Phonon activity and intermediate glassy phase of YVO₃

• Autores: Massa, Néstor Emilio; Piamonteze, Cinthia; Tolentino, Hélio C. N.; Alonso, José Antonio; Martínez Lope, María Jesús; Casais, María Teresa
• Año de publicación: 2004
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Ciencias Exactas; phonon activity; temperatures; antiferromagnetism
• Institución: Universidad Nacional de La Plata

We show that in YVO₃ additional hard phonons gradually become zone center infrared active below ∼210 K, verifying that a lattice phase transition takes place at about that temperature. Their gradual increment in intensity between ∼210 and ∼77 K is associated with a "glassy" behavior found in the temperature-dependent V K edge pseudoradial distribution. This translates into an increase in the Debye-Waller factors ascribed to the appearance of V local structural disorder below ∼150 K. Conflicts between various ordering mechanisms in YVO₃ bring up similarities of the intermediate phase to known results in dielectric incommensurate systems, suggesting the formation of commensurate domains below 116 K, the onset temperature of G-type antiferromagnetism. We propose that ∼210 and ∼77 K be understood as the temperatures where the commensurate-incommensurate and incommensurate-commensurate "lock-in" phase transitions take place. We found support for this interpretation in the inverted λ shapes of the measured heat capacity and in the overall temperature dependence of the hard phonons.
Facultad de Ciencias Exactas
Centro de Química Inorgánica