Magnetic properties and magnetic structure of DyCoSi_{2} compound

The results of new magnetic dc and neutron diffraction measurements of $DyCoSi_{2}$ compound are presented. Below $T_{N}$ equal to 10.9 K the Dy moments form collinear G-type structure with the moment parallel to the c-axis. The value of Dy-moment equal to $5.5(2) _{\mu B}$ are smaller than free $Dy^{3+}$ ion value ($10.0 _{\mu B}$). These and the three-step magnetization process indicate the strong influence of the crystal electric field on the stability of the magnetic order. Increase of the values of the lattice parameters at 1.5 K in reference of these at 20 K indicate magnetostriction effect at low temperatures

Magnetic structures of Ho5Rh4Ge10Ho_{5}Rh_{4}Ge_{10}

A powder diffraction measurement of $Ho_5Rh_4Ge_{10}$ is reported. This compound crystallizes in the tetragonal $Sc_5Co_4Si_{10}$-type structure (space group P4/mbm) in which the Ho atoms occupy three different sites. The neutron diffraction measurements indicate antiferromagnetic order with the Néel temperature $T_{N}$=7 K. Below $T_{N}$ an additional phase transition at 4.5 K connected with the change of the magnetic structure is observed. The Ho moments in 4(h) site form collinear order up to T_{N} while moments at 2(a) site form sine modulated structure. Determined experimentally magnetic structures are compared to the results of symmetry analysis

Size effects in antiferromagnetic NiO nanoparticles

X-ray and neutron diffraction as well as magnetometric methods were used in order to investigate crystal and magnetic structure together with magnetic properties of nickel oxide NiO obtained from thermal decomposition of Ni(OH)$_{2}$. It has been found that crystal unit cell volume and crystal unit cell deformation parameter decrease with increasing decomposition temperature $T_{d}$ while grain size increases. The results of magnetization, magnetic susceptibility and neutron diffraction measurements reveal a formation of antiferromagnetic order with uncompensated magnetic moment below the Néel temperature. Magnetization together with coercive field decreases with increasing $T_{d}$. The neutron diffractogram of sample obtained at 240°C indicates broadening of both the peaks of nuclear and magnetic origin. The magnetic ordering may be described by a propagation vector $k = \left [ \frac{1}{2}, \frac{1}{2}, \frac{1}{2} \right ]$

Neutron diffraction studies of nanoparticle DyMnO_{3} compound

The neutron powder diffraction (NPD) measurements of the nano-size DyMnO3 manganite have been performed. The obtained results indicate that this compound crystallizes in the orthorhombic crystal structure described by the space group Pnma. The Mn and Dy moments order antiferromagnetically at different temperatures and form modulated magnetic structure described by the propagation vector k = (kx; 0; 0) with the different values of kx component for the Mn and Dy sublattices. The values of kx component for Mn sublattice increase with decreasing of the temperature and are smaller that in bulk compound. The wide Bragg peaks related to the Dy sublattice suggest that the magnetic order in this sublattice has the cluster-like character

Neutron diffraction studies of NdNi_{5}Sn compound

The neutron powder diffraction measurements of the NdNi5Sn compound have been performed. The obtained results indicate that this compound crystallizes in a hexagonal CeNi_{5}Sn-type crystal structure described by the space group P63/mmc. The parameters of the crystal structure at 1.55 and 14.8 K are determined. In contradiction to the magnetic data the long-range magnetic ordering was not detected up to 1.55 K

Crystal and magnetic structures of R2R_2Ni2_2In compounds (RR = Tb and Ho)

Crystal and magnetic structures of $R_2$Ni$_2$In ($R$ = Tb and Ho) have been studied by powder neutron diffraction at low temperatures. The compounds crystallize in an orthorhombic crystal structure of the Mn$_2$AlB$_2$-type. At low temperatures, the magnetic moments localized solely on the rare earth atoms form antiferromagnetic structures. The Tb magnetic moments, equal to 8.65(6) $\mu_B$ and parallel to the $c$-axis, form a collinear magnetic structure described by the propagation vector $\boldsymbol{k} = [\frac{1}{2}, \frac{1}{2}, \frac{1}{2}]$. This magnetic structure is stable up to the N\'eel temperature equal to 40 K. For Ho$_2$Ni$_2$In a complex, temperature-dependent magnetic structure is detected. In the temperature range 3.5-8.6 K, an incommensurate magnetic structure, described by the propagation vector $\boldsymbol{k}_1 = [0.76, 0, 0.52]$ is observed, while in the temperature interval 2.2-3.1 K the magnetic order is described by two propagation vectors, namely, $\boldsymbol{k}_2 = [\frac{5}{6}, 0.16, \frac{1}{2}]$ and its third harmonics $3\boldsymbol{k}_2 = [\frac{5}{2}, 0.48, \frac{3}{2}]$. Below 2 K, a coexistence of all magnetic structures detected at higher temperatures is observed. For all magnetic phases, the Ho magnetic moments are parallel to the $c$-axis. The low temperature heat capacity data confirm a first order transition near 3 K

Valence band of Ce2Co0.8Si3.2Ce_{2}Co_{0.8}Si_{3.2} and Ce2RhSi3Ce_{2}RhSi_{3} studied by resonant photoemission spectroscopy and FPLO calculations

This work presents studies of the valence band of two Kondo lattice systems: Ce2Co0.8Si3.2, which is paramagnetic with the Kondo temperature T-K approximate to 50 K and Ce2RhSi3, which is antiferromagnetic below T-N = 4.5 K and exhibits TK approximate to 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 Ce2Co0.8Si3.2. The off-resonance photoemission data reveal that a maximum in the 3d electron density of states is shifted towards EF for Ce2Co0.8Si3.2 as compared to Ce2RhSi3. 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 EF is observed for Ce2CoSi3. The calculations also reveal the existing tendencies for antiferromagnetic and ferromagnetic ground states in a case of Ce2RhSi3 and Ce2CoSi3, respectively

Badanie własności magnetycznych i struktury elektronowej związków międzymetalicznych RTX o strukturze rombowej : praca doktorska wykonana w Zakładzie Fizyki Ciała Stałego Instytutu Fizyki Uniwersytetu Jagiellońskiego, pod kierunkiem Andrzeja Szytuły, przedstawiona Radzie Wydziału Fizyki i Informatyki Stosownej Aklademii Górniczo-Hutniczej /

Praca broniona w 2006r.Recenzenci pracy: Andrzej Ślebarski, Andrzej Kozłowski.Praca doktorska. Akademia Górniczo-Hutnicza im. Stanisława Staszica (Kraków), 2006.Bibliogr. k. 91-93.Oddziaływania magnetyczne, wymienne, pole krystaliczne, podstawy fizyczne wybranych metod doświadczalnych, dyfrakcja neutronów na kryształach, spektroskopia fotoelektronów, źródła promieniowania, analiza energii elektronów, detekcja, podstawy fizyczne zjawiska fotoelektrycznego, eksperyment, preparatyka próbek, przyrządy pomiarowe wykorzystywane w badaniach, metody opracowywania danych doświadczalnych, opracowanie dyfraktogramów, metoda Rietvelda, opracowanie widm fotoemisyjnych, struktura krystaliczna, własności magnetyczne związków RTX, własności magnetyczne związków RniSi, R = Tb – Er, struktura magnetyczna TbNiSi, DyNiSi, HoNiSi, ErNiSi, RruGe, R = Gd – Er, TbRuGe, HoRuGe, ErRuGe, RrhSi, R = Tb, Dy, Ho, Er, TbRhSi, DyRhSi, HoRhSi, ErRhSi, RrhGa, R = Tb, Ho i Er, TbRhGa, HoRhGa, ErRhGa, RrhGe, R = Gd – Tm, HoRhGe, ErRhGe, TmRhGe, RpdGa, R = Gd – Er, TbPdGa, HoPdGa, ErPdGa, RirSi, R = Tb – Er, TbIrSi, HoIrSi, ErIrSi, RirGe, R = Gd – Er, TbIrGe, HoIrGe, ErIrGe, RptSi, R = Gd – Er, TbPtSi, DyPtSi, HoPtSi, ErPtSi, RptGa, R = Gd – Er, TbPtGa, DyPtGa, HoPtGa, ErPtGa, RptGe, R = Gd – Er, TbPtGe, DyPtGe, ErPtGe, pomiary metodą spektroskopii fotoelektronów, moment magnetyczny, pole krystaliczne, formalizm Bertau

Crystal structure of synthetic feroxyhite δ\delta-FeOOH studied with neutron diffraction

The synthetic polycrystalline sample of $\delta$-FeOOH was investigated by means of neutron diffraction. Based on these data, the parameters of the crystal structure are determined. This compound crystallizes in the hexagonal structure described by the space group P$\bar{3}$m1, in which the oxygen O$^{2-}$ ions in the 2d site form the octahedral network. The Fe$^{3+}$ ions randomly occupy the 1a (53%) and 1b (47%) sites, and the hydrogen atoms half-occupy two positions in the 2d site. The magnetic contribution to the neutron diffraction pattern is very small and does not give possibility to determine the magnetic structure