Competing magnetic structures in Er2PdSi3

Michael Loewenhaupt (Dresden, Germany)

R2PdSi3 compounds have been found to exhibit rich magnetic phenomena arising from the interplay between RKKY interaction, crystal electric feld effect, and geometric frustration due to the AlB2 derived hexagonal structure. Er2PdSi3 orders antiferromagnetically at TN = 7 K and undergoes a second (frequency dependent) phase transition at T2 = 2 K [1]. Neutron diffraction measurements at 1.6 K in zero _eld revealed magnetic reections from two unrelated propagation vectors (Tau1 = ( 1/9 ; 1/9 ; 0) and Tau2 = (0.133, 0, 0)) shortly after the sample was cooled from T > TN . Although eventually the ground state (presumably _1) with slightly lower energy dominates, the whole process took longer times than usually expected. This indicates the coexistence and competition of at least two magnetic states which are energetically very close to each other at finite temperatures. Correspondingly the macroscopic magnetic properties of Er2PdSi3 also demonstrated a time dependent behavior (Fig. 1; magnetization after field sweep to 1 T into FM phase and then down to 0.05 T). A clear exponential decay of the magnetization with two relaxation processes (119 s and 1088 s) can be observed. A possible explanation is to relate the faster process to the restoration of the AFM order either with propagation vector Tau1 or Tau2 from the induced FM state. Afterwards the system slowly settles to the real ground state corresponding to the slower relaxation process. In this contribution detailed time-, temperature- and _eld-dependent neutron scattering results will be compared to the macroscopic properties of Er2PdSi3.

[1] M. Frontzek et al., J. Phys.: Condens. Matter 19, 145276 (2007).

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