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1
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Spin-Glass Behavior in LaCu₄Mn Compound

100%
Synoradzki K.
Acta Physica Polonica A
|
2017
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vol. 131
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issue 4
1024-1026
EN
The experimental results of the X-ray powder diffraction, magnetic susceptibility, electrical resistivity, and specific heat measurements of the LaCu₄Mn compound are presented. LaCu₄Mn is an intermetallic compound that crystallizes in the hexagonal CaCu₅-type structure (space group P6/mmm, No. 191), where the atoms on the 3g (1/2, 0, 1/2) site create a kagome lattice, which can cause the spin frustration and leads to a variety of interesting states of matter, such as spin-ice, spin-liquid, and spin-glass states. The Rietveld refinement reveals a random distribution of Mn and Cu atoms on the 3g and 2c site, where about 80% of Mn atoms occupy the 3g site. The lattice parameters are a=5.252(1) Å and c=4.176(1) Å. The low-field zero-field-cooled and field-cooled DC magnetic susceptibilities show splitting below the spin freezing temperature T_f ≈33 K. At 2 K the magnetization M(H) exhibits hysteresis with coercivity field of ≈5 kOe. The AC susceptibility measurements exhibit a frequency-dependent cusp, associated with a frequency-dependent freezing temperature. Moreover, there is no clear sign of long range magnetic order in specific heat and resistivity measurements.
2
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Magnetic Properties of CeNi₄Mn_{y}Al_{1-y} Compounds

64%
Synoradzki K., Toliński T.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
210-212
EN
The magnetic properties of the polycrystalline CeNi₄Mn_{y}Al_{1-y} compounds have been investigated combining AC susceptibility, field-cooled and zero-field-cooled DC magnetization and magnetic relaxation measurements. The X-ray diffraction measurements showed that the group CeNi₄Mn_{y}Al_{1-y} is isostructural and crystallizes in the CaCu₅-type structure (P6/mmm). For 0 < y < 1 irreversible magnetism, long-time magnetic relaxation effect and evident upshift of the AC susceptibility peak with increasing frequency are observed at low temperatures. The spin-glass-like behaviour originates from disorder due to the statistical occupation of the 3g site. Using our data we have constructed the tentative phase diagram.
3
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Magnetic Properties of Ce(Cu_{x}Ni_{1-x})_{4}Mn Compounds

64%
Synoradzki K., Toliński T.
|
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vol. 126
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issue 1
300-301
EN
The Ce(Cu_{x}Ni_{1-x})_{4}Mn series of compounds has been studied for a wide range of the x values. The magnetic properties are determined from the temperature dependence of the dc and ac magnetization. A large irreversibility is observed between the zero-field cooled (ZFC) and field-cooled (FC) curves with a maximum in the ZFC one. The ac magnetic susceptibility also shows a peak, which shifts to higher temperatures with increasing frequencies, which is typically observed in spin-glass (SG) systems. The observation of the SG behaviour is further supported by a very slow decay of the isothermal remanent magnetization and by the typical shape of the magnetization curves. A range of x values showing the para-ferromagnetic-SG transitions has been found.
4
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Grain-Size Effect on the Magnetocaloric Properties of the DyCo_{3}B_{2} Compound

64%
Toliński T., Synoradzki K.
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vol. 126
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issue 1
160-161
EN
The compound DyCo_{3}B_{2} has been recently found to show a significant magnetocaloric effect (MCE) at the ferromagnetic ordering temperature T_{C}=22 K. In the present study we verify the influence of the mechanical milling, i.e. the grains size effect on the characteristic parameters describing MCE. The grain size has been determined after each milling time by X-ray diffraction. MCE has been extracted from both the isothermal magnetization and the specific heat measurements. It is found that even a long milling does not spoil significantly the MCE parameters and only t_{m}>5 h reduces noticeably the value of the magnetic susceptibility, the isothermal magnetic entropy change and the relative cooling power.
5
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Specific Heat of the Ce(Ni_{1 - x}Cu_{x})_4Mn Compounds

64%
Synoradzki K., Toliński T.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1079-1081
EN
Specific heat of the Ce(Ni_{1 - x}Cu_{x})_4Mn compounds has been studied. The samples are prepared by induction melting and it is found, based on the X-ray diffraction, that all the compounds keep the CaCu_5-type structure. This series exhibits a transition between the ferromagnetically ordered CeNi_4Mn and the spin-glass CeCu_4Mn compounds, which is well visible in the measurements of the ac susceptibility peak as a function of the magnetic field frequency and in the magnetization relaxation. In the present research we explore the behavior of the specific heat for various x. The changes of the electronic specific heat coefficient γ are determined by analysis of the low temperature part of the C_{p}/T(T^2) dependence. We also observe that the magnetic phase transition is only detectable in the specific heat signal after extraction of the magnetic contribution of the Mn atoms. This is carried out by subtraction of the specific heat of the reference sample.
6
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Magnetoresistance of the CeCo_{1-x}Fe_xGe₃ Alloys

51%
Skokowski P., Synoradzki K., Toliński T.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
1000-1002
EN
A transition from CeCoGe₃ to the CeFeGe₃ compound, i.e. the CeCo_{1-x}Fe_xGe₃ series has been studied by magnetoresistance measurements. Previously, it was reported that at the concentration x ≈ 0.6 the system is in the vicinity of the quantum critical point. In the present research we have performed the isothermal magnetoresistivity investigations (down to 2K) on polycrystalline samples with x = 0.3, 0.4, and 0.6 to gain further insight into the possible existence of quantum critical point in the CeCo_{1-x}Fe_xGe₃ series. Additionally, electrical resistivity as a function of temperature has been measured and analyzed showing features of non-Fermi liquid behavior at low temperatures.
7
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Enhanced Thermoelectric Power Factors in the Ce(Ni_{1-x}Cu_{x})₂Si₂ and CeNi₂(Si_{1-y}Ge_{y})₂ Alloys

51%
Synoradzki K., Toliński T., Koterlyn M.
Acta Physica Polonica A
|
2018
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vol. 133
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issue 3
366-368
EN
In the presence of hybridization of the f states with the conduction electrons Ce-based compounds can show large peaks in the temperature dependence of the Seebeck coefficient, which makes them interesting materials for applications. The Seebeck coefficient and electrical resistivity of the bulk, arc-melted, single phase samples of Ce(Ni_{1-x}Cu_{x})₂Si₂ and CeNi₂(Si_{1-y}Ge_{y})₂ alloys were measured over the temperature range of 2 K to 300 K. All the samples exhibited a positive Seebeck coefficient, which reaches up to ım50μV/K at 150 K and it can be shifted up to 300 K by appropriate doping. The thermoelectric power factor, PF = S²/ρ, reached a maximum of 1.4×10¯³ Wm¯¹K¯² at 290 K and 1.1×10¯³ Wm¯¹K¯² at 110 K for x=0.25 and y=0.75, respectively. For selected representatives of the studied series thermoelectric properties have been measured up to 1000 K.
8
Content available remote

Magnetocaloric Effect in Antiferromagnetic Half-Heusler Alloy DyNiSb

51%
Synoradzki K., Ciesielski K., Kaczorowski D.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
691-693
EN
The low-temperature magnetic, thermal and magnetocaloric properties of the half-Heusler compound DyNiSb were studied on polycrystalline samples. The temperature variations of the magnetization and the heat capacity revealed a phase transition from paramagnetic to antiferromagnetic state at the Néel temperature T_{N} = 3.1 K. The compound exhibits normal and inverse magnetocaloric effect with the isothermal magnetic entropy change reaching 5.2 J/(kg K) at 4.8 K for a magnetic field change of 3 T. The estimated refrigerant capacity is about 58 J/kg.
9
Content available remote

Magnetic Properties and Magnetocaloric Effect of DyNi_{4}Si

45%
Synoradzki K., Kowalski W., Falkowski M., Toliński T., Kowalczyk A.
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vol. 126
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issue 1
162-163
EN
The magnetic properties and magnetocaloric effect (MCE) in DyNi_{4}Si have been studied by the magnetization and specific heat measurements. The saturation magnetic moment in μ_{0}H=9 T is equal to 7.9 μ_{B}/f.u at 4.2 K. A significant MCE has been observed around the second order phase transition at T_{C}=11 K. The maximum magnetic entropy change is -Δ S_{M}=14.5 J kg^{-1}K^{-1} for the magnetic field change of 9 T.
10
Content available remote

Interlayer Exchange Coupling and Proximity Effect in V-Fe Multilayers

45%
Marczyńska A., Synoradzki K., Pugaczowa-Michalska M., Toliński T., Smardz L.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
597-600
EN
We have studied interlayer exchange coupling (IEC) in (110) oriented V/Fe multilayers with ultrathin sublayers up to 7 monolayers (ML). Results showed that IEC energy depends on both vanadium and iron layer thicknesses. The local maxima of the antiferromagnetic coupling were found for V(7 ML)/Fe(4 ML) and V(3 ML)/Fe(3 ML) multilayers (MLs). The strongest AFM coupling energy of about 1.0 mJ/m² was measured at 5 K for the V(7 ML)/Fe(4 ML) multilayer. The position of the AFM peak for V(X ML)/Fe(3 ML) MLs near 3 ML of V spacer was also revealed by ab-initio calculations. Furthermore, theoretical calculations show an induced negative magnetic moment on V atoms near the V-Fe and Fe-V interfaces due to the proximity effect.
11
Content available remote

From Heavy Fermion and Spin-Glass Behavior to Magnetic Order in CeT_4M Compounds

39%
Toliński T., Kowalczyk A., Falkowski M., Synoradzki K., Chełkowska G., Hoser A., Rols S.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1014-1018
EN
We report on the transitions between the ferromagnetic order, spin-glass behavior, heavy fermion and fluctuating valence state in a series of isostructural compounds CeT_4M (T = Ni, Cu; M = Al, Ga, Mn). The dilution of Ce or the T and M elements allowed us to follow the physical properties evolution employing the measurements of the heat capacity, dc magnetic susceptibility, frequency dependent ac magnetic susceptibility, magnetization relaxation, inelastic neutron scattering and also the X-ray photoemission spectroscopy. It is shown that the Mn rich compounds lean towards the spin glass behavior. For the compounds governed by the close to localization Ce 4f states the effect of the crystal electric field has been studied. It has been shown that the spin glass-like behavior can significantly influence the physics of the CeT_4M compounds.
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