Paramagnetic collective electronic mode and low temperature hybrid modes in the far infrared dynamics of orthorhombic NdMnO₃

We report on the far- and mid-infrared reflectivity of NdMnO₃ from 4 to 300 K. Two main features are distinguished in the infrared spectra: active phonons in agreement with expectations for the orthorhombic D¹⁶<sub>2h</sub>-Pbnm (Z = 4) space group remaining constant down to 4 K and a we...

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Autores principales: Massa, Néstor Emilio, Campo, Leire del, De Sousa Meneses, Domingos, Echegut, Patrick, Martínez-Lope, María Jesús, Alonso, José Antonio
Formato: Articulo
Lenguaje:Inglés
Publicado: 2013
Materias:
Ciencias Exactas
Física
reflectivity
infrared spectra
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/131564
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
id I19-R120-10915-131564
record_format dspace
institution Universidad Nacional de La Plata
institution_str I-19
repository_str R-120
collection SEDICI (UNLP)
language Inglés
topic Ciencias Exactas
Física
reflectivity
infrared spectra
spellingShingle Ciencias Exactas
Física
reflectivity
infrared spectra
Massa, Néstor Emilio
Campo, Leire del
De Sousa Meneses, Domingos
Echegut, Patrick
Martínez-Lope, María Jesús
Alonso, José Antonio
Paramagnetic collective electronic mode and low temperature hybrid modes in the far infrared dynamics of orthorhombic NdMnO₃
topic_facet Ciencias Exactas
Física
reflectivity
infrared spectra
description We report on the far- and mid-infrared reflectivity of NdMnO₃ from 4 to 300 K. Two main features are distinguished in the infrared spectra: active phonons in agreement with expectations for the orthorhombic D¹⁶<sub>2h</sub>-Pbnm (Z = 4) space group remaining constant down to 4 K and a well defined collective excitation in the THz region due to e<sub>g</sub> electrons in a d-orbital fluctuating environment. We trace its origin to the NdMnO₃ high-temperature orbital disordered intermediate phase not being totally dynamically quenched at lower temperatures. This results in minute orbital misalignments that translate into randomized non-static e<sub>g</sub> electrons within orbitals yielding a room-temperature collective excitation. Below T<sub>N</sub> ∼ 78 K, electrons gradually localize, inducing long-range magnetic order as the THz band condenses into two modes that emerge pinned to the A-type antiferromagnetic order. They harden simultaneously down to 4 K, obeying power laws with T<sub>N</sub> as the critical temperature and exponents β ∼ 0.25 and β ∼ 0.53, as for a tri-critical point and Landau magnetic ordering, respectively. At 4 K they match known zone center spin wave modes. The power law dependence is concomitant with a second order transition in which spin modes modulate orbital instabilities in a magnetoelectric hybridized orbital-charge-spin-lattice scenario. We also found that phonon profiles also undergo strong changes at T<sub>N</sub> ∼ 78 K due to magnetoelasticity.
format Articulo
Articulo
author Massa, Néstor Emilio
Campo, Leire del
De Sousa Meneses, Domingos
Echegut, Patrick
Martínez-Lope, María Jesús
Alonso, José Antonio
author_facet Massa, Néstor Emilio
Campo, Leire del
De Sousa Meneses, Domingos
Echegut, Patrick
Martínez-Lope, María Jesús
Alonso, José Antonio
author_sort Massa, Néstor Emilio
title Paramagnetic collective electronic mode and low temperature hybrid modes in the far infrared dynamics of orthorhombic NdMnO₃
title_short Paramagnetic collective electronic mode and low temperature hybrid modes in the far infrared dynamics of orthorhombic NdMnO₃
title_full Paramagnetic collective electronic mode and low temperature hybrid modes in the far infrared dynamics of orthorhombic NdMnO₃
title_fullStr Paramagnetic collective electronic mode and low temperature hybrid modes in the far infrared dynamics of orthorhombic NdMnO₃
title_full_unstemmed Paramagnetic collective electronic mode and low temperature hybrid modes in the far infrared dynamics of orthorhombic NdMnO₃
title_sort paramagnetic collective electronic mode and low temperature hybrid modes in the far infrared dynamics of orthorhombic ndmno₃
publishDate 2013
url http://sedici.unlp.edu.ar/handle/10915/131564
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