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Photo of Daniel Kronmann

Dr. Martin Diestelhorst

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Research associate in Solid State Physics, Martin-Luther-University Halle-Wittenberg, Department of Physics

Curriculum Vitae

Born August 18th, 1954 in Halle (Saale), Germany
1975-1980 Studies of physics at Martin-Luther-University Halle-Wittenberg, Germany
1980Diploma thesis in solid state physics on "Nonlinear elastic, electromechanical and dielectric properties in the vicinity of structural phase transitions"
1980-1984 Scientific assistant at the Department of Physics, Martin-Luther-University Halle-Wittenberg,
1984 Doctoral thesis in solid state physics on "Nonlinearities of TGS-crystals with defects".
since 1984 Research associate in Solid State Physics at the Department of Physics, Martin-Luther-University Halle-Wittenberg
1985 Dr.rer.nat. degree at Martin-Luther-University Halle-Wittenberg.
1991-1998Member of the Sonderforschungsbereich SFB 185 (Nonlinear Dynamics)
1992-1997 Project leader “Small signal amplification in a nonlinear series resonance circuit with TGS-capacitor near a period-doubling bifurcation” Ministry of Science and Technology (BMBF)
Research interests
Nonlinear dynamics, especially bifurcations and chaos in nonlinear resonators and stochastic resonance; investigation of nonlinear elastic, electromechanical, dielectric and pyroelectric properties of ferroelectrics (bulk materials and thin films) by methods derived from nonlinear dynamics; switching properties of ferroelectrics; phase transitions, especially ferroelectric phase transitions
His Topic of Materials' Days 2009:

Nonlinear Effects in Nanoscaled Ferroelectrics and Possible Applications

Ferroelectrics are materials with a broad field of applications. This follows from the wide variety of their physical properties, including high dielectric permittivity for the application in capacitors, high piezoelectric coefficients for the conversion of mechanical influences into electric signals and vice versa, good pyroelectric properties for application in infrared detectors, electrooptic effects for use in light-modulators or displays, and polarization reversal (switching) caused by external electric fields for the application in ferroelectric memories (FERAMs).
It is well known that most of the properties of ferroelectric materials exhibit nonlinear characteristics. This means the response of the ferroelectric materials is not proportional to the external impact.
These nonlinear effects become more and more important if the external influences like electric field strengths or mechanical stresses are increased. On the other hand the miniaturization of sensors, transducers and other elements produced on the basis of these materials leads to nonlinear effects at external fields that would be considered as moderate from a macroscopic point of view. Often this is considered as a drawback for applications. But sometimes such nonlinear properties can be used as a basis for completely new principles of applications.
We demonstrate this by means of a nonlinear series resonance circuit with ferroelectric capacitor, which can be tuned to chaotic behavior, well known from the theory of nonlinear dynamical systems. A period doubling bifurcation on the route to chaos is used to construct a special sensor combining both linear as nonlinear properties of the ferroelectric detector material.