2 research outputs found
Magnetic field induced dehybridization of the electromagnons in multiferroic TbMnO3
We have studied the impact of the magnetic field on the electromagnon
excitations in TbMnO3 crystal. Applying magnetic field along the c axis, we
show that the electromagnons transform into pure antiferromagnetic modes,
losing their polar character. Entering in the paraelectric phase, we are able
to track the spectral weight transfer from the electromagnons to the magnon
excitations and we discuss the magnetic excitations underlying the
electromagnons. We also point out the phonons involved in the phase transition
process. This reveals that the Mn-O distance plays a key role in understanding
the ferroelectricity and the polar character of the electromagnons. Magnetic
field measurements along the b axis allow us to detect a new electromagnon
resonance in agreement with a Heisenberg model
Dynamical Multiferroicity
An appealing mechanism for inducing multiferroicity in materials is the
generation of electric polarization by a spatially varying magnetization that
is coupled to the lattice through the spin-orbit interaction. Here we describe
the reciprocal effect, in which a time-dependent electric polarization induces
magnetization even in materials with no existing spin structure. We develop a
formalism for this dynamical multiferroic effect in the case for which the
polarization derives from optical phonons, and compute the strength of the
phonon Zeeman effect, which is the solid-state equivalent of the
well-established vibrational Zeeman effect in molecules, using density
functional theory. We further show that a recently observed behavior -- the
resonant excitation of a magnon by optically driven phonons -- is described by
the formalism. Finally, we discuss examples of scenarios that are not driven by
lattice dynamics and interpret the excitation of Dzyaloshinskii-Moriya-type
electromagnons and the inverse Faraday effect from the viewpoint of dynamical
multiferroicity