Berlin 2015 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 23: Magnetic Heuslers, Half-Metals, Semiconductors, and Oxides (organized by MA)

TT 23.13: Vortrag

Montag, 16. März 2015, 18:15–18:30, H 1012

Neutron scattering studies of the field-induced magnetic phases of the Helimagnetic Spinel compound ZnCr₂Se₄. — •Alistair Cameron¹, Dmytro Inosov¹, Pavlo Portnichenko¹, Maksym Surmach¹, and Vladimir Tsurkan² — ¹Institut für Festkörperphysik, Technische Universität Dresden, 01069 Dresden — ²Universität Augsburg, 16135 Augsburg

ZnCr₂Se₄ is a magnetoelectric compound with a cubic spinel (m3m) structure. Magnetic materials with a spinel structure present a strong opportunity to study the interplay between spin, charge and orbital degrees of freedom in a topologically frustrated environment. Particularly, those exhibiting magnetoelectric effects are of particular interest. In zero applied field, the Cr³⁺ S=3/2 moments form an incommensurate magnetic ground state with a screw structure along the (001) direction with a T_N of 20 K, which transforms into a spin spiral state in a magnetic field.

We have performed small angle neutron scattering (SANS) measurements on this spin structure for fields applied along the (100) and (110) directions. We find a field and temperature dependent structure for both field directions, with the reciprocal space propagation vector decreasing with increasing temperature and applied field, and showing a sharp jump in propagation vector across the domain selection transition. The phase diagram deduced by SANS for both field directions appear identical. In addition to investigating the AFM phase, we also probed the proposed spin nematic phase observing no SANS signal in this state, suggesting a lack of long range order.