CENTRO DE QUIMICA INORGANICA "DR. PEDRO J. AYMONINO"
Unidad Ejecutora - UE
congresos y reuniones científicas
Magnetoelectric orthorhombic and multiferroic hexagonal ErMnO3: THz hybrid modes in RMnO3(R)= Nd, Er, Tm)
NESTOR E. MASSA; V. TA PHUOC ; L. DEL CAMPO; D. DE SOUSA MENESES; P. ECHEGUT; K. HOLLDACK,; M.J. MARTÍNEZ-LOPE; J.A. ALONSO
Denver, CO, USA
Congreso; American Physical Society March Meeting; 2014
American Physical Society
We report on far- and mid-infrared emission, reflection, and transmission spectra of metastable orthorhombic perovskite (Pbnm-TN ∼ 42 K) and hexagonal (P63cm- TN ∼ 84 K) ErMnO3. The number of phonon modes remains constant from 300 K to 4 K. Magnetically disordered electrons in fluctuating orbitals lead to an ambient THz broad reflectivity band. On cooling toward TN the electrons exhibit increasing charge and magnetic short-range correlations and condense into soft bands that harden at about TN as magnetic order sets in. However, at difference of NdMnO3 and TmMnO3 that show correlation with a gap opening in transverse acoustical phonon dispersion and spin order, hexagonal ErMnO3 develops at 5 K a set of four strong hybridized modes centered ∼ 70 cm−1 in addition to one peaking at ∼ 96 cm−1 and another weaker at ∼ 44 cm−1. Orthorhombic ErMnO3 develops a 46 cm−1 band and a very strong one at 91cm−1that seems to correlate to a weaker 98 cm−1 phonon in the short-range only magnetic order environment. We conclude that Er3+ paramagnetic fluctuations increases Mn spins frustration in both compounds being the disruption strongest in orthorhombic ErMnO3 where the THz band and short range magnetic onset may be traced even at 150 K, probably, due to the increment in the Jahn-Teller distortion.