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Dresden 2006 – scientific programme

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MA: Magnetismus

MA 11: Spin-Structures and Magnetic Phase Transitions II

MA 11.5: Talk

Monday, March 27, 2006, 16:00–16:15, HSZ 403

Frustration in R2PdSi3 (R = Tb, Er): Spin-glass or magnetic short-range order? Neutron diffraction studies — •Matthias Frontzek1, Andreas Kreyssig1, Jens-Uwe Hoffmann2, and Michael Loewenhaupt11TU Dresden, Institut für Festkörperphysik, 01062 Dresden — 2Hahn-Meitner-Institut, 14109 Berlin

The series R2PdSi3 (R = rare earth), crystallizing in an AlB2 derived hexagonal structure, have been found to exhibit strong anisotropic magnetic properties. Below their respective Néel temperatures Tb2PdSi3 (24 K) and Er2PdSi3 (7 K) feature a second phase transition at 7 K and 2 K, respectively. This second transition shows a strong frequency dependence in ac-susceptibility measurements. Several authors assume a spin-glass state below this second phase transition.

We performed neutron diffraction experiments on E2 at HMI Berlin within a temperature range from 0.4 K to 300 K and magnetic fields up to 6.5 T on Tb2PdSi3 and Er2PdSi3 single crystals.

Tb2PdSi3 orders antiferromagnetically at 24 K with a magnetic moment direction in the basal plane and a propagation vector τ = (1/2  1/2  1/16). Furthermore, we observe additional short-range magnetic order (SRO) at low temperatures. The second phase transition is correlated to the temperature dependence of the SRO. The SRO becomes long range ordered when a magnetic field (>1.5 T) is applied.

Er2PdSi3 orders antiferromagnetically at 7 K with a magnetic moment direction along the hexagonal c-axis and a propagation vector τ = (0.11 0.11 0). In this case the second phase transition is correlated to a "squaring up" of the antiferromagnetic structure.

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