively after metal deposition through the PS close-packed monolayer, is used as etching mask to define SiO2 nanoislands (on Si). C4F8 plasma was used to selectively etch and modify the SiO2 nanoislands while depositing a fluorocarbon layer on the Si surface. The plasma-treated surfaces were chemically characterized in terms of functional group identification through XPS analysis and reaction with specific molecules. Highly selective protein immobilization mainly through physical adsorption on SiO2 nanoislands and not on surrounding Si was observed after C4F8 plasma-induced chemical modification of the substrate. The thickness of the immobilized protein monolayer was estimated by means of AFM image analysis. The method reported herein constitutes a cost-efficient route toward rapid, large surface, and high-density patterning of biomolecules on solid supports that can be easily applied in BioMEMS or microanalytical systems.
Sensors and Actuators A: Physical, 2003
It is well known that compounds with high magnetostriction usually exhibit a strong magnetocrysta... more It is well known that compounds with high magnetostriction usually exhibit a strong magnetocrystalline anisotropy, for example, the rare earth--transition metal compounds. Effective reduction of such an anisotropy, while keeping the magnetoelastic properties, is usually achieved by alloying rare earths with opposite anisotropy sign (Terfenol) and by fabricating amorphous TbFe-based alloys. We have studied an alternative kind of materials exhibiting high magnetostriction but in low applied magnetic fields. Inhomogeneous multilayered systems consisting of a hard amorphous Tb-Fe phase, alternated with a magnetically soft amorphous Fe-B phase, were grown by dc sputtering. The thickness of the individual layers ranged from 25 to 75 ; Å. Hysteresis loops, measured at room temperature by VSM, were smooth and showed a reduction in coercivity, as compared to the TbFe single films, indicating that in this multilayer structure both hard and soft phases are exchange coupled. The strain along th...
Physical Review B, 2007
A detailed comparative Mössbauer study of La0.67Ca0.33MnO3 and La0.67Sr0.33MnO3 samples doped wit... more A detailed comparative Mössbauer study of La0.67Ca0.33MnO3 and La0.67Sr0.33MnO3 samples doped with 1% Sn is presented. The spectra at 5K can be analyzed by a single ferromagnetic component. However, at higher temperatures two separate ferromagnetic components and a paramagnetic one are required to fit the spectra. The ferromagnetic component with the lower hyperfine field is attributed to clusters of weakened
Physica B: Condensed Matter, 2008
The dependence of the macroscopic properties of the soft layer on the hard-layer magnetization an... more The dependence of the macroscopic properties of the soft layer on the hard-layer magnetization and microstructure in exchange spring bilayers is studied. The exchange bias field experienced by the soft layer varies proportionally with magnetization as well as magnetic hardness of the hard layer. On the other hand, there is an inverse relationship between the coercivity of the soft layer
The Journal of Physical Chemistry A, 2013
Journal of Applied …, Jan 1, 2007
Journal of applied physics, Jan 1, 2006
IEEE Transactions on Magnetics, 1993
SmFeTi, (Sm0.75Tm0.25)FeTi films and Fe/SmFeTi bilayers are prepared by magnetron sputtering on M... more SmFeTi, (Sm0.75Tm0.25)FeTi films and Fe/SmFeTi bilayers are prepared by magnetron sputtering on Mo substrates. Their magnetic properties and the induced anisotropy on the Fe layers are studied by conversion electron Moessbauer spectroscopy and DC magnetization measurements
In mixed valence manganese perovskites the competition between the various types of interactions ... more In mixed valence manganese perovskites the competition between the various types of interactions as double exchange, Jahn-Teller coupling, Coulomb, and antiferromagnetic superexchange which are sensitive to the structural parameters and ...
Physical Review B, 1999
A series of [La2/3Ca1/3MnO3(Lambda/2)/La1/3Ca2/3MnO3(Lambda/2)]15 multilayers, with bilayer thick... more A series of [La2/3Ca1/3MnO3(Lambda/2)/La1/3Ca2/3MnO3(Lambda/2)]15 multilayers, with bilayer thicknesses Lambda between 2 and 32 nm, has been prepared by pulsed laser deposition. The study of their magnetic and magnetotransport properties reveals the presence of an exchange-biasing mechanism at low temperatures. Zero-field-cooling and field-cooling magnetic measurements reveal a blocking temperature around 70 K that is independent from the bilayer thickness, whereas the average film magnetization becomes zero at 250 K. It is observed that the exchange-biasing field HEB at 10 K follows the variation of coercive field Hc with Lambda, indicating that there is a significant contribution in Hc from the exchange anisotropy at the interfaces. The optimum exchange-biasing properties were observed in multilayers with Lambda=8 nm.
Physical Review B, 2001
Compositionally modulated structures consisting of La1-xCaxMnO3 ferromagnetic (FM) layers (x=0.33... more Compositionally modulated structures consisting of La1-xCaxMnO3 ferromagnetic (FM) layers (x=0.33, 0.4, 0.48) and La1-yCayMnO3 antiferromagnetic (AF) layers (y=0.52, 0.67, 0.75) were grown on (001)LaAlO3 by pulsed laser deposition. Thermomagnetic and isothermal magnetic, magnetotransport measurements reveal an exchange biasing mechanism below a blocking temperature TB~70 K. Between 5 K and TB, the observed exponential thermal decay of coercive (Hc) and exchange
MRS Proceedings, 2008
... 22. YY Zou et al., IEEE Trans. Magn. 39, 1930 (2003). 23. J.-U. Thiele, S. Maat, EE Fullerton... more ... 22. YY Zou et al., IEEE Trans. Magn. 39, 1930 (2003). 23. J.-U. Thiele, S. Maat, EE Fullerton, Appl. Phys. Lett. 82, 2859 (2005). 24. M. Alex et al., IEEE Trans. Magn. 37, 1244 (2001). 25. D. Suess, J. Magn. Magn. Mater. 308, 183 (2007). 26. ...
Physical Review B, 1999
La2/3Ca1/3MnO3 doped with Fe were studied by Mössbauer spectroscopy and neutron powder diffractio... more La2/3Ca1/3MnO3 doped with Fe were studied by Mössbauer spectroscopy and neutron powder diffraction. The Mössbauer spectra (MS) reveal that Fe substitutes for Mn as Fe3+ (S=5/2) and is antiferromagnetically coupled to the Mn host lattice. The magnetic behavior, from the neutron diffraction data, is that of a typical 3D Heisenberg ferromagnet. The temperature evolution of the MS differs from that
Physical Review B, 1993
ABSTRACT
MRS Proceedings, 2010
... Colak 3 , Costas Hadjipanayis 4 , Hui Mao 5 , Georgios Diamantopoulos 1 , Michael Fardis 1 , ... more ... Colak 3 , Costas Hadjipanayis 4 , Hui Mao 5 , Georgios Diamantopoulos 1 , Michael Fardis 1 , Georgios ... environmentally friendly, amphiphillic and biocompatible reagents, with a reducing action giving the opportunity to prepare magnetite (Fe3O4) particles under N2 atmosphere ...
Nanostructured Films and Coatings, 2000
The Journal of Physical Chemistry C, 2009
The Journal of Physical Chemistry A, 2013
Selective immobilization of proteins in well-defined patterns on substrates has recently attracte... more Selective immobilization of proteins in well-defined patterns on substrates has recently attracted considerable attention as an enabling technology for applications ranging from biosensors and BioMEMS to tissue engineering. In this work, a method is reported for low-cost, large scale and high throughput, selective immobilization of proteins on nanopatterned Si, based on colloidal lithography and plasma processing to define the areas (<300 nm) where proteins are selectively immobilized. A close-packed monolayer of PS microparticles is deposited on oxidized Si and, either after microparticle size reduction or alternatively after metal deposition through the PS close-packed monolayer, is used as etching mask to define SiO2 nanoislands (on Si). C4F8 plasma was used to selectively etch and modify the SiO2 nanoislands while depositing a fluorocarbon layer on the Si surface. The plasma-treated surfaces were chemically characterized in terms of functional group identification through XPS analysis and reaction with specific molecules. Highly selective protein immobilization mainly through physical adsorption on SiO2 nanoislands and not on surrounding Si was observed after C4F8 plasma-induced chemical modification of the substrate. The thickness of the immobilized protein monolayer was estimated by means of AFM image analysis. The method reported herein constitutes a cost-efficient route toward rapid, large surface, and high-density patterning of biomolecules on solid supports that can be easily applied in BioMEMS or microanalytical systems.
Sensors and Actuators A: Physical, 2003
It is well known that compounds with high magnetostriction usually exhibit a strong magnetocrysta... more It is well known that compounds with high magnetostriction usually exhibit a strong magnetocrystalline anisotropy, for example, the rare earth--transition metal compounds. Effective reduction of such an anisotropy, while keeping the magnetoelastic properties, is usually achieved by alloying rare earths with opposite anisotropy sign (Terfenol) and by fabricating amorphous TbFe-based alloys. We have studied an alternative kind of materials exhibiting high magnetostriction but in low applied magnetic fields. Inhomogeneous multilayered systems consisting of a hard amorphous Tb-Fe phase, alternated with a magnetically soft amorphous Fe-B phase, were grown by dc sputtering. The thickness of the individual layers ranged from 25 to 75 ; Å. Hysteresis loops, measured at room temperature by VSM, were smooth and showed a reduction in coercivity, as compared to the TbFe single films, indicating that in this multilayer structure both hard and soft phases are exchange coupled. The strain along th...
Physical Review B, 2007
A detailed comparative Mössbauer study of La0.67Ca0.33MnO3 and La0.67Sr0.33MnO3 samples doped wit... more A detailed comparative Mössbauer study of La0.67Ca0.33MnO3 and La0.67Sr0.33MnO3 samples doped with 1% Sn is presented. The spectra at 5K can be analyzed by a single ferromagnetic component. However, at higher temperatures two separate ferromagnetic components and a paramagnetic one are required to fit the spectra. The ferromagnetic component with the lower hyperfine field is attributed to clusters of weakened
Physica B: Condensed Matter, 2008
The dependence of the macroscopic properties of the soft layer on the hard-layer magnetization an... more The dependence of the macroscopic properties of the soft layer on the hard-layer magnetization and microstructure in exchange spring bilayers is studied. The exchange bias field experienced by the soft layer varies proportionally with magnetization as well as magnetic hardness of the hard layer. On the other hand, there is an inverse relationship between the coercivity of the soft layer