RESIDUAL SHORT-RANGE ORDER IN A HEAVY FERMION COMPOUND CeInCu₂. Isao Takahashi, Tomoko Kagayama⁺, Gendo Oomi⁺, Yoshichika Onuki⁺⁺, and Takemi Komatsubara⁺⁺⁺, School of Science, Kwansei Gakuin University Uegahara, Nishinomiya 662, Japan, ⁺Department of Physics, Kumamoto University, Kumamoto 860, Japan, ⁺⁺Department of Physics, Osaka University, Toyonaka 560, Japan, ⁺⁺⁺Department of Physics, Touhoku University, Sendai 980, Japan

CeInCu₂ is a heavy fermion compound which is known to have a cubic, Heusler-type structure. Disorder between Ce and In sites has been investigated by an X-ray diffuse scattering measurement with use of synchrotron radiation (beam line 4C, Photon factory, KEK Japan). Rod-shaped diffuse scattering emanating from the 002 Bragg point along [111] and other equivalent directions in reciprocal space was clearly observed at room temperature. The diffuse scattering is an evidence of residual short-range order which would be an origin of the large residual resistivity and a small T²-term in the resistivity.

In the present study, an analysis of the diffuse scattering has been performed under the assumption of structural disorder in a linear -Ce-In-Ce-In- chain along the [111] direction. For the Ce-site next to the disordered In-site, i.e. Ce atom occupied, obtained order parameters indicate more than 85% occupancy by In atom. In addition, such a disordered cluster tends to form a one-dimensional lattice with an approximate period of 5 - 6 nm. The relationship between the disorder and the large resistivity will be discussed in detail.