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  1. 49 Acta Physica Polonica A

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  1. 7 Szytuła A.

  2. 4 Penc B.

  3. 3 Giebultowicz T.

  4. 3 Szajek A.

  5. 3 Zygmunt A.

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1
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Magnetic Structure of RNiGe and RPdSn Compounds

100%
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.
2
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Magnetic Structure in UIrAl

100%
Prokeš K., Prchal J., Sechovský V., Andreev A.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
339-342
EN
By means of neutron diffraction on a hexagonal UIrAl single crystal we find that this system orders ferromagnetically at low temperatures with magnetic moments of 0.93 (10) μ_B aligned along the c axis. The Curie temperature T_C = 65 (5) K determined from the diffraction experiment is in good agreement with bulk magnetic measurements.
3
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Uranium Intermetallics in High Magnetic Fields: Neutron Diffraction Experiments

100%
Prokeš K.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
209-214
EN
The neutron diffraction is an indispensable technique for the determination of magnetic structures. Due to a rather large penetration depth of neutrons in many materials one can construct complicated sample environments necessary to prepare the desired magnetic phase of the material under study. Combination of magnetic fields, low temperatures, and high hydrostatic or uniaxial pressures are possible. Capabilities of this technique are demonstrated on a few experimental results obtained on uranium UTX (T: transition metal, X: p-element) compounds.
4
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Magnetic Properties of the RCoSn (R=Tb-Er) and RRhGe (R=Ce, Nd) Compounds

100%
Bażela W., Leciejewicz J., Małetka K., Szytuła A., Zygmunt A.
Acta Physica Polonica A
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1994
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vol. 85
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issue 5
859-862
EN
Magnetic properties of orthorhombic RCoSn (R = Tb-Er) and RRhGe (R = Ce,Nd) (of the TiNiSi-type of crystal structure), were studied by magnetometric and neutron diffraction methods. All RTX compounds order antiferromagnetically at low temperatures. The magnetic structure of TbCoSn and HoCoSn is sine-wave-modulated with the wave vectors k_{1} = (0, 0.25, 0.11) and k_{2} = (0, 0.333, 0), respectively. The magnetic structures of CeRhGe and NdRhGe compounds are collinear (C mode). Magnetic moments of 1.4(2) and 2.0(2) μ_{B} localized respectively on Ce and Nd ions, are aligned along the a-axis.
5
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Mössbauer Investigation of Spin Arrangements in Er_{2-x}Ce_xFe_{14}B

63%
Bogacz B., Pędziwiatr A.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1509-1516
EN
It was theoretically postulated earlier that in compounds Er_{2-x}Ce_{x}Fe_{14}B it may be possible to observe not only axial and planar spin arrangements but also a conical one. In order to experimentally verify this hypothesis, ^{57}Fe Mössbauer spectroscopy analysis was used to study the polycrystalline compounds Er_{2-x}Ce_{x}Fe_{14}B in the postulated composition region (x = 1.0, 1.1, 1.2, 1.3) in the wide range of temperatures. The obtained experimental data do not clearly support the suggestion of conical arrangement occurrence in the postulated compositions. They indicate that such phenomenon may be shifted towards higher Ce content.
6
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Mössbauer and Magnetometric Studies of Spin Reorientations in Er_{2-x}Th_xFe_{14}B

63%
Wojciechowska A., Bogacz B., Pędziwiatr A.
Acta Physica Polonica A
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2006
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vol. 109
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issue 3
427-432
EN
The Er_{2-x}Th_xFe_{14}B (x=0.5, 1.0, 1.5) polycrystalline compounds have been investigated with ^{57}Fe Mössbauer spectroscopy in the 50-330 K temperature range and magnetometry in the temperature range of 4.2-340 K. Initial magnetization vs. temperature measurements allowed us to establish the temperature regions of reorientations and also the Curie temperatures of the compounds. The spin reorientation phenomena (changes from planar to axial spin arrangements) have been studied extensively by a narrow step temperature Mössbauer scanning in the vicinity of the spin reorientation temperatures. From the analysis of the obtained Mössbauer spectra it was deduced that in the region of transition each subspectrum was split into two Zeeman sextets, which were characterised by different hyperfine magnetic fields and quadrupole splittings. A consistent way of describing the Mössbauer spectra in the wide range of temperatures was proposed. The composition and temperature dependences of hyperfine interaction parameters and subspectra contributions were derived from experimental spectra. The transition temperatures were determined for all the compounds studied and the spin phase diagram was constructed.
7
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Magnetic-Form Factor Measurements by Polarised Neutron Scattering: Application to Heavy Fermion Superconductors

63%
Neumann K., Ziebeck K.
Acta Physica Polonica A
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1993
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vol. 84
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issue 1
43-81
EN
The experimental technique of spin polarised neutron scattering as used in magnetic form factor measurements is presented. An introduction to the interpretation and the calculation of magnetic form factors and magnetization densities is given. The experimental technique of neutron scattering theory as applied to elastic spin polarised scattering experiments is briefly introduced. The calculation of the magnetic form factor and the magnetization densities are considered for simple model systems such as a collection of localised magnetic moments or an itinerant electron system. The discussion is illustrated by an experimental investigation of the magnetic form factor in the heavy fermion superconductors UBe_{13} and UPt_{3}. Magnetization density maps and magnetic form factors are presented, and their implications for other physical quantities are briefly discussed.
8
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The Electronic and Magnetic Properties of the USn_2 Compound

63%
Szajek A.
Acta Physica Polonica A
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2004
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vol. 105
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issue 5
485-493
EN
The ab initio self-consis tent calculations were performed for USn_2 compound, which crystallizes in the ZrGa_2-type structure (Cmmm space group). The tight binding linear muffin-tin orbital method in the atomic sphere approximation was used in the calculations. The spin-polarized calculations confirmed the antiferromagnetic order in the USn_2 system. The magnetic moment is predominantly located on the uranium atoms and is formed mainly by the f electrons. The three types of Sn atoms may be treated as non-magnetic.
9
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X-Ray Absorption and Experiments with Circularly Polarized Radiation

63%
Schmiedeskamp B.
Acta Physica Polonica A
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1994
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vol. 86
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issue 5
675-693
EN
Absorption of circularly polarized radiation (σ-radiation) recently gained interest mainly due to its helicity-dependence for magnetic materials (circular magnetic dichroism). The physics behind this absorption process is optical orientation and is closely related to the physics behind other types of experiment with circularly polarized radiation in which fundamental electronic properties of matter are studied. The consideration of X-ray absorption plays also a role in the development of new beam lines for σ-radiation. An important part in a beamline for σ-radiation in the soft X-ray range can be multilayer optics. The role of absorption in the design of these optics is discussed as well as different types of experiment with circularly polarized radiation: the physical mechanism of optical orientation is applied to gain insight into both magnetic and fundamental electronic properties of matter.
10
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Static and Dynamic Spin Organization in Magnetic Semiconductor Nanostructures

63%
Samarth N., Luo H., Furdyna J., Giebultowicz T., Awschalom D.
Acta Physica Polonica A
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1992
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vol. 82
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issue 4
573-584
EN
We describe experiments which study static and dynamic aspects of Mn spin organization in magnetic semiconductor superlattices and quantum wells. Neutron diffraction studies of ZnSe/MnSe and ZnTe/MnSe superlattices show how static Mn spin organization in these antiferromagnetic layers may be modified by strain and lowered dimensionality. We also use a novel form of femtosecond magnetic spectroscopy to examine magnetic polaron dynamics in diluted magnetic semiconductor quantum wells, and show how the organization of Mn spins by a spin-polarized carrier population may be directly viewed in the time domain.
11
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Synchrotron Radiation Diffraction Studies of Magnetic Materials

63%
Brückel T.
Acta Physica Polonica A
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1997
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vol. 91
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issue 4
669-679
EN
Since the advent of high brilliance synchrotron radiation sources, magnetic X-ray diffraction has become a standard microscopic probe for the investigation of magnetic structures, magnetic phase transitions and magnetic disorder phenomena. Modern experiments highlight the complementarity of this new probe to the standard neutron diffraction technique by taking advantage of the high momentum space resolution, the element sensitivity, the possibility to separate spin- and orbital contributions etc. In this paper we present selected experiments performed at HASYLAB which exemplify the present possibilities of resonant and non-resonant magnetic X-ray diffraction.
12
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Correlation between Magnetic Phases and Insulator-Metal Transition in La_{1/3}Nd_{1/3}Ca_{1/3}MnO_{3} Perovskite

63%
Baszyński J., Idzikowski B., Toliński T., Hoser A.
Acta Physica Polonica A
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2000
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vol. 97
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issue 5
779-782
EN
The La_{1/3}Nd_{1/3}Ca_{1/3}MnO_{3} ceramic perovskites are investigated using the neutron diffraction technique and resistance measurements in the temperature range from 260 K down to 5 K. We have found that the integrated intensity of the antiferromagnetic peaks was growing with decreasing temperature and reached the maximum at a temperature about 20 K lower than that of the semiconductor-metal transition and did not vanish at 5 K. The semiconductor-metal transition is correlated with the temperature of the maximum of the lattice c-parameter and the percolation of ferromagnetic domains. Our results suggest that although the ferromagnetic long-range order is established through the semiconductor-metal transition induced percolation network, locally the antiferromagnetic correlation can remain.
13
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Phase Separation in Hubbard Model

63%
Samson J. H.
Acta Physica Polonica A
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1997
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vol. 92
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issue 2
363-366
EN
The Hartree-Fock ground-state phase diagram of the one-dimensional Hubbard model is calculated in the μ-U plane, restricted to phases with no charge density modulation. This allows antiferromagnetism, saturated ferromagnetism, spiral spin density waves and a collinear structure with unit cell ↑↑↓↓. The spiral phase is unstable against phase separation near quarter-, half- and three-quarter-filling. For large U this occurs at hole (or electron) doping of (3t/π^{2}U)^{1/3} from half-filling.
14
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Neutron Diffraction Study of Ferromagnetic Ordering in La_{1/3}Nd_{1/3}Ca_{1/3}MnO_{3} Induced by Electric Field

63%
Baszyński J., Idzikowski B., Toliński T., Hoser A.
Acta Physica Polonica A
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2000
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vol. 97
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issue 5
831-834
EN
We used the neutron diffraction technique to study the ferromagnetic ordering process in La_{1/3}Nd_{1/3}Ca_{1/3}MnO_{3} induced by the short impulse of the external electric field E=4 V/cm at a magnetic field H=1.5 T. Our sample was prepared by the standard solid-state reaction. The diffraction measurements at 4 K, carried out for the neutron wavelength λ=0.2442 nm, have revealed the orthorhombic perovskite structure with the unit-cell parameters: a=0.5480 nm, b=0.5550 nm and c=0.7737 nm. We observed that a short impulse of the electric field develops the ferromagnetic ordering in a similar way as the magnetic field up to 4 T. We assume that the increased ferromagnetic ordering induced by the external electric field at a given magnetic field has the same physical origin as in the case of the Zener double exchange. The effect is confirmed by magnetic moment measurements using vibrating sample magnetometer.
15
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Correlations in Magnetic-Nonmagnetic Semiconductor Superlattices - Simple Model

63%
Blinowski J., Kacman P.
Acta Physica Polonica A
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1997
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vol. 92
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issue 4
719-723
EN
The magnetic interactions in superlattices formed by alternating layers of magnetic and nonmagnetic semiconductors with common anions were studied theoretically. Within a one-dimensional tight-binding model by minimising the total electronic energy we show the existence of an efficient long range mechanism of magnetic correlations between the neighbouring magnetic layers in such superlattices. The cases of magnetic ions in the barriers (e.g., EuTe/PbTe) and in the wells, with the order within the magnetic layers being either ferromagnetic or antiferromagnetic, have been considered and compared with the paramagnetic case. In the case of antiferromagnetic ordering within magnetic layers we have found that for even and odd numbers of magnetic monolayers different magnetic superlattices are energetically favourable.
16
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Neutron Diffraction Studies of MnFeAs_{y}P_{1-y} System

63%
Zach R., Bacmann M., Fruchart D., Soubeyroux J., Nizioł S., Fruchart R.
|
EN
Magnetic structures of the MnFeAs_{y}P_{1-y} system were examined by means of the neutron diffraction technique in the 1.5-300 K temperature range. Atomic ordering in the metal sublattices, temperature dependence of the incommensurate (y = 0.2 and y = 0.275) and of the ferromagnetic (y = 0.275, y = 0.3, y = 0.5) ordering is discussed.
17
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Magnetic Structure and Phase Diagram of TmB_4

63%
Gabáni S., Maťaš S., Priputen P., Flachbart K., Siemensmeyer K., Wulf E., Evdokimova A., Shitsevalova N.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
227-230
EN
Magnetic structure of single crystalline TmB_4 has been studied by magnetization, magnetoresistivity, and specific heat measurements. A complex phase diagram with different antiferromagnetic phases was observed below T_{N1}=11.7 K. Besides the plateau at half-saturated magnetization (1/2 M_S), also plateaus at 1/9, 1/8 and 1/7 of M_S were observed as a function of applied magnetic field Bparallel c. From additional neutron scattering experiments on TmB_4, we suppose that these plateaus arise from a stripe structure which appears to be coherent domain boundaries between antiferromagnetic-ordered blocks of 7 or 9 lattice constants. The received results suggest that the frustration among the Tm^{3+} magnetic ions, which maps to a geometrically frustrated Shastry-Sutherland lattice, leads to a strong competition between antiferromagnetic and ferromagnetic order. Thus, stripe structures in intermediate field appear to be the best way to minimize the magnetostatic energy against other magnetic interactions among the Tm ions combined with very strong Ising anisotropy.
18
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Electronic Structure and Magnetic Properties οf the UCoAs_{2} Compound

63%
Werwiński M., Szajek A.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
244-246
EN
The UCoAs_{2} compound crystallizes in the tetragonal HfCuSi_{2} type structure with space group P4/nmm. The compound orders ferromagnetically at 150 K with a spontaneous magnetic moment of about 1.8 μ_B per formula unit. We present results of fully relativistic band structure calculations based on the full-potential local-orbital minimum-basis scheme (FPLO-5.10-20) and compare magnetic moments obtained from calculations without and with orbital polarization corrections. The magnetic behavior of the Co atoms remains unknown.
19
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Magnetic Properties of the U_5Ge_4 Compound Based on Ab initio Calculations

63%
Szajek A., Werwiński M., Malinowski W., Leśniak P.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
251-253
EN
U_5Ge_4 crystallizes in a hexagonal Ti_5Ga_4 type structure with two inequivalent crystallographic sites occupied by uranium atoms. The band structure calculations were performed by the full-potential local-orbital minimum basis band structure code. The calculations showed that on both types of uranium atoms small magnetic moments are formed and their values are equal to 0.08 and 0.15 μ_{B}/atom, respectively.
20
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Complex Magnetic Behaviour of Ho_3Cu_4X_4 Compounds (X = Si and Sn)

51%
Gondek Ł., Szytuła A., Prokhnenko O.
Acta Physica Polonica A
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2008
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vol. 113
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issue 4
1179-1184
EN
Ternary Ho_3Cu_4X_4 compounds exhibit very complex magnetic phase diagrams. The rare earth ions occupy two non-equivalent crystal positions. Within both magnetic sublattices, magnetic moments exhibit different magnetic ordering temperatures. Moreover, in light of our results, it seems that both sublattices are weakly coupled between each other. This may be observed as independent changes of propagation vectors etc. The major difference of ordering temperatures between both compounds is likely related to substantial change of interatomic distances. Consequently, completely different crystalline electric field effects are observed.
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