Sebastian C. Peter

Neutron diffraction studies on structural and magnetic properties of RE2NiGe3 (RE=La, Ce)

Wed, 01 Jan 2014 00:00:00 GMT

Neutron diffraction studies on structural and magnetic properties of RE2NiGe3 (RE=La, Ce) Kalsi, Deepti; Rayaprol, S.; Siruguri, V.; Peter, Sebastian C. We report the crystallographic properties of RE(2)NiG(e)3 (RE=La, Ce) synthesized by arc melting. Rietveld refinement on the powder neutron diffraction (ND) data suggest both compounds are isostructural and crystallize in the non-centrosymmetric Er2RhSi3 type structure having hexagonal space group P2c. In the crystal structure of RE2NiGe3, two dimensional arrangements of nickel and germanium atoms lead to the formation of hexagonal layers with rare earth atoms sandwiched between them. Magnetic susceptibility measurements performed in low fields exhibit antiferromagnetic ordering in cerium compound around (To=) 3.2 K. Neutron diffraction measurements at 2.8 K (i.e., at T< To) neither show any change in the intensities of the diffraction lines nor indicate the appearance of any new diffraction lines in the Q-range of 0.47-7.34 A(-1), thus ruling out any long-range magnetic order. (C) 2014 Elsevier Inc. All rights reserved. Restricted Access

TbRhSn and DyRhSn - Detailed magnetic and Sn-119 Mossbauer spectroscopic studies

Wed, 01 Jan 2014 00:00:00 GMT

TbRhSn and DyRhSn - Detailed magnetic and Sn-119 Mossbauer spectroscopic studies Gurgul, Jacek; Latka, Kazimierz; Pacyna, Andrzej W.; Peter, Sebastian C.; Poettgen, Rainer The results of magnetic studies and Mossbauer spectroscopic investigations are reported for the stannides TbRhSn and DyRhSn crystallizing in the hexagonal ZrNiAl-type structure. The polycrystalline samples of these ternary intermetallics were synthesized by arc melting from metallic precursors. Detailed Sn-119 Mossbauer spectroscopic studies are used to investigate the hyperfine interactions and their temperature evolutions at places occupied by the diamagnetic tin nuclei. Magnetic properties of DyRhSn and TbRhSn were studied by AC/DC magnetometry in a wide temperature range. The results show that both compounds are magnetically ordered at low temperatures. DyRhSn is a non-collinear antiferromagnet with the Neel temperature T-N = 7.5 K, whereas TbRhSn undergoes a transition from a paramagnetic to an antiferromagnetic state at T-N = 20.2 K. An additional transition at T-SR = 10.3 K is detected for TbRhSn which corresponds to some changes in the magnetic moments ordering. The role of the magnetostriction effect in the evolution of the hyperfine parameters and its influence on the observed TbRhSn Mossbauer spectra is discussed. Triangular-like antiferromagnetic arrangements with rare-earth magnetic moments lying in the hexagonal plane are proposed for both compounds at very low temperatures. (C) 2013 Elsevier Ltd. All rights reserved. Restricted Access

Flux Growth of Yb6.6Ir6Sn16 Having Mixed-Valent Ytterbium

Wed, 01 Jan 2014 00:00:00 GMT

Flux Growth of Yb6.6Ir6Sn16 Having Mixed-Valent Ytterbium Peter, Sebastian C.; Subbarao, Udumula; Rayaprol, Sudhindra; Martin, Joshua B.; Balasubramanian, Mahalingarn; Malliakas, Christos D.; Kanatzidis, Mercouri G. The compound Yb6.6Ir6Sn16 was obtained as single crystals in high yield from the reaction of Yb with Ir and Sn run in excess indium. Single-crystal X-ray diffraction analysis shows that Yb6.6Ir6Sn16 crystallizes in the tetragonal space group P42/nmc with a = b = 9.7105(7) angstrom and c = 13.7183(11) angstrom. The crystal structure is composed of a [Ir6Sn16] polyanionic network with cages in which the Yb atoms are embedded. The Yb sublattice features extensive vacancies on one crystallographic site. Magnetic susceptibility measurements on single crystals indicate Curie-Weiss law behavior <100 K with no magnetic ordering down to 2 K. The magnetic moment within the linear region (<100 K) is 3.21 mu(B)/Yb, which is similar to 70% of the expected value for a free Yb3+ ion suggesting the presence of mixed-valent ytterbium atoms. X-ray absorption near edge spectroscopy confirms that Yb6.6Ir6Sn16 exhibits mixed valence. Resistivity and heat capacity measurements for Yb6.6Ir6Sn16 indicate non-Fermi liquid metallic behavior. Restricted Access

Structural and magnetic properties in the polymorphs of CeRh0.5Ge1.5

Wed, 01 Jan 2014 00:00:00 GMT

Structural and magnetic properties in the polymorphs of CeRh0.5Ge1.5 Kalsi, Deepti; Subbarao, Udumula; Rayaprol, Sudhindra; Peter, Sebastian C. We investigate the structural and magnetic properties in the polymorphs of a new compound CeRh0.5Ge1.5. Depending upon the starting materials, and the slightly different synthesis method, we find that CeRh0.5Ge1.5 compound exists in two different space groups. The first compound, alpha-CeRh0.5Ge1.5 crystallizes in tetragonal alpha-ThSi2 structure type in space group I4(1)/amd with lattice parameters, a=4.2034(6) angstrom and c=14.770(3) angstrom. In this structure, the cerium atoms occupy the position between the Rh/Ge tetrahedral layers. On the other hand, the second compound, namely beta-CeRh0.5Ge1.5 crystallizes in the AlB2 type hexagonal structure in space group P6/mmm, with lattice parameters, a=4.2615(7) A and c=4.1813(9) angstrom. The crystal structure of beta-CeRh0.5Ge1.5 consists of two dimensional Rh/Ge hexagonal units and the cerium atoms are sandwiched between them. Magnetization studies exhibit magnetic ordering, as evident from a sharp peak in the plot of magnetic susceptibility measured as a function of temperature in a fixed magnetic field, in alpha-CeRh0.5Ge1.5 and beta-CeRh0.5Ge1.5 at 3.6 K and 12 K, respectively. Structural and magnetic properties of both compounds are presented and discussed here. (C) 2014 Elsevier Inc. All rights reserved. Restricted Access