THE STRUCTURE INVESTIGATION OF Ce_{1-x}U_{x}Ru_{2}Si_{2}

V. Kavecanský, M. Mihalik, S. Matas

Institute of Experimental Physics, Slovak Academy of Sciences, Watson Str.47, 04353 Kosice, Slovak Republic

Ternary heavy fermion compounds CeRu_{2}Si_{2} and URu_{2}Si_{2} are a subject of scientific examination especially due to their interesting low--temperature properties.

CeRu_{2}Si_{2} exhibits neither magnetic nor superconducting ordering, but pronounced antiferromagnetic correlation was found at low temperatures. URu_{2}Si_{2} exhibits two electronic phase transitions:

a superconducting transition at T_{C}=1.5K and
a second order BCS transition at T_{N}=17.5K, which is associated with weak antiferromagnetic ordering [1].

The interesting magnetic properties are in close connection with the crystal structure of these compounds. The structure investigation was performed on wide concentration range between CeRu_{2}Si_{2} and URu_{2}Si_{2} using X-ray diffraction methods.

Polycrystalline samples Ce_{1-x}U_{x}Ru_{2}Si_ {2}} (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) were prepared by arc-melting. X-ray diffraction on powdered samples did not reveal the presence of any minority phase. The crystal structure parameters were refined by the Rietveld method [2]. Each sample was found to adopt the tetragonal ThCe_{2}Si_{2} type structure (space group I4/mmm). The dependence of the lattice parameters on x confirmed good solubility of U in CeRu_{2}Si_{2} and Ce in URu_{2}Si_{2} in the whole concentration range. Site occupancies of Si atoms were studied by means of detailed investigation of integral intensities. Our analysis of diffraction profiles (using Rietveld refinement and program SHADOW [3] revealed an increase of the Gaussian component of diffraction peaks for all solid solution samples which is mainly associated with increasing of density of microdeformations due to different atom radii of Ce and U.

1. C.Broholm, J.K.Kjems, W.J.L.Buyers, P.Matthews, T.T.M.Palstra, A.A.Menovsky, J.A.Mydosh: Phys.Rev.Letters, 58, (1987), p. 1467
2. Original program DBW3.2 (R.A.Young, D.B.Wiles: J.Appl.Cryst.,15, (1980), p.430 modified by S.A.Howard (1989)
3. S.Howard, R.L.Snyder: Advances in Materials Characterization~II, Material Science Research 19, edited by R.L.Snyder, R.A.Condrate,Sr., and P.F.Johnson (Plenum Press, New York, 1985), p.57-71