Dresden 2006 – wissenschaftliches Programm
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MA: Magnetismus
MA 11: Spin-Structures and Magnetic Phase Transitions II
MA 11.6: Vortrag
Montag, 27. März 2006, 16:15–16:30, HSZ 403
Domain imaging and symmetry reduction in LiNiPO4 — •Bas B. van Aken, Takuya Satoh, and Manfred Fiebig — Max-Born-Institut, Max-Born-Straße 2a, 12489 Berlin
Second harmonic generation (SHG) has been applied to study the magnetic symmetry and domain structure of magnetoelectric LiNiPO4. Up to now a simple collinear AFM spin order was assumed. Our SHG data indicate the symmetry is lower. The lower symmetry allows the presence of additional types of domains and toroidal ordering. The lower symmetry is confirmed by the dependence of the domain structure on the magnetic field. Without field AFM plate-like domains are observed. Field cooling leads to a single domain state, which is not allowed by the simple magnetic model. Measuring the magnetic field - temperature phase diagram reveals a first order phase transition to an incommensurate phase. In a magnetic field this transition temperature is reduced, indicating that the magnetic field stabilises the incommensurate phase, which is unusual.