Anomalous high-pressure Jahn-Teller behavior in CuWO4.
High-pressure optical-absorption measurements performed in CuWO(4) up to 20 GPa provide experimental evidence of the persistence of the Jahn-Teller (JT) distortion in the whole pressure range both in the low-pressure triclinic and in the high-pressure monoclinic phase. The electron-lattice couplings associated with the e(g)(E⊗e) and t(2g)(T⊗e) orbitals of Cu(2+) in CuWO(4) are obtained from correlations between the JT distortion of the CuO(6) octahedron and the associated structure of Cu(2+) d-electronic levels. This distortion and its associated JT energy (E(JT)) decrease upon compression in both phases. However, both the distortion and associated E(JT) increase sharply at the phase-transition pressure (P(PT)=9.9 GPa), and we estimate that the JT distortion persists for a wide pressure range not being suppressed up to 37 GPa. These results shed light on the transition mechanism of multiferroic CuWO(4), suggesting that the pressure-induced structural phase transition is a way to minimize the distortive effects associated with the toughness of the JT distortion.
Departamento de Física Aplicada-ICMUV, Universitat de València, Edificio de Investigación, c/ Dr. Moliner 50, 46100 Burjassot, Valencia, Spain. javier.ruiz-fuertes@uv.es
J
J
Ruiz-Fuertes
A
A
Segura
F
F
Rodríguez
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D
Errandonea
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MN
Sanz-Ortiz