Regensburg 2016 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 19: Magnetic Materials III
MA 19.6: Vortrag
Dienstag, 8. März 2016, 12:45–13:00, H31
Study of the magnetic excitation spectrum of the helimagnetic spinel compound ZnCr2Se4 — •Alistair Cameron1, Yullia Tymoshenko1, Yevhen Onykiienko1, Pavlo Portnichenko1, Helen Walker2, Douglas Abernathy3, and Dmytro Inosov1 — 1Institut für Festkörperphysik, TU Dresden, Germany — 2ISIS Neutron Source, Rutherford Appleton Laboratory, United Kingdom — 3SNS, Oak Ridge National Laboratory, United States
ZnCr2Se4 is a magnetoelectric compound with a cubic spinel (Fd3m) structure. In zero applied field, the Cr3+ S=3/2 moments form an incommensurate magnetic ground state with a screw structure along the [100] direction and a TN of 20 K, which transforms into a spin-spiral state in an applied magnetic field. Above the critical field HC2 this material exhibits a proposed spin-nematic state, before becoming fully ferromagnetic at HC3. Previously, we studied this material with neutron diffraction, and found a temperature- and field-dependent magnetic structure in the spin-spiral phase with no long-range order in the proposed spin-nematic state. Here, we probe the spin-excitation spectrum of ZnCr2Se4 using time-of-flight neutron scattering, which allows us to investigate a large area of momentum space. The relatively short spin-spiral in ZnCr2Se4 leads to a large separation of the nuclear and magnetic Brag peaks in momentum space, making it possible to resolve excitations originating from a single magnetic Bragg peak. We observe two clear branches emanating from the magnetic satellites, an intense low energy mode alongside a steeper, less intense branch at higher energies.