B. Penc

Electronic structure of RTX (R=Pr, Nd; T=Cu, Ag, Au; X=Ge, Sn) compounds

Abstract Electronic structure of ternary RTX (R=Pr, Nd; T=Cu, Ag, Au; X=Ge, Sn) compounds was studied by X-ray photoemission spectroscopy. Core-levels and valence bands were investigated. The XPS valence bands are compared with the ones calculated using the spin-polarized tight binding linear muffin-tin orbital (TB LMTO) method. The obtained results indicate that the valence bands are mainly determined by Cu3d, Ag4d and Au5d bands. The spin–orbit splitting values Δ E LS determined from the XPS spectra of Pr and Nd 3d 5/2 and 3d 3/2 are equal to 20.5 eV for Pr-compounds and 22.5 eV for Nd-compounds. The analysis of these spectra on the basis of the Gunnarsson–Schonhammer model gives a hybridization of f-orbitals with the conduction band.

Neutron diffraction and magnetisation studies of magnetic ordering in RAuIn (R=Tb, Dy, Ho)

Abstract Polycrystalline samples of the RAuIn (R=Tb, Dy, Ho) compounds have been prepared and studied by powder neutron diffraction and magnetisation measurements. These compounds crystallise in the hexagonal ZrNiAl-type structure. They have been found to be antiferromagnets with the Neel temperatures equal: 35 K (R=Tb), 11 K (R=Dy) and 4.8 K (R=Ho). At T=1.5 K the magnetic ordering of TbAuIn and DyAuIn is described by the propagation vector k =(0, 0, 1 2 ) while in the case of HoAuIn by two propagation vectors: k 1 =(0, 1 2 , 1 2 ) and k 2 =(0, 0, 1 2 ). Between T N and T SG =58 K spin-glass behaviour is reported for TbAuIn. For the first time, the two-step magnetic phase transition: From the long-range antiferromagnetic order through a spin-glass-like short-range ordering to a paramagnetic state is experimentally evidenced in this compound.

Magnetic properties and magnetic structures of RCoxSn2 (R=Gd–Er) compounds

Abstract Magnetic properties of RCo x Sn 2 (R=Gd–Er) stannides, determined on the basis of magnetic and powder diffraction data, are reported. The compounds crystallize in the orthorhombic CeNiSn 2 -type structure. Magnetic and neutron diffraction measurements (the latter for R=Tb and Ho) show that all the compounds are antiferromagnets with Neel temperatures of 16.5 K (R=Gd), 18.8 K (R=Tb), 7 K (R=Dy), 5.6 K (R=Ho) and 4.5 K (R=Er). The neutron diffraction data indicate the presence of collinear magnetic structures described by the propagation vector k =(0, 0, 1 2 ) for R=Tb and k =( 1 2 , 1 2 , 0 ) for R=Ho. The determined magnetic structures of RCo x Sn 2 (R=Tb, Ho) are similar to those observed in the isostructural RNi x Sn 2 .

Magnetic structures of RNixSn2 (R=Tb, Ho) compounds

Abstract The magnetic structure of 1:1:2 stannides, determined on the basis of powder neutron diffraction data, is reported. The RNi x Sn 2 (R=Tb, Ho) compounds crystallize in the orthorhombic CeNiSi 2 -type structure. Magnetic and neutron diffraction measurements show that both compounds are antiferromagnets with Neel temperatures of 17.4 K for R=Tb and 6.6 K for R=Ho. The neutron diffraction data indicate the presence of collinear magnetic structures described by the propagation vector k =(0,0, 1 2 ) for R=Tb and k =( 1 2 , 1 2 ,0) for R=Ho. The determined magnetic structures of RNi x Sn 2 are compared with those observed in RNiSn 2 and the isostructural silicides and germanides.

Magnetic structure and magnetic phase transitions in TbPtGe2

Magnetic and neutron diffraction measurements have been performed on TbPtGe2 at low temperatures. The compound crystallizes in the orthorhombic YIrGe2-type structure (space group Immm); crystal structure parameters have been refined on the basis of the neutron diffraction pattern collected at T = 30.7 K (paramagnetic region). TbPtGe2 is antiferromagnetic below TN = 24.2 K. Below this temperature only one of the two Tb sublattices is ordered; the Tb magnetic moments localized at the 4(i) sites order with the simple propagation vector k = 0. Below Tt1 = 11.4 K the magnetic moments at the other Tb sites, 4(h), show an ordering with the propagation vector k1 = [0.2677(8),0.1312(24),0.6989(27)]. At Tt2 = 7 K a further phase transition to a new modulated phase described by the propagation vector k2 = [0.2584(5),0,0.5895(6)] is observed.

Neutron diffraction studies of the magnetic structures of the HoRhGe and ErRhGe compounds

HoRhGe and ErRhGe compounds crystallize in the orthorhombic TiNiSi-type of structure with the space group Pnma. Neutron diffraction measurements at T = 1.6 K indicate collinear magnetic structures with the propagation vector k = (1/2,0,1/2) for HoRhGe and k = (0,1/2,0) for ErRhGe. After increasing the temperature, the change to the incommensurate sine modulated structure is observed for ErRhGe at . The temperature dependence of the magnetic peak intensities gives the N?el temperature 4.6 K for HoRhGe and 9.5 K for ErRhGe.

Magnetic structures and magnetic phase transitions in TbMn0.33Ge2

Abstract A study of the magnetic structure of TbMn0.33Ge2 has been made using a neutron diffractometer of better resolution and new results have been obtained. The paramagnetic neutron diffraction data confirmed the CeNiSi2-type of crystal structure reported earlier for this compound. The magnetic moments are located on terbium. At 1.5 K the Tb magnetic moments have two components: a collinear and sine wave modulated one so the magnetic order at this temperature has a complex character. With increasing temperature, the change of the magnetic structure to the sine wave modulated one is observed near the Neel temperature TN=28 K.

Magnetic ordering of R3Cu4Sn4 (R = Tb, Dy, Ho and Er)

Neutron diffraction studies of polycrystalline R3Cu4Sn4 (R = Tb, Dy, Ho, Er) intermetallic compounds with the orthorhombic Gd3Cu4Ge4-type crystal structure indicate the existence of different magnetic structures. Rare earth atoms occupy two non-equivalent 2d and 4e sublattices. The rare earth magnetic moments order at low temperatures. For R = Tb and Dy the magnetic structures below the Neel temperature are described by the propagation vectors k = (0, 0, 1/2 + δ). In these compounds both rare earth sublattices order. For R = Ho the magnetic structure is more complicated. There are two vectors; one of them is k = (0, 1/2, 0) whereas the second one changes with temperature. For the Er compound there is the propagation vector k = (1/2, 1/2, 0) which describes the magnetic ordering in the 2d sublattice and at low temperatures is accompanied by the propagation vector k = (0, 0,δ) describing the ordering in the 4e sublattice.

Low temperature neutron diffraction study of the CeFe2Al8 compound

Abstract Powder neutron diffraction measurements of the CeFe 2 Al 8 compound at 1.5, 10 and 75 K indicate that this compound crystallizes in an orthorhombic crystal structure (space group Pbam ). The crystal structure parameters of CeFe 2 Al 8 were determined. The low temperature data at T =1.5 K did not reveal magnetic ordering. The magnetization, magnetic susceptibility and the Mossbauer effect data indicate the existence of clusters of iron atoms below 6.5 K.

Magnetic order in RAgGe (R=Gd–Er) intermetallic compounds

Abstract Polycrystalline samples of the ternary intermetallics RAgGe (R=Tb–Er) were investigated by means of magnetization and neutron diffraction measurements. For GdAgGe compounds only magnetic measurements were performed. They crystallize in the hexagonal ZrNiAl-type structure. Magnetic measurements show antiferromagnetic ordering at Neel temperatures between 15.6 K for R–Gd and 3.6 K for R=Er. For TbAgGe the neutron diffraction data reveal a complicated sine modulated magnetic structure which is affected by temperature changes. For DyAgGe and HoAgGe the square modulated magnetic ordering is described by the wave vector k =( 1 3 1 3 0) while for ErAgGe by k =( 1 2 1 2 0). With increasing number of 4f-electrons one observes a change of the direction of magnetic moment from parallel to the c -axis for R=Tb via one which forms an angle ϕ with the c -axis for R=Dy, to one which lies in the basal plane for R=Ho and Er.