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MA: Fachverband Magnetismus

MA 18: Multiferroics and magnetoelectrics I (joint session MA/KFM)

MA 18.9: Vortrag

Dienstag, 13. März 2018, 11:45–12:00, EB 202

Ferrimagnetic-type in-gap spin excitations and magnetoelastic coupling in α-Cu₂V₂O₇ — •Johannes Werner¹, Liran Wang¹, Alexander Ottmann¹, Robin Weis¹, Mahmoud Abdel-Hafiez², Jhuma Sannigrahi³, Souradip Majumdar⁴, Changhyun Koo¹, and Rüdiger Klingeler¹ — ¹Kirchhoff Institute for Physics, Heidelberg, Germany — ²Physikalisches Institut, Goethe-Universität, Frankfurt a.M., Germany — ³ISIS Facility, Rutherford Appleton Laboratory, Didcot, United Kingdom — ⁴Department of Solid State Physics, Kolkata, India

Low-energy magnetic excitations and magnetoelastic coupling in multiferroic α-Cu₂V₂O₇ have been investigated by high-frequency electron spin resonance (HF-ESR) , thermal expansion, magnetostriction, specific heat and magnetisation studies in magnetic fields up to 15 T. Despite a large antiferromagnetic gap, below 100 GHz we observe low-energy magnetic excitations in the spin ordered phase indicating a ferrimagnetic-type resonance branch associated with the Dzyaloshinsii-Moriya-type canted magnetic moment. The anisotropy parameter D=1.3(1) meV indicates a sizeable ratio of DM-exchange and magnetic anisotropy. Dilatometry results show negative thermal expansion at T ≤ 200 K. Pronounced anomalies at T_N=35 K imply coupling to the structure. Failure of Grüneisen scaling confirm that several ordering phenomena are concomitantly driving the multiferroic order. Low-field magnetostriction displays a similar hysteresis loop as the magnetisation which supports the scenario of exchange-striction driven multiferroicity.