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Content available remote Magnetyczne diagramy fazowe związków R1‑XR'XMn2(Ge, Si)2
W artykule omówiono klasyczny fenomenologiczny model pola średniego opisujący dwupodsieciowy magnetyk. Podstawowym założeniem modelu jest liniowa zależność stałej wymiany od objętości komórki elementarnej, którego konsekwencją jest występowanie zjawiska magnetostrykcji w przejściach fazowych I rodzaju. W oparciu o dane eksperymentalne układów R1‑XR'XMn2(Ge, Si)2, w tym diagramy fazowe (P,T), oszacowano parametry modelu i przedyskutowano otrzymane wyniki teoretyczne.
A phenomenological standard two-sublattice mean-field model was discussed. The Mn-Mn interaction is assumed to be linearly dependent on the unit-cell dimensions, giving rise to magnetostrictive phenomena. The (P,T) magnetic phase diagram for R1‑XR'XMn2(Ge, Si)2 series of compounds was discussed and the magnetic phase diagram parameters derived from the experimental data were used for the theoretical calculation.
Content available remote The electronic and magnetic properties of Nd5Co19B6 and Nd5Co21B4 compounds
The Nd5Co19B6 and Nd5Co21B4 compounds were manufactured as promising systems suitable for fabrication of permanent magnets. They belong to the Rm+nCo5m+3nB2n family having the P6/mmm space group. The band structure calculations are performed by the tight binding version of the linear muffin-tin orbital method in the atomic sphere approximation (TB-LMTO ASA). The calculated magnetic moments on Co atoms depend on their local environment. The calculated values are compared with the bulk measurements.
Content available remote Magnetic properties of (Eu,Gd)Te semiconductor layers
In (Eu,Gd)Te semiconductor alloys a well known antiferromagnetic semiconductor compound EuTe is transformed into n-type ferromagnetic alloy. This effect is driven by the RKKY interaction via conducting electrons created due to substitution of Gd3+ for Eu2+ ions. It is expected that due to the high degree of electron spin polarization (Eu,Gd)Te can be exploited in new semiconductor spintronic heterostructures as a model injector of spin-polarized carriers. The (Eu,Gd)Te monocrystalline layers with Gd content up to 5 at. % were grown by MBE on BaF2 (111) substrates with either PbTe or EuTe buffer layers. The measurements of magnetic susceptibility and magnetization revealed that the ferromagnetic transition with the Curie temperature TC=11- 15 K is observed in (Eu,Gd)Te layers with n-type metallic conductivity. An analysis of the magnetization of (Eu,Gd)Te was carried out in a broad range of magnetic fields applied along various crystal directions both in- and out-of layer plane. It revealed, in particular, that a rapid low field ferromagnetic response of (Eu,Gd)Te layer is followed by a paramagnetic-like further increase towards the full saturatio
Content available remote Magnetic interaction in RTxX2 ternary compounds
This work is an attempt of systematization the magnetic properties of the RTxX2 (R-rare earth, T-transition metal, X=Si, Ge, Sn) compounds crystallizing in the orthorhombic CeNiSi2 type structure. All silicides crystallize in the stoichiometric structure RTX2 while germanides and stannides form mainly defected structures RTxX2 (where 0
Content available remote Electronic structure of the intermetallic rare earth compounds
The electronic structures of intermetallic rare earth compounds of different compositions: RMn2Ge2 (R = Nd, Sm), R3Mn4Sn4 (R = La, Ce, Nd), Ce3Ag4X4 (X = Ge, Sn), and Ce2MnGe6, have been investigated. XPS measurements were performed using a commercial LHS10 spectrometer. The valence band and core-level states have been analysed. In Mn compounds, the Mn 3d state forms a broad band near the Fermi level. The analysis of XPS spectra using the Gunnarsson-Schönhammer model gives the coupling parameters (hybridisation energy) between the R 4f states and electrons of the conduction band
Content available remote Electrical resistivity of RNi4Al and RNi4Cu
A comparative studies of the temperature dependence of resistivity for RNi4X (X = Al, Cu; R = Y or rare earth) compounds are presented. These results are also compared to the previously studied RNi4B. The ordering temperatures are well identified on the ?(T) curves. The residual resistivity ?0 of RNi4Al is several times higher than for RNi4Cu and RNi4B. The YNi4X compounds are included in these studies as the nonmagnetic isostructural reference materials. The phonon contribution has been determined for both Y-based compounds employing the Bloch-Grüneisen formula. The CeNi4X compounds show a shallow minimum in ?(T) at low temperatures (about 15 K). This anomaly has been ascribed to a Kondo impurity - like behavior. For the other rare earths, the ?(T) dependences below TC have been analyzed assuming the scattering on magnons as the predominant mechanism.
Content available remote Effect of spin-orbit coupling on the electronic structure of bismuthide YbAuBi
The electronic structure of ternary ytterbium YbAuBi and YbAuSn compounds was studied by X-ray photoemission spectroscopy (XPS) and ab-initio methods (LMTO-ASA, FP-LMTO, FPLO). The results showed that the valence bands in these compounds were formed by 4f orbitals of ytterbium and 5d orbitals of transition metals. The full relativistic band calculations (FP LMTO and FPLO) with spin-orbit coupling had shown that 4f peak consisted of two peaks that corresponded to Yb 4f7/2 and 4f5/2 doublet.
The compounds of the Rn+1Co3n+5B2n family crystallize in a hexagonal structure having the P6/mmm space group. The ab initio spin-polarized band structure calculations have been performed based on the tight-binding linear muffin-tin orbitals method (TB LMTO) for the following five representatives of the family: RCo5, RCo4B, R3Co11B4, R2Co7B3 and RCo3B2, where R=Gd or Tb. The cobalt atoms occupying distinct sites have different types and numbers of neighbouring atoms and as a consequence the magnetic moments are different. The calculated values are compared with the bulk measurements.
Content available remote Eksperymentalne badania wzdłużnych pasywnych łożysk magnetycznych
W referacie zawarto opis stanowiska, metodykę i wyniki badań dynamicznych jednostronnych i dwustronnych pasywnych łożysk magnetycznych. Przykładowo podano eksperymentalne przebiegi nośności, strat brodzenia oraz zmianę współczynnika tłumienia w funkcji prędkości obrotowej wirnika i różnych wartości szczeliny łożysk wykonanych z magnesów NdFeB.
The paper presents the description of a research stand, methodology and results of dynamic research of single- and double-acting passive magnetic bearings. It describes exemplary experimental runs of the curves of the carrying load ability, fording loss and the change of the vibration damping coefficient in the function of the rotor rotational speed for different gap values of bearings made of NdFeB magnets.
Content available remote Rare earth oxide films: their preparation and characterization
Summarises the results of our investigations dealing with preparation of rare earth oxide films and examinations of their physical properties. Different deposition methods have been applied for fabrication of these films and rare-earth-oxide-based thin film coatings. The main results concerning film microstructure and optical properties in the wavelength range from the UV up to the IR are presented. Electrical and dielectric studies have been carried out in the time domain and in the frequency domain (from very low frequencies up to radio frequencies) for selected rare earth oxides. MIM sandwich-type structures have been fabricated for this aim. Trapping levels in these oxides have been investigated. The complex impedance diagnostics was applied to the analysis of the volume of the R/sub 2/O/sub 3/ film and interfacial properties (metal/insulator barriers) of M/R/sub 2/O/sub 3//M thin film structures.
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