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Lattice, magnetic excitations and their coupling in multiferroic materials

Abstract : Multiferroic materials present the rare properties that simultaneously exist magnetic and ferroelectric orders and interaction between them. These features in mutliferroics bring out novel physical phenomena and offer possibilities for new device functions. BiFeO3 and hexagonal RMnO3 are two most investigated multiferroics. In this work, we have studied the lattice and spin excitations in hexagonal RMnO3 single crystals (R=Yb, Y, Ho) and BiFeO3 thin films on different substrates. Our measurements of hexagonal RMnO3 single crystals indicate the coupling of lattice and spin excitations. Moreover, the results clearly show the R-Mn and R-R interplane interaction along c-axis also play an important role in the magnetic structure of h-RMnO3. In the case of BiFeO3 thin films, we have observed that high epitaxial strain can destroy the bulk-like cycloidal modulation and non-collinear orders are stable at low strain. A mixture phase of both magnetic orders is also detected in BiFeO3 thin films. In the lower-strain state, a new cycloidal spin structure with a propagation wavevector along [110] is predicted and experimentally observed. Our findings have profound implications for the implementation of BiFeO3 films in magnonic and spintronic devices. Indeed, our Raman scattering measurements reveal that strain can completely quench high energy magnon modes, offering exciting possibilities for BiFeO3 -based magnonic devices.
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https://hal.archives-ouvertes.fr/tel-01493385
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Submitted on : Tuesday, March 21, 2017 - 2:46:18 PM
Last modification on : Monday, November 9, 2020 - 11:35:07 AM
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  • HAL Id : tel-01493385, version 1

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Jiaji Liu. Lattice, magnetic excitations and their coupling in multiferroic materials. Strongly Correlated Electrons [cond-mat.str-el]. Université Paris 7 – Denis Diderot, 2013. English. ⟨tel-01493385⟩

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