Effect of Strain and Dimensionality on the Properties of Manganites

Speaker: 
Carolina Adamo (Dep't of Materials Science and Eng., Cornell Universityi)
Event Date and Time: 
Thu, 2012-02-09 14:00 - 15:00
Location: 
Hennings 318
Local Contact: 
Andrea Damascelli
Intended Audience: 
Graduate

Strain and dimensional confinement can be used to tune magnetic and ferroelectric properties or enhance device performance. In epitaxial films, the different lattice spacing of an underlying substrate can be used to impose a biaxial strain. We have studied the effect of the substrate-induced biaxial strain on the electrical conductivity and magnetic properties of manganite compounds. Epitaxial (001) La0.7Sr0.3MnO3 thin films have been grown by reactive molecular-beam epitaxy (MBE) on single crystalline substrates, varying the substrate-induced biaxial strain from −2.3% to +3.2%. The strain caused the Curie temperature to decrease by up to 100 K in very good agreement with the predictions of Millis et al. [A. J. Millis, T. Darling, and A. Migliori, J. Appl. Phys. 83, 1588 (1998)]. The effect of dimensional confinement on manganites was also investigated in thin films by synthesizing (SrMnO3)n /(LaMnO3)2n superlattices grown by molecular-beam epitaxy on 100 SrTiO3 with periodicities n = 1, 2, 3, 4, 5, 6, 8, and 16. Although the superlattice constituents, LaMnO3 and SrMnO3, are both antiferromagnetic insulators, for small n (n<2) the superlattices behave like the ferromagnetic conductor La0.7Sr0.3MnO3. As n increases, the magnetic properties become dominated by the LaMnO3 layers, but the electronic transport properties continue to be controlled by the interfaces. Angle-resolved photoelectron spectroscopy (ARPES) measurements will be also presented.

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