Strain Effects

The CMR manganites are sensitive to all types of perturbations. In particular, it has been shown in bulk that the internal (through the average size of the A-site cation) or external pressure (via hydrostatic pressure) can strongly influence the magnetotransport properties. Since the beginning of the rediscovery of the CMR effect in Mn-based compounds, many studies have been focussed on the strains in thin films. This is due to the fact that Mn electrons, which determine most of the physical properties, are coupled to the lattice degrees of freedom through the Jahn-Teller triva-lent manganese. Thus, strains affect the properties of the manganite thin films, and, in consequence, one needs to correctly understand the effects in order to obtain the desired properties. The following section will discuss the two types of strains: in-the-plane (i.e., substrate-induced strains, Section 3.1) and out-of-plane strain (i.e., thickness dependence, Section 3.2).

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