Search results

1

Effect of Al Substitution on the Electronic and Magnetic Properties of GdCo_5

100%

Szajek A., Malinowski W.

Acta Physica Polonica A

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2002

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vol. 101

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issue 4

525-536

EN

Experimental data show that aluminium doped RCo_5 systems crystallize in CaCu_5-type structure for most of the rare-earth elements (R). Al impurities randomly occupy one of the two possible positions (2c and 3g) and there is a critical concentration of Al, x_c=2.0, for RCo_{5-x}Al_x when the Co sublattice becomes nonmagnetic. The ab initio self-consistent calculations show strong dependence of magnetic properties of GdCo_{5-x}Al_x on concentration of Al and position of the impurities in the unit cell, furthermore to fulfil experimental observation of existence of critical concentration, x_c=2.0, the Al impurities should prefer 3g positions otherwise the magnetic moments on Co atoms do not vanish.

2

Crystal-Field Origin of the Giant Magnetocrystalline Anisotropy of PrRu_{2}Si_{2}

100%

Michalski R., Ropka Z., Radwański R.

Acta Physica Polonica A

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2000

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vol. 97

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issue 5

767-770

EN

PrRu_{2}Si_{2} shows ferromagnetism below 14 K with the ordered moment of 2.7μ_{B}. It exhibits an enormous magnetic anisotropy at 4.2 K with the anisotropy field of about 400 T. We have attrributed the magnetism of PrRu_{2}Si_{2} to the Pr^{3+} ions. Thus we performed calculations of the fine electronic structure of the Pr^{3+} ion in the tetragonal symmetry, relevant to PrRu_{2}Si_{2}, taking into account crystal-field and inter-site exchange interactions. Our calculations reproduce well the zero-temperature moment, the single-crystalline magnetization curves, and giant anisotropy field as 400 T. The magnetocrystalline-anisotropy energy K_{1} of 59 J/cm^{3} is the largest known anisotropy - the anisotropy energy of the Nd_{2}Fe_{14}B supermagnet amounts to 12.5 J/cm^{3} only. Unfortunately, this giant anisotropy is confined to low temperatures only which prohibits its technical applications in the permanent-magnet industry.

3

Valence Band and Core Levels of Ce_5Ni_2Si_3 Crystal Studied by X-ray Photoemission Spectroscopy

100%

Toliński T., Kowalczyk A., Chełkowska G., Mihalik M., Timko M.

Acta Physica Polonica A

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2008

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vol. 113

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issue 1

327-330

EN

The crystal of Ce_5Ni_2Si_3 was prepared by the Czochralski method. The X-ray photoemission spectroscopy was measured for the valence band and the core levels. Based on the Ce(3d) doublet and its satellites a small value of the hybridization parameter of the f-states with the conduction electrons Δ=4 meV and the f-occupancy n_f close to 1 were found. X-ray photoemission spectroscopy shows that the region between 0 and 3 eV is predominated by the Ni(3d) and Ce(4f) peaks. Some features of the multiplet structure of the Ce(4f) states are also visible close to the Fermi level.

4

Band Gap Stability in Kondo Insulators

100%

Ślebarski A., Jezierski A., Zygmunt A.

Acta Physica Polonica A

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2000

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vol. 97

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issue 1

59-70

EN

We report on magnetic measurements and electronic structure investigations of CeNiSn and CeRhSb. Both belong to the group of Kondo insulators. The magnetic susceptibility shows the nonmagnetic ground state for these compounds and their alloys. The 3d X-ray photoemission spectroscopy spectra show evidence for the mixed valence state of Ce in CeRhSb alloys, as also seen for CeNiSn, whereas the spectra for the La substituted (Ce,La)NiSn compounds show only evidence for a pure Ce^{3+} ground state. We suggest the presence of Kondo-hole states in (Ce,La)RhSb. The location of the pseudogap in CeRhSb varies with the number of free electron, the valence of Ce, and the f-d hybridization. We discuss the similar crystallographic properties and the closed electronic structures of ZrNiSn-type semi-Heusler alloys and CeNiSn-type Kondo insulators.

5

Magneto-History Effect in the Tb_{x}Gd_{1-x}Ni_3 Compounds

80%

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.

6

Anderson-Kondo Lattice Hamiltonian from the Anderson-Lattice Model: A Modified Schrieffer-Wolff Transformation and the Effective Exchange Interactions

80%

Kądzielawa-Major E., Spałek J.

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vol. 126

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issue 4a

A-100-A-104

EN

We derive the Anderson-Kondo lattice model by applying canonical perturbation expansion for the Anderson-lattice model in direct space. The transformation is carried out up to the fourth order by a modified Schrieffer-Wolff transformation: we separate the part of hybridization term responsible for the high-energy processes (involving the largest in-the-system intraatomic Coulomb interaction between f electrons) and replace it with the virtual processes in higher orders. The higher-order processes lead to three separate exchange interactions. The obtained Hamiltonian contains both the Kondo (f-c) and the superexchange (f-f) interactions, as well as a residual hybridization responsible for the heavy-quasiparticle formation. This effective Hamiltonian can be used to analyze the magnetic or the paired states, as well their coexistence in heavy-fermion systems. The magnitudes of both the Kondo exchange and the superexchange integrals are estimated as a function of bare hybridization magnitude.

7

Band Structure and Magnetic Properties of DO_{3}-Type Fe_{3-x}V_{x}Al Alloys. Super-Cell Approach

80%

Deniszczyk J., Borgieł W.

Acta Physica Polonica A

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2000

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vol. 98

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issue 5

551-554

EN

The electronic structure of Fe_{3-x}V_{x}Al alloys was calculated using the super-cell methodology of alloy modeling. The concentration range of x=0.0÷1.0 was investigated. For a concentration of x=0.0625 the energy based analysis reveals that vanadium prefers to replace the Fe atom at sites with the octahedral coordination. It was found that the iron atoms coordinated by the eight nearest-neighbor Fe atoms preserve their high magnetic moment up to a concentration of x=0.9375 even though the average total magnetic moment goes to zero. The relatively high (≃ -1.0μB) negative magnetic moment of V remains constant up to x≃ 0.5. In the concentration range of x=0.75÷0.9375 the gap at ε_{F} of the minority density of states is observed while the majority density of states displays a sharp peak structure at the Fermi energy. This feature suggests the heavy-fermion behavior of the Fe_{2}VAl compound.

8

Resistivity of (Gd_{1-x}Y_{x})_{2}In Alloys at High Temperatures - Two-Band Model Approach

80%

Borgieł W., Deniszczyk J., Lipowczan M., Braun J.

Acta Physica Polonica A

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2000

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vol. 98

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issue 5

547-550

EN

Two-band model for the substitutionary binary alloy of different rare earth metals with relatively simple 4f multiplet structure placed within the transition metal host matrix was proposed and applied to (Gd_{1-x}Y_{x})_{2}In. The main interaction which causes the magnetic part of the resistivity was assumed in a form of stochastically distributed in space s-f interaction. The calculated high temperature spin disorder resistivity of (Gd_{1-x}Y_{x})_{2}In alloys reproduces well the experimental alloys data.

9

X-Ray Photoemission Spectra of Dy(Co_{1-x}Al_{x})_{2} Systems

80%

Szajek A., Jezierski A., Kowalczyk A., Baszyński J., Bartkowski S., Neumann M., Borstel G.

Acta Physica Polonica A

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1997

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vol. 91

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issue 2

439-442

EN

The electronic structure of Dy(Co_{1-x}Al_{x})_{2} compounds (Laves phase - MgCu_{2}, C15) for Al concentrations x = 0.0, 0.1, 0.2 was investigated by X-ray photoelectron spectroscopy. The results were compared with the ab initio band structure calculations.

10

Valence Band of Ce_2Co_{0.8}Si_{3.2} and Ce_2RhSi_3 Studied by Resonant Photoemission Spectroscopy and FPLO Calculations

80%

Starowicz P., Kurleto R., Goraus J., Walczak Ł., Penc B., Adell J., Szlawska M., Kaczorowski D., Szytuła A.

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vol. 126

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issue 4a

A-144-A-148

EN

This work presents studies of the valence band of two Kondo lattice systems: Ce_2Co_{0.8}Si_{3.2}, which is paramagnetic with the Kondo temperature T_{K} ≈50 K and Ce_2RhSi_3, which is antiferromagnetic below T_{N}=4.5 K and exhibits T_{K} ≈9 K. The photoemission spectra, which are obtained with photon energy tuned to Ce 4d-4f resonance, reveal a Kondo peak at the Fermi energy (E_{F}), its spin-orbit splitting partner at 0.24 eV and a broad maximum related to Ce f^0 final state. The spectra indicate that Kondo peak has a higher intensity for Ce_2Co_{0.8}Si_{3.2}. The off-resonance photoemission data reveal that a maximum in the 3d electron density of states is shifted towards E_{F} for Ce_2Co_{0.8}Si_{3.2} as compared to Ce_2RhSi_3. Full-potential local-orbital calculations were realized with local spin density approach +U approach for 213 stoichiometry. They show that a higher density of states near E_{F} is observed for Ce_2CoSi_3. The calculations also reveal the existing tendencies for antiferromagnetic and ferromagnetic ground states in a case of Ce_2RhSi_3 and Ce_2CoSi_3, respectively.

11

Superconductivity, Magnetism, and Atomic Rattling Phenomena in R_{3}Rh_{4}Ge_{13} (R=Y, Yb, Lu)

80%

Strydom A.

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vol. 126

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issue 1

318-321

EN

We give a first report of the physical properties of the pair of cubic intermetallic compounds R_{3}Rh_{4}Ge_{13}, with R being either Yb or Lu. The crystal structure can be described in terms of 3 atomic cages, and we reveal how certain thermal physical properties are inherent to this particular atomic layout. Close to room temperature, Yb_{3}Rh_{4}Ge_{13} displays strong paramagnetism originating from Yb^{3+} ions, but upon cooling though 100 K the magnetic susceptibility and electrical resistivity behave according to a thermally driven valence instability, and we classify Yb_{3}Rh_{4}Ge_{13} therefore as an intermediate valent f-electron system. Lu_{3}Rh_{4}Ge_{13} behaves in a diamagnetic manner throughout our accessible temperature range, - first with a weakly temperature-dependent magnetic susceptibility below room temperature, and finally with a precipitous drop in the electrical resistivity to zero at 2.5 K when superconductivity sets in.

12

Physical Properties of the (Ga₇₀La₃₀)_2S₃₀₀, (Ga_{69.75}La_{29.75}Er_{0.5})_2 S₃₀₀ Single Crystals

80%

Ivashchenko I., Halyan V., Kevshyn A., Kubatska T., Rosolovska V., Tishchenko P., Olekseyuk I.

Acta Physica Polonica A

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2018

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vol. 133

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issue 4

994-996

EN

Using solution-melt method two single crystals, (Ga₇₀La₃₀)₂S₃₀₀, (Ga_{69.75}La_{29.75}Er_{0.5})₂S₃₀₀, were grown. The maxima of the luminescent radiation in the photoluminescence spectrum of the (Ga_{69.75}La_{29.75}Er_{0.5})₂S₃₀₀ single crystal correspond to the intracentric transitions in the erbium ions: ²H_{11/2}→ ⁴I_{15/2} (525 nm) and ⁴S_{3/2} → ⁴I_{15/2} (545 nm).

13

Phase Composition and Magnetic Properties of the Nanocrystalline Fe_{64.32}Pr_{9.6}B_{22.08}W_{4} Alloy

80%

Filipecka K., Pawlik K., Pawlik P., Wysłocki J., Gębara P., Przybył A.

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vol. 126

|

issue 1

164-165

EN

The aim of the present work was to study the influence of annealing conditions on magnetic properties and the phase constitution of rapidly solidified Fe_{64.32}Pr_{9.6}B_{22.08}W_{4} alloy ribbons. The base alloy was prepared by arc-melting of the high purity elements under an Ar atmosphere. Subsequently the ribbon samples were obtained by melt-spinning technique under low pressure of Ar. In order to develop nanocrystalline structure, the samples were annealed at 1003 K for 5, 10, 20 and 30 min. The room temperature magnetic properties were determined from hysteresis loops measured by VSM magnetometry in the external magnetic field up to 2 T. For comparison the influence of annealing temperature on magnetic properties was studied for the same alloy composition. The ribbons were annealed at temperatures from 929 K to 1023 K for 5 min. X-ray diffractometry was used to determine the phase composition of annealed ribbons. Heat treatment resulted in an evolution of the phase constitution, that caused changes in magnetic properties of the alloy.

14

Effect of Tungsten Addition on Phase Constitution and Magnetic Properties of the Bulk Fe_{65}Pr_{9}B_{26-x}W_x Alloys

80%

Filipecka K., Pawlik P., Pawlik K., Gębara P., Przybył A., Pruba M.

Acta Physica Polonica A

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2015

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vol. 128

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issue 1

104-106

EN

The effect of tungsten addition on phase constitution and magnetic properties of the bulk Fe_{65}Pr_9B_{26-x}W_{x} (where x=2, 4, 6, 8) alloys was studied. The base alloys were prepared by arc-melting of the high purity elements under Ar atmosphere. Samples were produced by suction of an arc-molten alloy to a water-cooled copper mould (the suction-casting method). In order to develop nanocrystalline structure, the samples were subjected to annealing. Heat treatment resulted in an evolution of the phase constitution that caused changes in magnetic properties of the alloys. X-ray diffractometry was used to determine the phase composition of annealed samples. The analysis showed presence of hard magnetic Pr_2Fe_{14}B, paramagnetic Pr_{1+x}Fe_4B_4 and soft ferromagnetic α-Fe phases of annealed samples. The room temperature magnetic properties were determined from hysteresis loops measured by VSM magnetometer in the external magnetic field up to 2 T. The highest hard magnetic parameters were measured for the rod sample of Fe_{65}Pr_9B_{20}W_6 annealed at 1003 K for 5 min.

15

Surface Investigations of Selected Materials by Low-Energy Ion Scattering Technique

80%

Goc-Jagło D., Sitko D., Jagło G., Kim-Ngan N., Soszka W.

Acta Physica Polonica A

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2007

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vol. 111

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issue 5

763-771

EN

Surfaces of three selected materials were investigated by means of low-energy ion-scattering technique: (1) the magnetite (Fe_3O_4) exhibiting the so-called Verwey transition (T_V(bulk)=125 K) accompanied by a small cubic-monoclinic crystal distortion, (2) the intermetallic compound NdMn_2 undergoing an antiferromagnetic-paramagnetic phase transition (T_N=104 K) accompanied by a large crystal distortion with a volume change of 1%, and (3) the typical insulator BaTiO_3 with two structural transitions below 300 K. The primary energy of the (Ne^+, Ar^+) ion beam was in the range of 4-8 keV, and the low-energy ion-scattering spectra were collected in the temperature range of 85-300 K. A large influence from the Verwey transition on the neutralization and re-ionization of scattered ions from magnetite surface was observed, while no visible change at the magnetic phase transition in NdMn_2 was revealed in the low-energy ion-scattering spectra. A strong dependence of the characteristics of the low-energy ion-scattering spectra on the irradiated time was observed for BaTiO_3 indicating that this surface was heavily charged by ion bombardments.

16

Magnetic Behaviour of the Ce-Co-Mn Intermetallics of MgCu₂ Structure Type

80%

Dudric R., Popescu A., Isnard O., Pop V., Coldea M.

Acta Physica Polonica A

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2015

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vol. 128

|

issue 1

67-71

EN

The magnetic properties of CeCoMn, Ce₃Co₃Mn₄ and Ce₃Co₆Mn alloys have been investigated by magnetization and susceptibility measurements in the temperature range (5-300) K and magnetic field up to 12 T. X-ray powder diffraction measurements showed that all three alloys are isostructural and crystallize in the cubic MgCu₂ structure type. Both Ce and Co atoms are non-magnetic in all alloys like in the isostructural compound CeCo₂. Magnetic behavior of the investigated alloys is mostly due to the Mn moments and depends essentially on the Mn-Mn distances. The interaction between the Mn moments is antiferromagnetic in CeCoMn and Ce₃Co₃Mn₄ but a paramagnetic behavior for Ce₃Co₆Mn was evidenced in the studied temperature range.

17

Electronic Structure and Magnetic Properties of La_{1-x}Ce_{x}Pb_3 and La_{1-x}Pr_{x}Pb_3 Alloys

80%

Jezierski A., Kaczkowski J., Cichorek T.

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vol. 125

|

issue 1

111-114

EN

The electronic structure and magnetic properties of La_{1-x}Ce_{x}Pb_3 and La_{1-x}Pr_{x}Pb_3 are studied using the spin-polarized relativistic Korringa-Kohn-Rostoker coherent potential approximation method within the local spin density approximation. The calculated density of states at the Fermi level increases with the increase of the concentration. The dependence of spin and orbital magnetic moments of La_{1-x}Ce_{x}Pb_3 and La_{1-x}Pr_{x}Pb_3 (0 < x < 1) on the concentration is also reported. The densities of states at the Fermi energy are dominated by Ce(Pr) 4f_{5/2} and 4f_{7/2} states.

18

Heat Capacity of Heavy Fermion Compound CeCu_4Ga in High Magnetic Fields

80%

Kowalczyk A., Toliński T., Reiffers M., Zapotoková M., Falkowski M., Gažo E.

Acta Physica Polonica A

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2009

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vol. 115

|

issue 1

123-125

EN

The heat capacity in the applied magnetic field up to 9 T, susceptibility and magnetization of polycrystalline CeCu_{4}Ga are presented. Magnetic ordering was not observed down to 2 K. For temperature T < 200 K a Curie-Weiss behavior is observable giving an effective magnetic moment μ_{eff} =2.53 μ_{B}/f.u. The experimental value of μ_{eff} is close to the calculated one for a free Ce^{3+} ion (μ_{eff} = 2.54 μ_{B}/f.u.), thus indicating the presence of well localized magnetic moments carried by the stable Ce^{3+} ions. At low temperatures the electronic heat capacity coefficient value depends strongly on the temperature range used for the extrapolation and applied magnetic field. We observe a typical heavy fermion behavior with γ value of about 380 mJ mol^{-1} K^{-2} obtained from extrapolation to T = 0 K of the temperature range above 7 K. However, extrapolation of the lowest temperatures range yields the γ value of 3.3 J mol^{-1} K^{-2}.

19

Scattering Processes of Normal and Fluctuating Carriers in ReBa_2Cu_3O_{7-δ} (Re = Y, Ho) Single Crystals with Unidirectional Twin Boundaries

80%

Vovk R., Obolenskii M., Bondarenko A., Goulatis I., Levy M., Chroneos A.

Acta Physica Polonica A

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2007

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vol. 111

|

issue 1

123-128

EN

The effect of twin boundaries on the normal and fluctuating conductivity of ReBaCuO (Re = Y, Ho) single crystals was investigated. The results indicate that the Lawrence-Doniach theoretical model describes adequately the temperature dependence of the excess conductivity. The twin boundaries are efficient scattering centers for normal and fluctuating carriers. The derived values of the coherence length perpendicular to the ab-planeξ_c(0) are in good agreement with those obtained from magnetic measurements for stoichiometric YBaCuO crystals.

20

Heat Capacity Studies of NdNi_4Si Compound

80%

Falkowski M., Reiffers M., Zapotoková M., Kowalczyk A., Toliński T., Gažo E.

Acta Physica Polonica A

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2009

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vol. 115

|

issue 1

126-128

EN

The study of the heat capacity of the intermetallic compound NdNi_{4}Si including the effect of the magnetic field is reported. This compound crystallizes in the hexagonal CaCu_5-type structure, space group P6/mmm. NdNi_{4}Si is ferromagnetic with T_C = 8 K and the saturation magnetic moment of 1.5 μ_{B}/f.u. at 4.2 K (in H = 9 T). The heat capacity was analyzed considering the electronic contribution, the Schottky anomaly, and the lattice contributions in the frames of the Debye model. The scheme of the energy levels created by the crystal electric field split is determined from the Schottky contribution to the specific heat. NdNi_{4}Si was characterized by the electronic heat capacity coefficient γ = 85 mJ/(mol K^2) and the Debye temperature Θp_D = 325 K.

Refine search results

Effect of Al Substitution on the Electronic and Magnetic Properties of GdCo_5

Crystal-Field Origin of the Giant Magnetocrystalline Anisotropy of PrRu_{2}Si_{2}

Valence Band and Core Levels of Ce_5Ni_2Si_3 Crystal Studied by X-ray Photoemission Spectroscopy

Band Gap Stability in Kondo Insulators

Magneto-History Effect in the Tb_{x}Gd_{1-x}Ni_3 Compounds

Anderson-Kondo Lattice Hamiltonian from the Anderson-Lattice Model: A Modified Schrieffer-Wolff Transformation and the Effective Exchange Interactions

Band Structure and Magnetic Properties of DO_{3}-Type Fe_{3-x}V_{x}Al Alloys. Super-Cell Approach

Resistivity of (Gd_{1-x}Y_{x})_{2}In Alloys at High Temperatures - Two-Band Model Approach

X-Ray Photoemission Spectra of Dy(Co_{1-x}Al_{x})_{2} Systems

Valence Band of Ce_2Co_{0.8}Si_{3.2} and Ce_2RhSi_3 Studied by Resonant Photoemission Spectroscopy and FPLO Calculations

Superconductivity, Magnetism, and Atomic Rattling Phenomena in R_{3}Rh_{4}Ge_{13} (R=Y, Yb, Lu)

Physical Properties of the (Ga₇₀La₃₀)_2S₃₀₀, (Ga_{69.75}La_{29.75}Er_{0.5})_2 S₃₀₀ Single Crystals

Phase Composition and Magnetic Properties of the Nanocrystalline Fe_{64.32}Pr_{9.6}B_{22.08}W_{4} Alloy

Effect of Tungsten Addition on Phase Constitution and Magnetic Properties of the Bulk Fe_{65}Pr_{9}B_{26-x}W_x Alloys

Surface Investigations of Selected Materials by Low-Energy Ion Scattering Technique

Magnetic Behaviour of the Ce-Co-Mn Intermetallics of MgCu₂ Structure Type

Electronic Structure and Magnetic Properties of La_{1-x}Ce_{x}Pb_3 and La_{1-x}Pr_{x}Pb_3 Alloys

Heat Capacity of Heavy Fermion Compound CeCu_4Ga in High Magnetic Fields

Scattering Processes of Normal and Fluctuating Carriers in ReBa_2Cu_3O_{7-δ} (Re = Y, Ho) Single Crystals with Unidirectional Twin Boundaries

Heat Capacity Studies of NdNi_4Si Compound