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TT: Fachverband Tiefe Temperaturen

TT 4: CE: Quantum-Critical Phenomena 1

TT 4.6: Talk

Monday, March 14, 2011, 12:00–12:15, HSZ 201

Low-temperarture x-ray powder diffraction in the itinerant antiferromagnet YMn₂ — •Kilian Mittermüller, Saskia Gottlieb-Schönemeyer, Andreas Bauer, and Christian Pfleiderer — Physik Department E21, TU München

The cubic C15 Laves compound YMn₂ displays itinerant antiferromagnetism below a Neel temperature T_N=100 K that is accompanied by a large magnetoelastic expansion of order 5 %. We have set up a Siemens D5000 x-ray powder diffractometer with a pulse tube cryo-cooler for measurements at temperatures down to ∼8 K. We report a detailed investigation of the structural modifications associated with the Neel transition in YMn₂ as inferred from the x-ray powder diffraction. In agreement with previous work the Neel transition is dominated by large changes of the lattice constants. In addition the transition is highly hysteretic possibly related to the presence of local strains in the powder. We will discuss putative evidence for a tetragonal lattice distortion in the antiferromagnetic state and its consequences for competing electronic instabilities such as charge density wave order in YMn₂.