Münster 1999 – scientific programme

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DF: Dielektrische Festkörper

DF 6: Poster

DF 6.12: Poster

Thursday, March 25, 1999, 09:30–12:30, Aula

Uncommon behaviour of the electric field dependence of Second Harmonic Generation in nominally pure and Li-doped Potassium Tantalate — •J. Licher¹, C. auf der Horst¹, S. Kapphan¹, V. Vikhnin², and S. Prosandeyev³ — ¹FB Physik, University of Osnabrück, Barbarastraße 7, D-49069 Osnabrück, Germany — ²Ioffe Institute, 194 021 St. Petersburg, Russia — ³Rostov-Don State University, Rostov-Don, Russia

A Second Harmonic Generation (SHG) study of nominally pure and Li-doped crystals of KTaO₃ under applied electric field E exhibit the following set of anomalies. The SHG signal η of nominally pure KTaO₃ first is proportional to E (η = b E, where b is a coefficient). This dependence leads to conclude a induced polarisation P ∼ √E. The other type of surprising behaviour is connected with a rather high b-value, which becomes even higher in reduced, oxygen deficient crystals. Moreover the b-coefficient increases strongly with increasing Li-doping in KTL in comparison with nominally pure KTaO₃. The linear η ∼ E dependence changes at moderately higher E-fields with a step-like transition to a region where the SHG intensity appears to be saturated with good accuracy. The experimental results can be explained on the basis of a cluster model [1].

[1] V. Vikhnin, S. Prosandeyev, S. Kapphan , to be published (1999)

This work is supported by DFG (SFB 225/C7) and one of us, V. Vikhnin, acknowledges support of DFG (436RUS17/112/98).