Dresden 2017 – scientific programme

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MA: Fachverband Magnetismus

MA 44: PhD Symposium Quantum Magnets (contributed talks)

MA 44.6: Talk

Wednesday, March 22, 2017, 16:30–16:45, HSZ 403

Pseudo-Goldstone magnons in the Heisenberg helimagnet ZnCr₂Se₄. — •Yuliia Tymoshenko¹, Yevhen Onykiienko¹, Pavlo Portnichenko¹, Alistair Cameron¹, Doug Abernathy², Jacques Ollivier³, Astrid Schneidewind⁴, Vladimir Tsurkan⁵, and Dmytro Inosov¹ — ¹TU Dresden, D-01069 Dresden, Germany — ²ORNL, Oak Ridge, Tennessee 37831, USA — ³ILL, 38042 Grenoble, France — ⁴JCNS, D-85747 Garching, Germany — ⁵University of Augsburg, 86135 Augsburg, Germany

Chromium spinels provide great opportunities to investigate magnetic interactions between classical spins on the almost ideal pyrochlore lattice. ZnCr₂Se₄ is a spinel compound with incommensurate spin-spiral ground state. In this talk we present inelastic neutron scattering measurements of magnetic excitations in ZnCr₂Se₄ over a wide range of energies in the whole Brillouin zone. Comparing our data with spin-dynamical calculations we have extracted exchange parameters up to the fourth nearest neighbour and found a good agreement with the isotropic Heisenberg model. Furthermore, measurements of low-energy helimagnon excitations performed in the single-domain spin spiral state revealed two distinct modes: the Goldstone mode emerging from incommensurate magnetic Bragg peaks and a soft pseudo-Goldstone mode emanating from an orthogonal wave vector.