Regensburg 2007 – wissenschaftliches Programm

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SYSE: Symposium Strain-Engineering for New Functional Structures

SYSE 2: Strain engineering in ferroics and photonics

SYSE 2.2: Vortrag

Montag, 26. März 2007, 16:45–17:00, H1

Piezoelectric strain control of thin film magnetism — •Kathrin Dörr and Christian Thiele — IFW Dresden, Postfach 270116, Dresden, Germany

Biaxial strain is a most crucial parameter influencing ferroic (ferroelectric, magnetic) properties of oxides. It is, on the other hand, not easily controlled independently of other parameters and in well-defined way. One approach for reversible biaxial strain variation in epitaxial films fitting to a pseudocubic lattice parameter of about 4.0 Angstrom is to utilize a 0.72PMN-0.28PT(001) substrate. The huge, homogeneous and nearly linear inverse piezoelectric strain of PMN-PT(001) allows one to biaxially compress as-grown films by applying electric voltage.

Ferromagnetic films of colossal magnetoresistive manganites La_1−xA_xMnO₃ (A = Sr; Ca) grown epitaxially on PMN-PT(001) have been subject to strain-dependent measurements of magnetization (M) and electrical resistance. For this family of materials, an extraordinary sensitivity towards external parameters (magnetic field, light, pressure) related to multiple phase neighbourhood is known. A pronounced shift of the Curie temperature with the strain is detected, naturally accompanied with strain dependence of M. The magnetoelectric coupling of the film-substrate system reaches a value of α = µ₀ dM/ dE = 6E-8 s/m (with substrate electric field E) at 300 K, revealing efficient strain-mediated coupling of the ferroic components. The observed resistive gauge factors of the films (400) further underline the strong impact of biaxial strain in manganites.