Abstract
The search for materials with strong magnetoelectric coupling has been
intense since interesting properties were discovered in the perovskite
TbMnO3. Among the manganese-based perovskite family (RMnO3), magnetic
and electric orders coexist in the orthorhombic phase of the distorted
perovskite TmMnO3. The antiferromagnetic phase induces ferroelectricity,
leading to type-II multiferroic behavior. Although the
temperature-dependent behavior of the Raman-active phonons of other
members of the orthorhombic RMnO3 family was already reported, little
information about orthorhombic TmMnO3 has been published. In this paper,
bulk samples of orthorhombic TmMnO3 were obtained through HPHT
treatment. Structural and magnetic properties of the synthesized samples
were analyzed for phase confirmation. Temperature-dependent Raman
spectra of bulk orthorhombic TmMnO3 revealed weak spin-phonon coupling
in the incommensurate antiferromagnetic ordered phase around 44 K. Raman
spectra are also sensitive to the magnetic transition from the
incommensurate to E-type antiferromagnetic phase, where the frequency
renormalization due to the spin-phonon coupling vanishes. This feature
shows the existence of an orbital-spin-phonon coupling based on the
magnetic ordering of the low-temperature phase.
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