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1
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Influence of Transition Metal Substitution on the Low-Field Magnetic Properties in the Gd(Ni_{1-x}T_{x})₃ (T = Fe, Co) Intermetallic Compounds

100%
Bajorek A., Chełkowska G.
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EN
The low-field magnetic properties of polycrystalline Gd(Ni_{1-x}T_{x})₃ (T = Fe, Co) intermetallic compounds are presented. The whole system crystallizes in the rhombohedral PuNi₃ type of crystal structure. The composition dependence of the Curie temperature T_{C}(x) is associated with the change in the number of 3d electrons. Moreover, the field cooled and zero field cooled (FC-ZFC) curves at low applied magnetic field are related to the anisotropy of T element. The saturation magnetic moment M_S(x) upon doping was estimated based on the hysteresis loops M(H).
2
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The Influence of Yb Substitution on the Magnetic, Electric Properties and Electronic Structure οf Yb_{x}Gd_{1-x}Ni_{5} System

100%
Bajorek A., Chełkowska G.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
188-190
EN
The crystal and electronic structure, magnetic and electric properties of intermetallic compounds Yb_{x}Gd_{1-x}Ni_{5} (x = 0.0, 0.2, 0.4, 0.5) are presented. The whole series crystallize in the hexagonal CaCu_{5} type of crystal structure. The ordering temperatures T_{C} and the effective magnetic moments decrease with increase in ytterbium concentration. The electronic structure studied by X-ray photelectron spectroscopy method shows the domination of Ni 3d states nearby the Fermi level. The multiplet structure visible in valence bands is typical of Yb^{3+} ions.
3
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Magneto-History Effect in the Tb_{x}Gd_{1-x}Ni_3 Compounds

81%
Bajorek A., Chełkowska G., Chrobak A., Kwiecień-Grudziecka M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1136-1138
EN
The compounds Tb_{x}Gd_{1-x}Ni_3 with a PuNi_3-type structure have been obtained. The magnetic properties have been investigated by using SQUID magnetometer (Quantum Design MPMS, temperature from 1.9 K to 300 K and magnetic field up to 7 T). The partial replacement of Gd by Tb atoms is reflected in a decrease of the ordering temperature from 115 K (x = 0.0) to 81 K (x=1.0) as well as the increase of the saturation magnetic moment M_{S} from 6.93 μ_{B}/f.u. (x=0.0) to 7.14 μ_{B}/f.u. (x=1.0). A large difference of M(T) curves has been noticed between the so-called field cooling-zero field cooling magnetization. The thermomagnetic curves are sensitive to the applied magnetic field and their origin can be understood as the domain-wall pinning effect and as the temperature dependence of coercivity.
4
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Electrical Resistivity and Electronic Structure of the Tb_{x}Gd_{1-x}Ni_3 System

81%
Chełkowska G., Bajorek A., Chrobak A., Kwiecień-Grudziecka M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1139-1141
EN
In the paper the electric properties and electronic structure of the intermetallic Tb_{x}Gd_{1-x}Ni_3 compounds are presented. The partial replacement of Gd by Tb atoms causes the decrease of the Curie temperature (T_{C}) and the increase of the residual resistivity. According to the Matthiessen rule the scattering mechanisms in ρ(T) have been analyzed. Moreover, the reduced form of the electrical resistivity ρ_{Z} (T - T_{0}) indicates a deviation from the linearity for x > 0.2. This kind of behaviour can be attributed to density of d states near by the Fermi level (E_{F}) which are dominated by Ni 3d states. The valence band spectra as well as the core level lines have been analyzed as the influence of Tb/Gd substitution on the electronic structure.
5
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Effect of Tb/Gd Substitution on Crystal Structure and Exchange Interactions of Gd_{1 - x}Tb_{x}Ni_3 Intermetallic Compounds

81%
Chrobak A., Bajorek A., Chełkowska G.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1132-1135
EN
In the paper an influence of Tb/Gd substitution on crystal structure and exchange interactions of Gd_{1 - x}Tb_{x}Ni_3 (x = 0.0, 0.5, 0.8, 1.0) polycrystalline compounds have been studied. The crystal structure of all samples was checked at the room temperature by means of X-ray diffraction. Exchange integrals of R-R (J_{RR}), T-T (J_{TT}) and R-T (J_{RT}) atoms were evaluated from M(T) magnetization curves (2-300 K, 2 T) based on the mean field theory calculation. As it was shown the samples examined are single phase and crystallize in the PuNi_3 (space group R-3m) type of crystal structure. The Tb/Gd substitution causes the decrease of lattice parameters as well as the volume of the unit cell. With increase of the x parameter the magnetic moment of Tb atoms increases from 6.94 μ_{B} (x = 0.5) to 8.12 μ_{B} (x = 1). The M(T) dependence of the examined compounds depends almost 8 times stronger on exchange interactions within the R-R site than the interactions between the two antiferromagnetically coupled magnetic sublattices R-T.
6
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Effect of Alloying on Magnetism and Electronic Structure of Gd(In_{1-x}Snₓ)₃ System - ab initio Study

81%
Deniszczyk J., Bajorek A., Chełkowska G., Zipper E.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
427-429
EN
We present the results of ab initio study of electronic and magnetic properties of Gd(In_{1-x}Snₓ)₃ alloys carried out with the use of FP-LAPW method. Our precise ab initio calculations for the first time uniquelly confirmed experimentally based predictions that the ground state magnetic structure of the alloys is antiferromagnetic and that upon the In/Sn substitution the magnetic structure undergo transition, changing the antiferromagnetic ordering from the (π00)-type for the GdSn₃ compound to the (ππ0)-type for the GdIn₃ one. Moreover, calculations gave an explanation of the oscillatory variation of density of states at Fermi level indicated by XPS measurements.
7
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Magnetic Properties of Tb(Ni_{1-x}Fe_{x})_{3} (x=0.2, 0.6) Crystalline Compounds and Powders

71%
Ociepka K., Bajorek A., Chrobak A., Chełkowska G., Prusik K.
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vol. 126
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issue 1
180-181
EN
In the paper we present and discuss magnetic properties of the Tb(Ni_{1-x}Fe_{x})_{3} (x=0.2, 0.6) crystalline compounds and their ball-milled powders. The investigated samples are polycrystalline and crystallize in the rhombohedral PuNi_{3} type of crystal structure. The Curie temperature of the material seems to be independent of particle size and is constant. The coercivity depends on the amount of iron dopant. The saturation magnetization decreases after mechanical grinding which is connected with the reduction in particle size. After 6 h milling time the SEM results show the presence of nanoflakes with thickness up to 100 nm or even smaller. Moreover, the pulverization leads to the observed decrease of magnetocaloric effect.
8
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Content available

Corrosion Properties of Ca65–xMg17.5Zn17.5+x (x = 0, 2.5, 5) Alloys

71%
Babilas R., Wojciechowski P., Bajorek A., Sakiewicz P., Cesarz-Andraczke K.
Archives of Metallurgy and Materials
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2019
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vol. 64
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issue 3
9
Content available remote

The Electronic and Magnetic Properties οf Yb_xGd_{1-x}Ni_5 Systems

71%
Szajek A., Werwiński M., Chełkowska G., Bajorek A., Chrobak A.
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issue 5
905-906
EN
The intermetallic compounds Yb_{x}Gd_{1 - x}Ni_5 crystallize in the hexagonal CaCu_5-type structure. Based on wide ranging SQUID-type magnetometer, it was shown that the saturation magnetization decreases with growing concentration of ytterbium. The opposite tendency was observed for the Sommerfeld coefficient obtained in the heat capacity measurements. These results are confirmed using ab initio band structure calculations.
10
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Magnetic Hardening Induced in RCo₅ (R = Y, Gd, Sm) by Short HEBM

71%
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.
11
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Electronic Structure and X-Ray Photoemission Spectra of MPtSn ( rm M = Ti, Zr, Hf)

71%
Morkowski J., Szajek A., Chełkowska G., Bajorek A., Troć R.
Acta Physica Polonica A
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2009
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vol. 115
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issue 5
935-940
EN
The electronic structures of the half-Heusler isostructural compounds TiPtSn, ZrPtSn and HfPtSn were calculated and measured applying the X-ray photoemission spectroscopy. The (Ti, Zr, Hf)PtSn compounds have gaps between the occupied valence band and the empty conduction band, calculated as about 0.75, 1.12, and 1.09 eV, respectively. The calculations were done by the full-potential local orbitals method in the framework of the local spin-density approximation and partly also by the full-potential linear muffin-tin orbitals method by the LmtART code. Experimental X-ray photoemission spectra were measured using photons of energy of 1486.6 eV. The experimental and calculated spectra match quite well except a small shift in the energy scale.
12
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Influence of Substitution and Milling on Structural and Magnetic Properties of Selected Sm(Ni_{1-x}Co_{x})₃ Compounds

62%
Sikora M., Blachliński D., Ociepka K., Prusik K., Bajorek A., Chełkowska G.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
486-488
EN
The influence of substitution of Co for Ni in Sm(Ni_{1-x}Co_{x})₃, where x=0.0, 0,1, 0.2, on the structural and magnetic properties has been investigated. Samples with x= 0.0 and 0.2 were subjected to grinding in a high energy ball mill. The presence of a PuNi₃ type of crystal phase was evidenced for bulk crystalline and powders specimens. With an increase in the cobalt content, an increase at T_{c} was observed. From the magnetic isotherms, the magnetic entropy changes were determined both for solid and powdered samples. It has been shown that the value of the magnetic entropy change at T_c is doubled for the bulk sample with x= 0.2 but it has decreased significantly for all powdered samples.
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