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1
Content available remote

Puzzling Magnetism of Gd_3Cu_4Sn_4

100%
Łątka K., Pacyna A., Pöttgen R., Schappacher F.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1501-1508
EN
A polycrystalline, single phase sample of Gd_3Cu_4Sn_4 (Gd_3Cu_4Ge_4 type, Immm, a = 1473.5(1), b = 694.1(1), c = 447.2(1) pm) was synthesized by arc-melting of the elements and subsequent annealing of the sample at 1220 and 970 K, respectively. The magnetic properties of this compound were studied thoroughly by AC and DC magnetic susceptibility measurements and ^{155}Gd Mössbauer spectroscopy. These results reveal two antiferromagnetic phase transitions close to 13 and 8.6 K, respectively. The thermal variation of the magnetic hyperfine fields observed at two inequivalent Gd sites point to two magnetic substructures, which order independently.
2
Content available remote

Phase Transitions in ErFe_{1-x}Al_{x}O_{3} System (x ≤ 0.1)

100%
Bombik A., Pacyna A., Witek W.
Acta Physica Polonica A
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1994
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vol. 85
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issue 2
263-266
EN
The magnetic measurements for some representatives of ErFe_{1-x}Al_{x}O_{3} system were performed. The obtained results indicate an essential influence of nonmagnetic substitution on physical behaviour of examined compounds.
3
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Properties of SmT_{2}Sn_{2} (T = Ni,Cu) Phases

100%
Görlich E. A., Kmieć R., Łątka K., Pacyna A.
Acta Physica Polonica A
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1997
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vol. 92
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issue 2
319-322
EN
Ternary compounds SmNi_{2}Sn_{2} and SmCu_{2}Sn_{2} were investigated with the X-ray diffraction, magnetic susceptibility and electric resistivity methods, as well as using the ^{119}Sn Mossbauer effect under the applied magnetic field. Magnetic susceptibilities of these compounds show the Curie-Weiss behaviour in the temperature range from 15 K to 280 K with the enhanced values of the temperature independent term χ_{0}. Both resistivity and magnetic measurements indicate the occurrence of the magnetic ordering in SmCu_{2}Sn_{2} below T_{N} = 8 K. The Mossbauer investigations carried out at 4.2 K under an applied magnetic field of up 6 T indicate a more complex magnetic structure and a considerable anisotropy. SmNi_{2}Sn_{2} remains paramagnetic down to 5 K.
4
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High Spin-Low Spin Transitions in Cu_{0.2}Co_{0.76}Cr_{1.83}Se_4 Semiconductor

88%
Maciążek E., Groń T., Pacyna A., Mydlarz T., Krok-Kowalski J.
Acta Physica Polonica A
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2012
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vol. 121
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issue 3
687-689
EN
Magnetization, ac and dc magnetic susceptibility measured in the zero-field-cooled mode were used to study the high spin-low spin transitions in polycrystalline Cu_{0.2}Co_{0.76}Cr_{1.83}Se_4 semiconductor. The real part component of fundamental susceptibility χ_1' (T) and its second (χ_2) and third (χ_3) harmonics revealed two spectacular peaks at 128 K and at 147 K, confirming the appearance of the spin-crossover phenomenon.
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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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.
9
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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.
10
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Spin Crossover in Cu_{x}Co_{y}Cr_{z}Se_4 Semiconductors

76%
Maciążek E., Groń T., Pacyna A., Mydlarz T., Zawisza B., Krok-Kowalski J.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
711-713
EN
Magnetization and magnetic susceptibility measured in the zero-field-cooled mode were used to study the spin crossover transition in polycrystalline Cu_{x}Co_{y}Cr_{z}Se_4 compounds. With increasing Co content a transition from ferromagnetic order via ferrimagnetic one to antiferromagnetic-like behaviour was observed. This transition is accompanied with a lowering symmetry from cubic to monoclinic and for the latter the spin crossover phenomenon occurs. These results are considered in a framework of the ligand-field split and the spin-orbit coupling.
11
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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.
12
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Magnetic Coupling in CuCr_2X_4 (X = S, Se) Spinel Compounds Obtained via Substitution of the Chromium Ions by Nonmagnetic Sb or Al Ions

76%
Krok-Kowalski J., Malicka E., Władarz G., Groń T., Pawełczyk M., Heimann J., Pacyna A.
Acta Physica Polonica A
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2011
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vol. 119
|
issue 5
705-707
EN
Taking into account both the dc magnetic susceptibility and the magnetization measurements as well as the high-temperature expansion of the magnetic susceptibility procedure the hopping integrals and superexchange integrals for the first and second coordination sphere were evaluated. The two hopping integrals are positive and many times greater than the superexchange ones. The obtained results testify to that in the stoichiometric compounds under study the double-exchange magnetic interaction is the main mechanism responsible for very strong, ferromagnetic coupling. Using the total hopping integral B the bandwidth of mixed valence band of chromium ions was determined.
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
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Specific Heat and Magnetic Properties of Single-Crystalline (Zn_{0.925}In_{0.054})[Cr_{1.84}In_{0.152}]Se_4 Semiconductor

76%
Malicka E., Groń T., Pacyna A., Ślebarski A., Goraus J., Gągor A., Mydlarz T.
Acta Physica Polonica A
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2012
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vol. 122
|
issue 6
1108-1110
EN
An antiferromagnetic order with a Néel temperature T_{N} = 17.5 K, a strong ferromagnetic exchange evidenced by a positive Curie-Weiss temperature θ_{CW} = 77.3 K, the fuzzy peaks in the real component of susceptibility χ'(T) and the disappearance of the second critical field were established. The curvature of specific heat C(T) and C(T)/T in surrounding of T_{N} indicated a broad peak, characteristic for the system with inhomogeneous magnetic state (spin-glass-like phase). The calculated magnetic entropy showed the value of S(T) ≈ 1 J/(mol K) which is extremely small; i.e., much lower than the magnetic contribution Rln(2S + 1) = 11.52 J/(mol K) calculated for the spin 3/2.
15
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}.
16
Content available remote

Magnetoelastic Phase Transitions and Critical Behaviour of (Fe_{1-x}Ni_{x})_{2}P System

64%
Średniawa B., Duraj R., Pacyna A., Bombik A., Zach R., Bacmann M., Fruchart D., Nizioł S., Fornal P., Stanek J.
Acta Physica Polonica A
|
2000
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vol. 97
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issue 5
921-925
EN
This report focuses on magnetoelastic properties and critical behaviour of (Fe_{1-x}Ni_{x})_{2}P system. For low Ni content (x=0.01) an isolated critical point was found. Analysis of this critical behaviour in the frame of molecular field approximation was carried out. Moreover, thermal variations of the lattice parameters, as measured by X-ray diffraction techniques, were studied. The (P,T) phase diagrams obtained for several Ni contents show the evidence that the Curie temperature decreases with pressure. The Mössbauer spectra collected for x = 0.025, 0.1, 0.2, 0.25 at different temperatures are also analysed. The existence of two nonequivalent crystallographic sites occupied by iron atoms as well as local magnetic structure is discussed.
17
Content available remote

Magnetic Structure of RNiGe and RPdSn Compounds

64%
André G., Bourée F., Bombik A., Oleś A., Sikora W., Kolenda M., Szytuła A., Pacyna A., Zygmunt A.
Acta Physica Polonica A
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1994
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vol. 85
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issue 2
275-278
EN
Magnetic properties including magnetic structure of ternary RNiGe (R = Tb-Er) and RPdSn (R = Ce, Tb-Ho) compounds are determined. In low temperatures an antiferromagnetic ordering is observed. For compounds with R = Tb-Er the magnetic structure changes with temperature.
18
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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