Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 3: Correlated Electrons - Heavy Fermions

TT 3.6: Vortrag

Freitag, 4. März 2005, 11:30–11:45, TU H3027

Magnetic structure vs. crystallographic disorder in single crystalline UPt₂Si₂ — •S. Süllow¹, A. Otop¹, A. Loose², J. Klenke², R. Feyerherm², R.W.A. Hendrikx³, and J.A. Mydosh^3,4 — ¹IFP, TU Braunschweig, Braunschweig, Germany — ²BENSC, HMI, Berlin, Germany — ³Leiden University, Leiden, The Netherlands — ⁴MPI-CPfS, Dresden, Germany

We present a detailed investigation of the crystallographic structure, lattice disorder and magnetic order of a single–crystal of the moderately mass–enhanced U intermetallic UPt₂Si₂. Utilizing the bright contrast between U, Pt and Si in neutron scattering, we establish the lattice symmetry to be P4/nmm (CaBe₂Ge₂-lattice). Moreover, the observation of an anomalously large thermal displacement factor U₁₁/U₂₂ for the Pt(2) and Si(2) sites at low temperatures indicates frozen–in disorder on these sites. The material undergoes an antiferromagnetic transition below T_N = 32.1 K, with ferromagnetically coupled a – b –planes and an antiferromagnetic stacking along the c axis. In addition, as result of the crystallographic disorder we observe magnetic clusters up to T_irr = 34 K. The existence of the clusters explains the previously observed anomalous antiferromagnetic domain pinning in the compound [1]. Moreover, the disorder bears relevance to the electronic transport properties of the compound, which are commonly metallic along the a axis, but disorder dominated in c direction.

[1] A. Otop et al., J. Appl. Phys. 95 (2004) 6702