TY  - JOUR
AU  - Kasiuk, Julia
AU  - Fedotova, Julia
AU  - Przewoznik, Janusz
AU  - Kapusta, Czeslaw
AU  - Sikora, Marcin
AU  - Zukrowski, Jan
AU  - Grce, Ana
AU  - Milosavljević, Momir
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/962
AB  - Results of the study of oxidised (FeCoZr)(x)(CaF2)(100) (- x) films in a wide composition range (30 LT = x LT = 74 at.%) sintered at oxygen pressures P-O = 43 and 9.8 mPa with X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), Fe-57 Mossbauer spectroscopy (MS), and vibrating sample magnetometry (VSM) are reported. A crystalline metallic core-amorphous oxide shell structure of nanoparticles (NPs) in films oxidised at lower P-O = 43 mPa is observed in TEM images. A combined use of XRD, MS and XAS techniques provides identification of NP phase composition evidencing alpha-FeCo(Zr) core of the variable content depending on x and a complex oxide shell including amorphous alpha-Fe23+O3 together with Co1 - y2+Fey2+O at low x (30-36 at%). Full oxidation of NPs at higher P-O = 9.8 mPa is indicated by TEM, XRD, MS and XAS patterns evidencing the formation of crystalline Co1 - y2+Fey2+O core-amorphous alpha-Fe23+O3 shell structure. Progressive oxidation of NPs with decreasing x at P-O = 4.3 mPa as well as with Po increase is followed by variation of average centre shifts LT delta GT obtained from deconvoluted Fe-57 Mossbauer spectra. Magnetometry measurements of films sintered at P-O = 43 mPa reveal an effect of exchange bias confirming ferromagnetic metallic core-antiferromagnetic oxide shell structure of NPs. The results show that phase composition of oxide shells is governed both by concentration of oxygen available during synthesis and on the x. Schemes of progressive NP oxidation with identified phase composition as a function of P-o and x values are proposed. (C) 2016 Elsevier Inc. All rights reserved.
PB  - Elsevier
T2  - Materials Characterization
T1  - Oxidation controlled phase composition of FeCo(Zr) nanoparticles in CaF2 matrix
VL  - 113
SP  - 71
EP  - 81
DO  - 10.1016/j.matchar.2016.01.010
ER  - 

@article{
author = "Kasiuk, Julia and Fedotova, Julia and Przewoznik, Janusz and Kapusta, Czeslaw and Sikora, Marcin and Zukrowski, Jan and Grce, Ana and Milosavljević, Momir",
year = "2016",
abstract = "Results of the study of oxidised (FeCoZr)(x)(CaF2)(100) (- x) films in a wide composition range (30 LT = x LT = 74 at.%) sintered at oxygen pressures P-O = 43 and 9.8 mPa with X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), Fe-57 Mossbauer spectroscopy (MS), and vibrating sample magnetometry (VSM) are reported. A crystalline metallic core-amorphous oxide shell structure of nanoparticles (NPs) in films oxidised at lower P-O = 43 mPa is observed in TEM images. A combined use of XRD, MS and XAS techniques provides identification of NP phase composition evidencing alpha-FeCo(Zr) core of the variable content depending on x and a complex oxide shell including amorphous alpha-Fe23+O3 together with Co1 - y2+Fey2+O at low x (30-36 at%). Full oxidation of NPs at higher P-O = 9.8 mPa is indicated by TEM, XRD, MS and XAS patterns evidencing the formation of crystalline Co1 - y2+Fey2+O core-amorphous alpha-Fe23+O3 shell structure. Progressive oxidation of NPs with decreasing x at P-O = 4.3 mPa as well as with Po increase is followed by variation of average centre shifts LT delta GT obtained from deconvoluted Fe-57 Mossbauer spectra. Magnetometry measurements of films sintered at P-O = 43 mPa reveal an effect of exchange bias confirming ferromagnetic metallic core-antiferromagnetic oxide shell structure of NPs. The results show that phase composition of oxide shells is governed both by concentration of oxygen available during synthesis and on the x. Schemes of progressive NP oxidation with identified phase composition as a function of P-o and x values are proposed. (C) 2016 Elsevier Inc. All rights reserved.",
publisher = "Elsevier",
journal = "Materials Characterization",
title = "Oxidation controlled phase composition of FeCo(Zr) nanoparticles in CaF2 matrix",
volume = "113",
pages = "71-81",
doi = "10.1016/j.matchar.2016.01.010"
}

Kasiuk, J., Fedotova, J., Przewoznik, J., Kapusta, C., Sikora, M., Zukrowski, J., Grce, A.,& Milosavljević, M.. (2016). Oxidation controlled phase composition of FeCo(Zr) nanoparticles in CaF2 matrix. in Materials Characterization
Elsevier., 113, 71-81.
https://doi.org/10.1016/j.matchar.2016.01.010

Kasiuk J, Fedotova J, Przewoznik J, Kapusta C, Sikora M, Zukrowski J, Grce A, Milosavljević M. Oxidation controlled phase composition of FeCo(Zr) nanoparticles in CaF2 matrix. in Materials Characterization. 2016;113:71-81.
doi:10.1016/j.matchar.2016.01.010 .

Kasiuk, Julia, Fedotova, Julia, Przewoznik, Janusz, Kapusta, Czeslaw, Sikora, Marcin, Zukrowski, Jan, Grce, Ana, Milosavljević, Momir, "Oxidation controlled phase composition of FeCo(Zr) nanoparticles in CaF2 matrix" in Materials Characterization, 113 (2016):71-81,
https://doi.org/10.1016/j.matchar.2016.01.010 . .

TY  - JOUR
AU  - Kasiuk, J. V.
AU  - Fedotova, J. A.
AU  - Przewoznik, J.
AU  - Zukrowski, J.
AU  - Sikora, M.
AU  - Kapusta, Cz
AU  - Grce, Ana
AU  - Milosavljević, Momir
PY  - 2014
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/77
AB  - The relation between nanoscale structure, local atomic order and magnetic properties of (FeCoZr)(x)(CaF2)(100-x) (29 LT = x LT = 73 at. %) granular films is studied as a function of metal/insulator fraction ratio. The films of a thickness of 1-6 mu m were deposited on Al-foils and glass-ceramic substrates, by ion sputtering of targets of different metal/insulator contents. Structural characterization with X-ray and electron diffraction as well as transmission electron microscopy revealed that the films are composed of isolated nanocrystalline bcc alpha-FeCo(Zr) alloy and insulating fcc CaF2 matrix. They grow in a columnar structure, where elongated metallic nanograins are arranged on top of each other within the columns almost normal to the substrate surface. Mossbauer spectroscopy and magnetometry results indicate that their easy magnetization axes are oriented at an angle of 65 degrees-74 degrees to the surface in films with x between 46 and 74, above the electrical percolation threshold, which is attributed to the growth-induced shape anisotropy. Interatomic distances characteristic for metallic state of alpha-FeCo(Zr) nanograins were revealed by X-ray Absorption Spectroscopy. The results show a lack of surface oxidation of the alloy nanograins, so the growth-induced orientation of nanograins in the films cannot be attributed to this effect. The study is among the first to report a growth-induced non-planar magnetic anisotropy in metal/insulator granular films above the percolation threshold and to reveal the origin of it. (C) 2014 AIP Publishing LLC.
T2  - Journal of Applied Physics
T1  - Growth-induced non-planar magnetic anisotropy in FeCoZr-CaF2 nanogranular films: Structural and magnetic characterization
VL  - 116
IS  - 4
DO  - 10.1063/1.4891016
ER  - 

@article{
author = "Kasiuk, J. V. and Fedotova, J. A. and Przewoznik, J. and Zukrowski, J. and Sikora, M. and Kapusta, Cz and Grce, Ana and Milosavljević, Momir",
year = "2014",
abstract = "The relation between nanoscale structure, local atomic order and magnetic properties of (FeCoZr)(x)(CaF2)(100-x) (29 LT = x LT = 73 at. %) granular films is studied as a function of metal/insulator fraction ratio. The films of a thickness of 1-6 mu m were deposited on Al-foils and glass-ceramic substrates, by ion sputtering of targets of different metal/insulator contents. Structural characterization with X-ray and electron diffraction as well as transmission electron microscopy revealed that the films are composed of isolated nanocrystalline bcc alpha-FeCo(Zr) alloy and insulating fcc CaF2 matrix. They grow in a columnar structure, where elongated metallic nanograins are arranged on top of each other within the columns almost normal to the substrate surface. Mossbauer spectroscopy and magnetometry results indicate that their easy magnetization axes are oriented at an angle of 65 degrees-74 degrees to the surface in films with x between 46 and 74, above the electrical percolation threshold, which is attributed to the growth-induced shape anisotropy. Interatomic distances characteristic for metallic state of alpha-FeCo(Zr) nanograins were revealed by X-ray Absorption Spectroscopy. The results show a lack of surface oxidation of the alloy nanograins, so the growth-induced orientation of nanograins in the films cannot be attributed to this effect. The study is among the first to report a growth-induced non-planar magnetic anisotropy in metal/insulator granular films above the percolation threshold and to reveal the origin of it. (C) 2014 AIP Publishing LLC.",
journal = "Journal of Applied Physics",
title = "Growth-induced non-planar magnetic anisotropy in FeCoZr-CaF2 nanogranular films: Structural and magnetic characterization",
volume = "116",
number = "4",
doi = "10.1063/1.4891016"
}

Kasiuk, J. V., Fedotova, J. A., Przewoznik, J., Zukrowski, J., Sikora, M., Kapusta, C., Grce, A.,& Milosavljević, M.. (2014). Growth-induced non-planar magnetic anisotropy in FeCoZr-CaF2 nanogranular films: Structural and magnetic characterization. in Journal of Applied Physics, 116(4).
https://doi.org/10.1063/1.4891016

Kasiuk JV, Fedotova JA, Przewoznik J, Zukrowski J, Sikora M, Kapusta C, Grce A, Milosavljević M. Growth-induced non-planar magnetic anisotropy in FeCoZr-CaF2 nanogranular films: Structural and magnetic characterization. in Journal of Applied Physics. 2014;116(4).
doi:10.1063/1.4891016 .

Kasiuk, J. V., Fedotova, J. A., Przewoznik, J., Zukrowski, J., Sikora, M., Kapusta, Cz, Grce, Ana, Milosavljević, Momir, "Growth-induced non-planar magnetic anisotropy in FeCoZr-CaF2 nanogranular films: Structural and magnetic characterization" in Journal of Applied Physics, 116, no. 4 (2014),
https://doi.org/10.1063/1.4891016 . .

TY  - JOUR
AU  - Fedotova, J. A.
AU  - Przewoznik, J.
AU  - Kapusta, Cz
AU  - Milosavljević, Momir
AU  - Kasiuk, J. V.
AU  - Zukrowski, J.
AU  - Sikora, M.
AU  - Maximenko, A. A.
AU  - Szepietowska, D.
AU  - Homewood, Kevin P.
PY  - 2011
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/4609
AB  - Temperature and magnetic field dependences of electrical conductivity are systematically studied in granular films (Fe45Co45Zr10)(x)(Al2O3)(100-x) (28 LT = x LT = 64) containing crystalline metallic alpha-FeCo-based nanoalloy cores encapsulated in an amorphous oxide shell embedded in an amorphous Al2O3 matrix. Formation of metallic core-oxide shell nanogranules is confirmed by transmission electron microscopy (TEM) and HRTEM. The structure of core and shell is governed with the difference in the oxidation states of Fe and Co ions investigated with EXAFS, XANES and Mossbauer spectroscopy. A considerable negative magnetoresistance (MR) effect of spin-dependent nature is observed in the whole range of x values. Its increase with decreasing temperature is correlated with the magnetic saturation of superparamagnetic metallic nanogranules. The enhanced MR effect in core-shell granular films is related to the percolation of oxide shells and their influence through spin filtering processes. A considerable high field MR at low temperatures and the resulting deviation of MR and squared magnetization are attributed to a magnetic randomness and/or strong magnetic anisotropy of the magnetic oxide shell.
T2  - Journal of Physics. D: Applied Physics
T1  - Magnetoresistance in FeCoZr-Al2O3 nanocomposite films containing metal core-oxide shell nanogranules
VL  - 44
IS  - 49
DO  - 10.1088/0022-3727/44/49/495001
ER  - 

@article{
author = "Fedotova, J. A. and Przewoznik, J. and Kapusta, Cz and Milosavljević, Momir and Kasiuk, J. V. and Zukrowski, J. and Sikora, M. and Maximenko, A. A. and Szepietowska, D. and Homewood, Kevin P.",
year = "2011",
abstract = "Temperature and magnetic field dependences of electrical conductivity are systematically studied in granular films (Fe45Co45Zr10)(x)(Al2O3)(100-x) (28 LT = x LT = 64) containing crystalline metallic alpha-FeCo-based nanoalloy cores encapsulated in an amorphous oxide shell embedded in an amorphous Al2O3 matrix. Formation of metallic core-oxide shell nanogranules is confirmed by transmission electron microscopy (TEM) and HRTEM. The structure of core and shell is governed with the difference in the oxidation states of Fe and Co ions investigated with EXAFS, XANES and Mossbauer spectroscopy. A considerable negative magnetoresistance (MR) effect of spin-dependent nature is observed in the whole range of x values. Its increase with decreasing temperature is correlated with the magnetic saturation of superparamagnetic metallic nanogranules. The enhanced MR effect in core-shell granular films is related to the percolation of oxide shells and their influence through spin filtering processes. A considerable high field MR at low temperatures and the resulting deviation of MR and squared magnetization are attributed to a magnetic randomness and/or strong magnetic anisotropy of the magnetic oxide shell.",
journal = "Journal of Physics. D: Applied Physics",
title = "Magnetoresistance in FeCoZr-Al2O3 nanocomposite films containing metal core-oxide shell nanogranules",
volume = "44",
number = "49",
doi = "10.1088/0022-3727/44/49/495001"
}

Fedotova, J. A., Przewoznik, J., Kapusta, C., Milosavljević, M., Kasiuk, J. V., Zukrowski, J., Sikora, M., Maximenko, A. A., Szepietowska, D.,& Homewood, K. P.. (2011). Magnetoresistance in FeCoZr-Al2O3 nanocomposite films containing metal core-oxide shell nanogranules. in Journal of Physics. D: Applied Physics, 44(49).
https://doi.org/10.1088/0022-3727/44/49/495001

Fedotova JA, Przewoznik J, Kapusta C, Milosavljević M, Kasiuk JV, Zukrowski J, Sikora M, Maximenko AA, Szepietowska D, Homewood KP. Magnetoresistance in FeCoZr-Al2O3 nanocomposite films containing metal core-oxide shell nanogranules. in Journal of Physics. D: Applied Physics. 2011;44(49).
doi:10.1088/0022-3727/44/49/495001 .

Fedotova, J. A., Przewoznik, J., Kapusta, Cz, Milosavljević, Momir, Kasiuk, J. V., Zukrowski, J., Sikora, M., Maximenko, A. A., Szepietowska, D., Homewood, Kevin P., "Magnetoresistance in FeCoZr-Al2O3 nanocomposite films containing metal core-oxide shell nanogranules" in Journal of Physics. D: Applied Physics, 44, no. 49 (2011),
https://doi.org/10.1088/0022-3727/44/49/495001 . .