Correlation between crystallographic superstructure and magnetic structures in Tm2PdSi3 studied by neutron scattering in zero and finite magnetic field

Fei Tang (Technical University-Dresden)

R2PdSi3 (R = rare earth) compounds crystallize in hexagonal AlB2 structure (P 6/mmm) with rare earth ions on Al positions and Pd/Si ions on B positions. A crystallographic superstructure caused by Pd and Si ordering is observed, which is closely related to a generic magnetic structure observed in finite magnetic fields from earlier studies. However, the mechanism leading to the generic magnetic structure is yet not clear although crystal electric field effects are supposed to play an essential role. Neutron diffraction measurements have been performed on a Tm2PdSi3 single crystal on the flat cone diffractometer E2 at HZB. In zero field at 0.4 K (well below T_N = 2 K) a magnetic structure with propagation vector tau = (1/8, 1/8, 1/16) was identified. In addition, extra magnetic satellites have been observed which can only be explained by indexing also from the (nuclear) superstructure reflections. Evolution of the magnetic structures in magnetic fields applied along 001 has been followed up to 4 T. The generic magnetic structure found in other R2PdSi3 (R = Tb, Ho and Er) compounds was also observed in Tm2PdSi3 in finite magnetic fields. Here we will present the neutron diffraction data and discuss the correlation between magnetic structures and the crystallographic superstructure.

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