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Acoustical and related effects in manganite compounds.

Konstantin Dyakonov ¹, Alexander Goltsev ¹, Ludmila Kulakova ¹, Eduard Yakhkind ¹, Vladimir P. Dyakonov ³, Stanislaw J. Lewandowski ³, Henryk Szymczak ³, Yakov M. Mukovskii ²

1. Ioffe Physico-Technical Institute (Ioffe), Polytechnicheskaya, 26, Saint-Petersburg 194021, Russian Federation
2. Moscow State Steal & Alloys Institute, Moscow 117936, Russian Federation
3. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland

Abstract

The studies of manganites have shown that strong electron-phonon interaction plays important role in the formation of CMR effect discovered in these compounds. Due to electron-phonon interaction acoustical techniques are sensitive tools for investigations of transport and structural properties of manganites.
In this report we present studies of the surface acoustic wave (SAW) attenuation and the acoustoelectric (AE) effect in the La_0.67Ca_0.33MnO₃ (LCMO) film. We measured the SAW attenuation at 30 MHz, and at higher harmonics of this frequency. The attenuation reaches a maximum at the temperature corresponding to the peak of the film resistivity, and increases with increasing SAW frequency. The applied magnetic field reduces the attenuation. The observed behavior in the paramagnetic state of the LCMO film is in a good agreement with the relaxation type theory of the sound attenuation in conducting film. Frequency dependence of the SAW attenuation gives evidence for the linear dependence of the conductivity which probably points to a significant role of the spin disorder in the electronic transport in manganites.
The investigations of the AE effect produced by the SAW in the LCMO film have
revealed an anomalous (even in the SAW direction of propagation) contribution to the acoustoelectric current, which coexists with the ordinary (odd) effect. The anomalous effect appears to depend on strong modulation of the film conductivity resulting from elastic deformations carried by the SAW. The magnetic field increases the magnitude of the anomalous AE effect while the ordinary effect is left essentially unchanged. The measurements with the SAW split into two components, propagating in the LCMO film in opposite directions, result in cancellation of the ordinary AE effect and augmentation of the anomalous one, thus confirming our understanding of the anomalous AE effect in manganites.

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Acoustical and related effects in manganite compounds.

Presentation: invited oral at E-MRS Fall Meeting 2003, Symposium D, by Konstantin Dyakonov See On-line Journal of E-MRS Fall Meeting 2003 Submitted: 2003-05-23 14:30 Revised: 2009-06-08 12:55

Presentation: invited oral at E-MRS Fall Meeting 2003, Symposium D, by Konstantin Dyakonov
See On-line Journal of E-MRS Fall Meeting 2003

Submitted: 2003-05-23 14:30 Revised: 2009-06-08 12:55