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1
Content available remote

Structural Investigations and Magnetic Properties of BaFe_{12}O_{19} Crystals

100%
Tudorache F., Popa P., Brinza F., Tascu S.
Acta Physica Polonica A
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2012
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vol. 121
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issue 1
95-97
EN
This work was dedicated to the preparation of a barium hexaferrite using the glass crystallization method. The glass flakes were treated at temperatures ranging between 550C and 750°C. The investigation carried out by X-ray diffraction revealed the phase composition and the mean crystallite size. By means of the scanning electron microscopy, the crystallite shape and average size were established. The electric and magnetic properties were investigated at room temperature by means of a Solartron 1260A impedance/gain phase analyzer and a vibrating sample magnetometer. The optimum heat treatment was established to obtain the maximum coercivity of the barium hexaferrite.
2
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Influence of Nb Addition on Magnetic Properties of the Nanocrystalline (Nd₁₀Fe₆₇B₂₃)_{100-x}Nbₓ (where x = 1, 2, 4) Alloy Ribbons

80%
Szwaja M., Pawlik K., Pawlik P., Gębara P., Michalski B.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
623-625
EN
In the present work the magnetic properties and phase constitution of (Nd₁₀Fe₆₇B₂₃)_{100-x}Nbₓ (where x = 1, 2, 4) alloys in the form of ribbons were investigated. The base alloys were prepared by arc-melting the high purity elements with pre-alloyed Fe-B under an Ar atmosphere. The ribbon samples were obtained by controlled atmosphere melt-spinning technique. In order to generate the nanocrystalline microstructure and hard magnetic properties, samples were annealed at various temperatures (from 923 K to 1023 K) for 5 min. The aim of the present work was to determine the influence of Nb admixture and annealing conditions on the phase constitution and magnetic properties.
3
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Fast Microwave-Assisted Synthesis οf Uniform Magnetic Nanoparticles

80%
Kozakova Z., Bazant P., Machovsky M., Babayan V., Kuritka I.
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issue 5
948-949
EN
In recent time, magnetic nanoparticles have become widely used for preparation of advanced magnetic materials and also for biomedical applications. Requirement for preparation of particles of suitable shape and size has appeared, hence, various methods have been developed. Here we present rapid and energy saving one-pot solvothermal synthesis using microwave pressurized system. This method allows tuning the size of the particles as well as their magnetic properties. Spherical Fe_3O_4 nanoparticles are obtained in 30 min; they are uniform with average dimensions of 200 nm and exhibit ferromagnetic behavior dependent on synthesis temperature.
4
Content available remote

Study of the Physical Properties of Cobalt/ Cobalt Oxide Particles Synthesized by Pulsed Laser Ablation in Different Liquid Media

80%
Borghei S., Bakhtiyari F.
Acta Physica Polonica A
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2017
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vol. 131
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issue 3
332-335
EN
This work is devoted to the production of microparticles via pulsed laser ablation from a solid cobalt target immersed in three different solutions of distilled water as well as in ethanol and in acetone, to study the effect of liquid media on the physical properties and structure of particles. The samples were characterized using XRD, SEM and particle size analysis. More than simply Co particles have resulted in each three liquid media, CoO particles were produced only in acetone, whereas Co₃O₄ particles were predominantly produced in water and ethanol.
5
Content available remote

Synthesis and Properties of Mesoporous Maghemite

80%
Kotsyubynsky V., Hrubiak A., Moklyak V., Mohnatska L., Fedorchenko S.
Acta Physica Polonica A
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2018
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vol. 133
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issue 4
1035-1037
EN
Mesoporous maghemite (γ -Fe₂O₃), obtained by thermal decomposition of iron citrate xerogel hydrate, was investigated by X-ray diffraction, scanning electron microscopy, the Mössbauer and impedance spectroscopies and low temperature nitrogen adsorption. The influence of precursor molar concentration on the material morphology, crystalline and magnetic microstructures and electric conductivity was studied. Obtained results open up the possibility for synthesis of ultrafine γ -Fe₂O₃ with controlled structural and morphological characteristics.
6
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Preparation and Investigations of Ni_{0.2}Zn_{0.8}Fe₂O₄ Ferrite Nanofiber Membranes by Needleless Electrospinning Method

80%
Streckova M., Mudra E., Sebek M., Sopcak T., Dusza J., Kovac J.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
729-731
EN
The preparation of Ni_{0.2}Zn_{0.8}Fe₂O₄ nanofiber membranes by simple and versatile needleless electrospinning technique is presented. The single phase of spinel ferrite membrane was obtained after conventional thermal treatment of polyvinyl alcohol (PVA)/metal nitrate precursors at 800°C for 4 h in air. The formation of single-phase fibers was characterized using differential scanning calorimetry accompanied with thermogravimetric analysis. The surface morphology, microstructure and crystal structure were investigated by scanning electron microscopy, X-ray diffraction and transmission electron microscopy. The magnetic properties of the fibrous samples measured in the temperature range from 2 to 300 K verify a soft magnetic behavior, which is quite typical for ferrimagnetic spinel-type ferrites.
7
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Magnetization Reversal Processes in Nanocrystalline (Pr, Dy)-(Fe, Co)-B Bulk Alloys

80%
Przybył A., Pawlik K., Pawlik P., Gębara P., Wysłocki J.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
579-581
EN
The aim of this paper was to study the phase constitution, magnetic properties and magnetization reversal processes in the rapidly solidified bulk (Pr,Dy)-(Fe,Co)-B alloys doped with Zr, Ti, Mn and Ni. The 3 mm outer diameter tubes samples of the Pr₈Dy₁Fe₆₀Co₇Ni_{(6x)}MnₓB₁₄Zr₁Ti₃ (where x = 0, 3, 6) alloys were produced by suction-casting technique. The admixture of Zr was introduced in order to improve their glass forming abilities while Dy was substituted to enhance the magnetocrystalline anisotropy of hard magnetic phase. The effect of Ni and Mn addition on the phase constitution and magnetic properties was studied in the presented work.
8
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Influence of Zn on Structure and Magnetic Properties of Rapid Quenched (Fe-Zn)-Cu-Nb-Si-B Alloys

80%
Kolesar V., Michalik S., Kovac J., Girman V., Sovak P., Kollar P.
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issue 5
790-791
EN
The aim of this work was to study the influence of Zn on the formation of nanostructure in Fe_{73.5 - x}Zn_xCu_1Nb_3Si_{13.5}B_9 (x = 1, 3, 5) ribbons prepared by the melt-spinning technique. X-ray diffraction measurements proved amorphous state of the sample with x = 1. The sample with x = 3 contains a small fraction of Fe_3Si phase and the sample with x = 5 is in nanocrystalline state with the average grain size of about 25 nm. The reduced radial distribution function G(r) was calculated for local structure investigation. Increasing Zn content enhances crystallization during solidification which leads to increase of magnetocrystalline anisotropy and consequently to increase of coercivity.
9
Content available remote

High-Coercivity FePt Nanoparticle Assemblies Embedded in Oxide-Matrix by Atomic Layer Deposition

80%
Kong J., Li A., Gao M., Yan Q., Wu D.
Acta Physica Polonica A
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2013
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vol. 123
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issue 2
173-176
EN
Self-assembled face-centered cubic FePt nanoparticles were embedded into the oxide capping layer using the atomic layer deposition technology. The effect of the oxide-matrix layer on the structure, mono-dispersibility, and magnetic properties of the FePt/oxide composite thin films was investigated. Experimental results suggest that the protection of the oxide-matrix capping layer can effectively inhibit the grain growth and particle aggregation, and preserve the ordered domains of the FePt nanoparticles during the L 1_0 ordering transition through annealing. The combination of the atomic layer deposition capping layer and self-assembled FePt nanoparticles provides a new potential approach to fabricate the ultrahigh-density magnetic recording media.
10
Content available remote

Fe₂O₃ and Gd₂O₃ Nanoparticles Embedded in Mesoporous Silica: Magnetic Properties Comparison

70%
Kapusta O., Zeleňáková A., Hrubovčák P., Girman V., Zeleňák V.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
860-862
EN
Nanocomposite materials containing Fe₂O₃ and Gd₂O₃ nanoparticles with the same concentration were prepared by nanocasting method. At this procedure silica matrix serves as nanoreactor for growth of nanoparticles. Temperature and external dc field dependences of the magnetization both samples were compared. Composite containing Fe₂O₃ nanoparticles shows superparamagnetic behaviour with blocking temperature around 45 K. Otherwise, paramagnetic properties were observed for the sample with Gd₂O₃ (above 10 K). Additionally, due to free pores the silica matrix could serve as medium to increase the number of bonded water molecules. These properties together with appropriate magnetic characteristics make studied materials suitable for magnetic resonance imaging applications.
11
Content available remote

Magnetic Hardening Induced in RCo₅ (R = Y, Gd, Sm) by Short HEBM

70%
Łopadczak P., Bajorek A., Prusik K., Zubko M., Chełkowska G.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
688-690
EN
The paper is focused on the magnetic and structural properties of RCo₅ (R = Y, Gd, Sm) intermetallics fabricated by high energy ball - milling (HEBM). The investigated samples were first produced by arc-melting as bulk materials and then were milled for 1h in dimethylformamide with balls to powder ratio 10:1. The influence of the HEBM parameters on the microstructure was investigated by a variety of complementary measurement methods. The Rietveld refinement was performed to estimate the dependence of crystallite size and microstrain on type of sample. The hysteresis loops were recorded by SQUID magnetometer at 2 K and 300 K and at magnetic field up to μ₀H=7 T. The impact of short HEBM process is visible as the enhancement of coercivity and simultaneous reduction of the saturation magnetization.
12
Content available remote

Preparation and Magnetic Characteristics of Co_{1-δ}Zn_{δ}Fe₂O₄ Ferrite Nanopowders

70%
Kubisztal M., Herok I., Karolus M., Prusik K., Haneczok G.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1236-1239
EN
In the present paper the Co_{1-δ}Zn_{δ}Fe₂O₄ (0 ≤ δ ≤ 1) ferrite nanopowders with a spinel type structure were synthesized using a chemical co-precipitation technique with constant flow rate ν _{FR}=120 cm³/min at three different reaction temperatures i.e. T_r =50°C, 70°C and 90°C. Magnetic and structural characteristics of the obtained materials were investigated by means of X-ray diffraction method, transmission electron microscopy and vibrating sample magnetometer. In the course of studies hysteresis loops M(μ₀H) and the relations of magnetization M_{7T} (determined at μ_0H=7 T), squareness ratio S and the Néel temperature T_{N} versus Zn content were determined and discussed in detail. It was shown that for δ<0.6 the increase in reaction temperature T_r results in a significant increase of the measured magnetic characteristics. In particular, in the case of Co_{0.8}Zn_{0.2}Fe₂O₄ ferrite nanopowder magnetization M_{7T} reaches maximal value of about 80 emu/g.
13
Content available remote

MBE Growth of CdTe/ZnTe Quantum Dots with Single Mn Ions

61%
Gietka K., Kobak J., Rousset J., Janik E., Słupiński T., Kossacki P., Golnik A., Pacuski W.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1056-1058
EN
We report MBE growth and properties of samples with self assembled quantum dots with single manganese ions and low density of quantum dots. Manganese concentration was calibrated using magneto-reflectivity measurements and the giant Zeeman effect in (Cd,Mn)Te and (Zn,Mn)Te layers. Successful incorporation of Mn in the CdTe/ZnTe quantum dots was confirmed using micro-photoluminescence measurements: single manganese ion in quantum dot manifests in sixfold splitting of exciton emission lines due to s, p-d exchange interaction.
14
Content available remote

Phase Analysis of Magnetic Inclusions in Nanomaterials Based on Multiwall Carbon Nanotubes

61%
Brzózka K., Krajewski M., Małolepszy A., Stobiński L., Szumiata T., Górka B., Gawroński M., Wasik D.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
863-865
EN
Functionalized multiwall carbon nanotubes as well as nanocomposite based on that material covered by nanoparticles composed of iron oxides were the subject of investigations. In order to identify all iron-bearing phases including those reported on the base of previous X-ray diffraction measurements, the transmission Mössbauer spectroscopy was utilized. The experiments were carried out both at room temperature and also at low temperatures. It was stated that in the investigated nanotubes some impurities were present, originating from the catalyst remains, in form of Fe-C and α -Fe nanoparticles. The Mössbauer spectra collected for the nanocomposite showed a complex shape characteristic of temperature relaxations. The following subspectra related to iron-based phases were identified: sextet attributed to hematite, with hyperfine magnetic field reduced due to the temperature relaxations, sextet corresponding to iron carbide as well as two doublets linked to superparamagnetic hematite and ferrihydrites.
15
Content available remote

Influence of Cu Layer Thickness on Morphology and Magnetic Properties of Co/Cu Nanowires

61%
Kac M., Kopec M., Cieniek L., Zarzycki A., Kac S., Maximenko A., Dutkiewicz E., Marszalek M.
Acta Physica Polonica A
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2018
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vol. 133
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issue 2
302-305
EN
We studied changes of morphology and magnetic properties of Co/Cu multilayered nanowires, electrodeposited in polycarbonate membranes, as a function of Cu layer thickness. The morphology and structure of wire assemblies with an average diameter of 200 nm and length of 10 μ m, investigated by X-ray diffraction and scanning electron microscopy techniques, revealed polycrystalline structure of Cu and Co layers with smooth lateral surface of nanowires. Overdeposited nanowires created caps which showed flower-like dendrites with shape changing as a function of Cu thickness and electrodeposition parameters. Chemical composition of Co and Cu nanowires analysed by energy dispersive spectroscopy and proton induced X-ray emission showed Cu nanowires free from Co atoms while in Co nanowires, Cu contamination with concentration below 10% was observed. The oxidation traces observed in single-component Cu nanowires did not appear in multilayered nanowires. Magnetic measurements indicated easy axis of magnetization in membrane plane for nanowires with Cu thickness smaller than 20 nm, whereas for larger Cu thicknesses isotropic orientation of magnetization was observed. The presence of Cu atoms in single-component Co nanowires resulted in the appearance of magnetic anisotropy with easy axis along nanowire axis and the increase of coercivity value.
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