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1
Content available remote

Paramagnetism of Cu_3RE_2W_4O_{18} Semiconductors (RE = Gd, Dy-Er)

100%
Groń T., Tomaszewicz E., Duda H., Mazur S.
Acta Physica Polonica A
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2013
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vol. 124
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issue 5
885-887
EN
Cu_3RE_2W_4O_{18} tungstates (RE = Gd, Dy-Er) are paramagnets in the temperature range 4.2-300 K visible also in the absence of the energy losses in the curve of the imaginary part of magnetic susceptibility, χ". The negative values of the paramagnetic Curie-Weiss temperature, θ, may suggest the weak antiferromagnetic coupling below 4.2 K. The temperature independent component of magnetic susceptibility has a positive value indicating a domination of the Van Vleck contribution. Calculations of the effective number of the Bohr magnetons revealed that the orbital contribution to the magnetic moment comes mainly from the RE^{3+} ions.
2
Content available remote

Electrical Transport Properties of Yb_{8-x}Y_xV_2O₁₇ (x=0,2,8)

88%
Sawicki B., Piz M., Filipek E., Groń T., Duda H.
Acta Physica Polonica A
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2017
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vol. 132
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issue 2
363-366
EN
The UV-vis-NIR and electrical properties of Yb_{8-x}Y_xV_2O₁₇ for x=0, 2, and 8 were investigated. The band energy gap of 2.6 eV determined for Yb_6Y_2V_2O₁₇ (x=2) and comparable for the remaining compounds with x=0 and 8 is characteristic for insulators. Low electrical conductivity with a characteristic minimum shifting to higher temperatures from 322, via 360 to 370 K in the sequence x=0, 2 and 8, which decreases with increasing content of ytterbium was observed. Temperature dependence of thermoelectric power showed n-p transition at 410 and 467 K for x=0 and 2, respectively, and n-type conductivity for x=8, indicating mainly n-type electrical conductivity. A breakdown voltage of 26 V/mm is mainly observed for the I-V characteristics at 400 K and showing a varistor-like behavior.
3
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Ferromagnetic Order in Single-Crystalline (Cd_{x}Al_{y})[Cr_2]Se_{z} Semiconductors

88%
Duda H., Rduch P., Malicka E., Groń T., Kusz J.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
702-704
EN
Measurements of the magnetic properties, the electrical conductivity and the Seebeck effect were performed on single crystals (Cd_{x}Al_{y})[Cr_2]Se_{z} between 77 and 300 K. All samples have a ferromagnetic order with the Curie temperature of 130 K and the paramagnetic Curie-Weiss temperature of 155 K. Both these temperatures do not depend significantly on the Al substitution. The electrical conductivity of single crystals CdCr_2Se_4 doped with Al was p-type and showed the change of log σ versus 1/T slope above 150 K. This fact is interpreted as being due to the onset of impurity conduction and structural defects.
4
Content available remote

Superparamagnetic-Like Behaviour in RE_2WO_6 Tungstates (Where RE = Nd, Sm, Eu, Gd, Dy, Ho and Er)

88%
Groń T., Tomaszewicz E., Urbanowicz P., Duda H., Mydlarz T.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
708-710
EN
The magnetization isotherms were used to study the superparamagnetic-like behaviour in polycrystalline (powder) RE_2WO_6 tungstates (where RE = Nd, Sm, Eu, Gd, Dy, Ho and Er). The magnetization isotherms of the majority tungstates under study revealed both the spontaneous magnetic moments and hysteresis characteristic for the superparamagnetic-like behaviour with blocking temperature T_{B} ≈ 30 K except the Sm_2WO_6 and Eu_2WO_6 compounds.
5
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Hopkinson-Like Effect in Single-Crystalline CdCr_2Se_4 and Cd[Cr_{1.89}Ti_{0.08}]Se_4

88%
Malicka E., Groń T., Pacyna A., Duda H., Krok-Kowalski J.
Acta Physica Polonica A
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2012
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vol. 121
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issue 3
690-693
EN
The static (dc) and dynamic (ac) magnetic measurements of CdCr_2Se_4 and Cd[Cr_{1.89}Ti_{0.08}]Se_4 showed their ferromagnetic properties with a Curie temperature T_{C} ≈ 130 K and revealed on the real component of ac susceptibility curve, the peaks near T_{C} at 200 Oe, 450 Oe and 1 kOe, characteristic for the Hopkinson ones. The meaningful reduction of saturation moment to 4.73 μ_{B}/f.u. for Cd[Cr_{1.89}Ti_{0.08}]Se_4 suggests the diamagnetic configuration of Ti ions, which dilutes the ferromagnetic sublattice of Cr ones and causes reducing of the energy losses visible on the imaginary components of ac susceptibility curve. Close for zero values of higher susceptibility harmonics above T_{C} are pointing out to the lack of the spin fluctuations in the paramagnetic state.
6
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Electrical and Magnetic Characterization οf ZnCr_{2-x}V_{x}Se_{4} Spinel Semiconductors

88%
Duda H., Malicka E., Groń T., Pacyna A., Kusz J.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
962-963
EN
Single crystals of ZnCr_{2}Se_{4} spinel doped with vanadium were prepared by chemical vapour transport. The chemical compositions of three crystals have been determined by X-ray diffraction. The structure refinement using the SHELXL-93 program system determine the cation distribution in the system as ZnCr_{2-x}V_{x}Se_{4}. For x values equal to 0.03, 0.1 and 0.13 the observed symmetry was cubic, space group Fd3m. Based on the structural data, influence of the V ions on the magnetic and electrical properties has been analyzed.
7
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Influence of Temperature on Critical Fields in Zn_{x}Sb_{y}Cr_{z}Se_{4}

88%
Malicka E., Groń T., Duda H., Pacyna A., Krok-Kowalski J.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
964-966
EN
The electrical and complex ac dynamic magnetic susceptibility measurements were used to study an influence of temperature on critical fields in single-crystalline Zn_{x}Sb_{y}Cr_{z}Se_{4} spinel system with y = 0.11, 0.16 and 0.20. The p-type conduction and a shift both of the Néel temperature T_{N} to lower temperatures and a susceptibility peak at T_{m} in the paramagnetic region - to higher temperatures were established. Below T_{N} the magnetic field dependence of susceptibility, χ_{ac}(H), shows two peaks. First peak at the critical field H_{c1} slightly decreases with temperature and remains almost constant as Sb content increases. Second peak at the critical field H_{c2} drops rapidly with temperature and remains almost unchanged as Sb content increases. At T_{N} both critical fields disappear.
8
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Influence of Cr-Substitution on the Electrical Properties of Fe_{1-x}Cr_xVSbO_6

88%
Duda H., Filipek E., Dąbrowska G., Groń T., Mydlarz T.
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EN
Fe_{1-x}Cr_xVSbO_6 solid solution is semiconductor with the activation energy decreasing both in the intrinsic and extrinsic conductivity temperature regions as the Cr-content increases. The n-type conduction is observed for Fe-richer samples while a change of the Seebeck coefficient (from n to p) - for Cr-richer ones. Magnetic isotherms for all samples of solid solution under study are characteristic of the universal Brillouin function, indicating paramagnetic response. These effects are discussed within the framework of the appearance of the mixed valence of both Fe and Cr ions.
9
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Influence of Cr-Substitution on the Electrical Properties of Fe_{1-x}Cr_{x}SnSbO₆

88%
Groń T., Dąbrowska G., Filipek E., Duda H., Sawicki B.
Acta Physica Polonica A
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2016
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vol. 129
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issue 1a
A-153-A-156
EN
Fe_{1-x}Cr_xSnSbO₆ solid solution shows semiconducting behaviour with the activation energy decreasing from E_{A}=0.64 eV for x=0.0 to E_{A}=0.32 eV for x=1.0 in the intrinsic conductivity temperature region as well as the n-type conduction at room temperature. The I-V characteristics and the conductance G at 300 and 400 K showed symmetrical and nonlinear behavior in the voltage range (-100, 100 V) suggesting the electron emission over the potential barrier especially for the boundary compounds FeSnSbO₆ and CrSnSbO₆. These effects are discussed in the context of the energy gap E_{g}>1.6 eV many times greater than the thermal energy kT.
10
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Electrical and Magnetic Studies of the Cd_{x}Cr_{y}V_{z}Se_{4} Spinels

76%
Groń T., Duda H., Malicka E., Zawisza B., Krok-Kowalski J., Pacyna A.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
969-970
EN
The electrical and magnetic investigations carried out on the polycrystalline spinels with the general chemical formula Cd_{x}Cr_{y}V_{z}Se_{4} (where z = 0.06, 0.12, 0.24, and 0.31) revealed semiconducting and ferromagnetic properties with a Curie temperature of 127.5 K. A step-like structure of the electrical conductivity, σ(T), was observed for the polycrystal containing 6% V ions in the octahedral sites while the remaining samples showed a typical Arrhenius behaviour of σ(T). These effects are interpreted in terms of ferromagnetic spin clusters which finally dissolve on going towards the paramagnetic limit including non-stoichiometry.
11
Content available remote

Effect of Cation Substitution on Critical Fields in the n-type Zn_{x}Sn_{y}Cr_{z}Se_{4} Spinel Semiconductors

76%
Groń T., Jendrzejewska I., Maciążek E., Pacyna A., Duda H., Zajdel P., Krok-Kowalski J.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
971-974
EN
The ac dynamic magnetic susceptibility was used to study a cation substitution on critical fields in polycrystalline (Zn_{0.87}Sn_{0.048})Cr_{2.02}Se_{4} and Zn_{0.93}[Cr_{1.95}Sn_{0.05}]Se_{4} spinels with tetra- and octahedral coordination of Sn ions, respectively. An increasing static magnetic field shifts the Néel temperature T_{N} to lower temperatures while a susceptibility peak at T_{m} in the paramagnetic region - to higher temperatures. Below T_{N} the magnetic field dependence of susceptibility, χ_{ac}(H), shows two peaks at critical fields H_{c1} and H_{c2}. The values of H_{c1} decrease slightly with temperature while the values of H_{c2} decrease strongly with temperature, especially for spinel with octahedral coordination of Sn ions, suggesting a weakness of the ferromagnetic component.
12
Content available remote

Mictomagnetic Order in Cd_{0.87}Cr_{1.93}V_{0.06}Se_4 Semiconductor

76%
Groń T., Malicka E., Zawisza B., Duda H., Krok-Kowalski J., Pacyna A.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
714-716
EN
The complex ac dynamic magnetic susceptibility was used to study the mictomagnetic-like behavior in polycrystalline Cd_{0.87}Cr_{1.93}V_{0.06}Se_4 spinel. The temperature dependences of the zero field in-phase (real part) and out-of-phase (imaginary part) components of fundamental susceptibility measured at the oscillating field H_{ac} = 0.5 Oe and at the constant frequency of 125 Hz are characteristic for the mictomagnetic order. These results well correlate with the anomalies in the second and third harmonics of the ac susceptibility indicating the cluster glass.
13
Content available remote

Influence of Cu, Ga and Au Dopants and Technology Conditions on the Magnetic Interactions in HgCr_2Se_4 Single Crystals

76%
Krok-Kowalski J., Władarz G., Groń T., Duda H., Pacyna A., Nikiforov K., Rduch P.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
970-972
EN
For single crystals HgCr_2Se_4 doped by nonmagnetic Cu^{+}, Au^{2+} and Ga^{3+} ions and single crystals of HgCr_2Se_4 matrix growing in different synthesis conditions both the dc and ac magnetic susceptibility as well as the magnetization have been measured. As it follows from the analysis of the obtained results, paradoxically, the dopants strengthen the long range magnetic interactions of the ferromagnetically ordered single crystals under study, evidenced by the higher values of the ordering temperature in comparison with those ones for pure matrix. An influence of the technological processes connected with deficiency and/or excess of Hg on the long range magnetic interactions was not observed.
14
Content available remote

Synthesis and Magnetic Properties of CuCr_{1.65}Se_4 Nanoparticles

76%
Maciążek E., Panek J., Kubisztal M., Karolus M., Groń T., Duda H.
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vol. 126
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issue 5
1137-1139
EN
CuCr_{1.65}Se_{4} nanoparticles crystallize in the monoclinic Cr_{2}Se_{3}-type structure of the space group I2/m. The average crystallite size basing on the line broadening is less than 10 nm. With decrease of the size of grains a change from ferromagnetic to ferrimagnetic order, a lack of the magnetization saturation and a strong spin-orbit coupling visible in the large value of the Landé factor g_{χ} = 2.72 are observed. The change in magnetic order is caused by the change of the crystalline symmetry from the cubic phase to monoclinic one.
15
Content available remote

Semiconducting Properties of Cu_5SbO_6

76%
Groń T., Filipek E., Dąbrowska G., Duda H., Mazur S., Kukuła Z., Pawlus S.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1105-1107
EN
Thermoelectric power, electrical resistivity, I-V characteristics, relative electrical permittivity, dc magnetization and ac magnetic susceptibility measurements carried out on Cu_5SbO_6 showed p-type semiconducting behaviour with the activation energy of 0.24 eV as well as ferrimagnetic order with the Néel temperature of 5.2 K. The effective magnetic moment of 5.857 μ_{B}/f.u. revealed the orbital contribution to the magnetic moment. Large value of the relative electrical permittivity indicated that the Cu^{2+} ions with the unscreened and unfilled electron shells are responsible for the polarizability and forming of electric dipoles.
16
Content available remote

Electrical and Magnetic Studies of Zn_{x}Mn_{y}Cr_{z}Se_{4} p-Type Semiconductors

76%
Jendrzejewska I., Groń T., Duda H., Zajdel P., Pacyna A., Maciążek E.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
913-915
EN
The structural, electrical and magnetic investigations carried out on the Zn_{x}Mn_{y}Cr_{z}Se_{4} polycrystals with y = 0.19, 0.29 and 0.38 revealed the spinel structure with the Mn ions occupying tetrahedral sites, p-type conduction with polaronic transport at high temperatures and antiferromagnetic order with a Néel temperature of 20 K and a Curie-Weiss temperature of 103 K. With increasing Mn content in a sample both the effective magnetic moment and the re-entrant temperature increase while the first and second critical fields connected with a metamagnetic transition and the breakdown of the conical spin arrangement decrease, respectively. These results are interpreted in terms of giant cubic anisotropy as well as an effect of Mn impurities on the screw structure of ZnCr_{2}Se_{4}.
17
Content available remote

Correlation between the Band-Gap Energy and the Electrical Conductivity in MPr₂W₂O₁₀ Tungstates (Where M = Cd, Co, Mn)

76%
Sawicki B., Tomaszewicz E., Piątkowska M., Groń T., Duda H., Górny K.
|
EN
The values of the direct allowed energy gap determined from the UV-vis-NIR measurements and Kubelka-Munk transformation decrease from 3.38 via 2.70 to 2.42 eV for MPr₂W₂O₁₀ in the sequence M = Cd, Co, Mn, while the values of the activation energy increase from 0.11 via 0.44 to 0.47 eV in the same sequence. In other words, the higher the activation energy, the smaller the energy gap. Because the energy gap is typical for insulators, so electron transport phenomena are considered under the Poole-Frenkel effect and small-polaron mechanism.
18
Content available remote

Electrical Properties of Sr₂InV₃O₁₁

76%
Groń T., Filipek E., Pacześna A., Urbanowicz P., Sawicki B., Duda H.
|
EN
The electrical conductivity σ (T) and thermoelectric power S(T) measurements of Sr₂InV₃O₁₁ showed the insulating state and the change of sign of thermopower from p to n at T_{n-p}=400 K. The I-V characteristics provided the evidence of symmetrical and non-linear behaviour typical of strong emission of charge carriers induced by temperature and voltage. Relative dielectric permittivity ε_{r} as well as loss tangent (tan δ) strongly depend both on the temperature in the range of 295-400 K and the frequency in the range of 5×10² to 1×10⁶ Hz, showing the broad maximum at 320 K. These effects are considered as a relaxation process like in the Maxwell-Wagner or Jonscher model as well as the conduction of electric current, as determined by the Joule-Lenz law.
19
Content available remote

Influence of Substitution of the Chromium Ions by the Nonmagnetic Sb and Al Ions on the Magnetization Processes in CuCr_{2}X_{4} ( rm X = S, Se) Spinels

64%
Malicka E., Krok-Kowalski J., Warczewski J., Groń T., Duda H., Mydlarz T., Pawełczyk M., Pacyna A., Rduch P., Władarz G.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
967-968
EN
Both the dc and ac magnetic susceptibilities as well as magnetization measurements were used to study the influence of the dilution of the magnetic chromium subarray by nonmagnetic antimony and aluminium ions on the magnetization processes for four spinel families under investigation. Substitution of the chromium ions by the nonmagnetic Sb and Al ions in the compounds under study leads to the very hard magnetization in the case of the compounds with Sb and very easy magnetization in the compounds with Al. This effect is connected with the electronic configurations of the Sb and Al ions as well as with ionic radii of these cations.
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