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1
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Transmission and Conversion Electron Mössbauer Study of Crystallization of Amorphous FeZrB Alloys

100%
Grabias A., Kopcewicz M.
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vol. 96
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issue 1
123-130
EN
The combined conversion electron emission and γ-transmission Mössbauer spectroscopy are used to investigate the differences in the bulk and surface crystallization of the amorphous FeZrB alloy in which the nanocrystalline bcc-Fe phase was formed due to annealing. The measurements were performed for the ribbons in the as-quenched state, after 1 h annealing at 430-600°C and after short time annealing at 600°C. The clear differences in the surface and bulk crystallization behaviours were detected. Not only the surface crystallization starts at lower annealing temperature than the bulk one, but additional phases were detected at the surface which do not form in the bulk. Structural transformations as a function of annealing time (15-120 s) are compared with those induced by 1 h anneals. The enhanced surface crystallization was attributed to the boron depletion of the surface region which leads to the decrease in the crystallization temperature at the surface.
2
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^{57}Fe Mössbauer Spectroscopy οf Radiation Damaged Allanites

100%
Malczewski D., Grabias A.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1683-1690
EN
Metamict minerals contain radioactive elements that degrade the crystal structure of the minerals. The degradation occurs primarily through progressive overlapping recoil nuclei collision cascades from α-decays of ^{238}U, ^{232}Th, ^{235}U and their daughter products. We report the results of ^{57}Fe Mössbauer spectroscopy, gamma-ray spectrometry and microprobe analysis of three partially metamict allanites, (Ca,Ce,REE)_2(Fe^{2+},Fe^{3+})(Al,Fe^{3+})_2O[Si_2O_7][SiO_4](OH) where REE stands for rare earth elements. The samples were collected in pegmatites from Reno, Nevada (USA), Franklin, New Jersey (USA) and Nya Bastnas Field (Sweden). The absorbed α-dose for these minerals was found to range from 5.8×10^{14} α-decay/mg for the allanite from Reno to 1.9×10^{15} α-decay/mg for the allanite from Franklin. The Mössbauer spectra show a decrease in the Fe^{2+} doublet intensity with increasing absorbed α-dose. We also observe an increase in the line widths of the Fe^{2+} and Fe^{3+} doublets with increasing absorbed α-dose.
3
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Structural Investigation of Rapidly Quenched FeCoPtB Alloys

81%
Grabias A., Latuch J., Oleszak D., Kopcewicz M.
Acta Physica Polonica A
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2011
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vol. 119
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issue 1
68-71
EN
Two sets of Fe_{52-x}Co_{x}Pt_{28}B_{20} (x=0-26 at.%) and Fe_{60-x}Co_{x}Pt_{25}B_{15} (x=0-40 at.%) alloys were prepared in the form of ribbons by the rapid quenching technique. Structure of the samples was characterized by Mössbauer spectroscopy and X-ray diffraction. In the as-quenched alloys the amorphous phase coexisted with the fcc-(Fe,Co)Pt disordered solid solution. Differential scanning calorimetry measurements performed in the range 50-720 °C revealed one or two exothermal peaks. The magnetically hard ordered L1_{0} (Fe,Co)Pt and magnetically soft (Fe,Co)_{2}B nanocrystalline phases were formed due to thermal treatment of the alloys. The influence of Co content on the structure of the as-quenched and heated alloys was studied.
4
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CEMS and RF-Mössbauer Study of Nanocrystalline Fe_{81}Zr_{7}B_{12} Alloy

81%
Kopcewicz M., Grabias A., Nowicki P.
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EN
The combined conversion electron (CEMS) and γ-transmission Mossbauer spectroscopy is used to investigate the differences in the bulk and surface crystallization of the amorphous Fe_{81}Zr_{7}B_{12} alloy. The radio-frequency induced effects (rf collapse and side bands) are used to study the microstructure and magnetic behaviour of the alloy in the amorphous and nanocrystalline states. Rf-Mossbauer experiment permits us to distinguish soft magnetic nanocrystalline bcc-Fe phase from microcrystalline α-Fe.
5
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Mössbauer Study of Magnetic Properties of Fe_{80-x}Co_{x}Zr_7Si_{13} (x = 0-30~at.%) Boron-Free Amorphous Alloys

61%
Kopcewicz M., Grabias A., Latuch J., Ferenc J., Żuberek R., Nesteruk K.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1257-1260
EN
Amorphous Fe_{80-x}Co_{x}Zr_7Si_{13} (x = 0-30 at.%) alloys in which boron was completely replaced by silicon as a glass forming element have been prepared by melt quenching. Partial substitution of iron by cobalt caused the increase of the hyperfine field and saturation magnetization. The specialized rf-Mössbauer measurements revealed that all amorphous alloys studied are magnetically very soft. The rf-sidebands effect, related to magnetostriction, increases with the increase of Co content. In Fe_{50}Co_{30}Zr_7Si_{13} sample the rf field exposure induced partial crystallization of amorphous phase that was attributed to mechanical deformations related to high frequency magnetostrictive vibrations induced by the rf field. The measurements of the hysteresis loop revealed that coercivity increases for higher Co content.
6
Content available remote

Influence of Temperature and Annealing on GMR in Sputtered Permalloy/Cu Multilayers

61%
Urbaniak M., Stobiecki F., Luciński T., Kopcewicz M., Grabias A., Aleksiejew J.
Acta Physica Polonica A
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2000
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vol. 97
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issue 3
539-542
EN
The influence of temperature and annealing on giant magnetoresistance of Si(100)/Cu(20 nm)/Py(2 nm)/(Cu(2 nm)/Py(2 nm))_{100} multilayer (Py = Ni_{83}Fe_{17}) sputtered at room temperature in double face-to-face configuration is reported. It was found that giant magnetoresistance value, ΔR_{GMR}/R_{sat} (where R_{sat} is the resistance in saturation), monotonically decreases with increasing temperature (4.5% at 173 K to about 1% at 373 K). This results from the decrease in magnetic change of resistance, ΔR_{GMR}, and to the lesser extent from an increase in R_{sat}, though both of them are caused by the shortening of electrons mean free path. The observed almost linear decrease in giant magnetoresistance saturation field with increasing temperature is explained by temperature changes of magnetization profile. Vibrating sample magnetometer measurements revealed that the increase in temperature results in pronounced decrease in remnant to saturation magnetization ratio (M_{r}/M_{s}) suggesting that at low temperatures magnetic bridges between Py layers play an important role in magnetization process. It is shown that proper annealing, by an annihilation of bridges and/or lateral decoupling, leads to an increase in giant magnetoresistance ratio from 3.4% in as deposited state to 4.7%.
7
Content available remote

Complex Magnetic Structure of Strongly Coupled Fe/Si Multilayers

61%
Dubowik J., Stobiecki F., Szymański B., Kudryavtsev Y., Grabias A., Kopcewicz M.
Acta Physica Polonica A
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2000
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vol. 97
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issue 3
451-454
EN
Fe/Si multilayers with strong bilinear and biquadratic couplings were investigated. A complex structure revealed by the Mössbauer spectroscopy corresponds to multimode ferromagnetic resonance spectra in a non-saturated state. Simple dispersion relations for antiferromagnetic coupled bilayer structures are shown to be inapplicable to the Fe/Si multilayers with a strong biquadratic component to the antiferromagnetic bilinear coupling.
8
Content available remote

Carbon-Encapsulated Magnetic Nanoparticles Based on Fe, Mn, and Cr for Spintronics Applications

52%
Szczytko J., Osewski P., Bystrzejewski M., Borysiuk J., Grabias A., Huczko A., Lange H., Majhofer A., Twardowski A.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
305-310
EN
We succeeded in the arc-plasma synthesis of carbon-encapsulated Fe, Cr, and Mn-based nanoparticles. The transmission electron microscopy, Mössbauer spectra (of iron) and SQUID magnetometry results demonstrate that the products of the synthesis contain metals and its carbides. The nanoparticles show ferromagnetic or superparamagnetic behavior at high temperatures, which is demanded for nano-spintronics applications.
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