Berlin 2018 – scientific programme
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MA: Fachverband Magnetismus
MA 18: Multiferroics and magnetoelectrics I (joint session MA/KFM)
MA 18.9: Talk
Tuesday, March 13, 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 TN=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.