Berlin 2018 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 100: Frustrated Magnets - Pyrochlore Oxides
TT 100.5: Vortrag
Donnerstag, 15. März 2018, 16:30–16:45, H 3005
Spin dynamics of the ordered dipolar-octupolar pseudospin pyrochlore Nd2Hf2O7 — •Alexandros Samartzis1,2, Jianhui Xu1, Vivek K. Anand1, Nazmul A.T.M. Islam1, Jacques Ollivier3, and Bella Lake1,2 — 1Helmholtz-Zentrum Berlin — 2Technical University Berlin — 3Institut Laue-Langevin, Grenoble, France
The rare earth pyrochlore magnets have been extensively studied during the last decades due to their quintessential lattice for frustration which leads to exotic ground states with strong anisotropy. From this lattice the competition of crystal field, super-exchange and dipolar interactions can result in novel states, such as spin liquid, spin ice etc. The Nd3+ ion, on such a lattice has a Kramers doublet ground state with a ’dipolar-octupolar’ wavefunction leading to a fascinating phase diagram. Here we report first results of inelastic scattering on a new Nd-based pyrochlore, Nd2Hf2O7. Recent macroscopic measurements have revealed an ordered all-in - all-out AFM ground state with slow spin dynamics and a strongly reduced magnetic moment due to local fluctuations. Motivated by these interesting results, we performed low energy Inelastic Neutron scattering on a large single crystal grown by the floating zone technique. The results reveal a long range magnetic order below T=600mK. The excitations form a gapped flat band at energy DE 0.1meV reflecting the pinch-point pattern of a Coulombic phase. Above the flat band, collective dispersive excitations emerge from the pinch points. Linear spin-wave theory was used to determine the exchange parameters (Ja) applied in an appropriate Hamiltonian.