For applying tensile or compressive uniaxial strain to functional thin films, we propose a novel approach in combining a piezoelectric-based device and a technical metallic substrate used widely in the 2nd generation coated conductors (i.e. superconducting tapes). A strain-induced shift of the superconducting transition temperature of 0.1 K for Co-doped BaFe 2 As 2 was observed along [100] direction, corresponding to a uniaxial pressure derivative dT c /dp 100 = −4 K/GPa. For Mn 3 CuN, a uniaxial strain derivative along [100] direction of the Curie temperature dT C /d 100 = 13 K/% was observed. The current approach is applicable to various functional thin films in a wide range of temperatures. a)

Epitaxial thin films of Bi 1-x Ba x FeO 3 have been deposited by sputtering on LaAlO 3 and SrTiO 3 substrates with and without conducting buffer layers of paramagnetic LaNiO 3 and ferromagnetic La 0.7 Sr 0.3 MnO 3 , and their structural, magnetic and ferroelectric properties have been investigated. It has been shown from magnetic and ferroelectric characterization that Bi 1-x Ba x FeO 3 epitaxial films in a thickness of 300 nm exhibited reasonable multiferroic properties at room temperature. Spin-filter junctions consisting of a La 0.7 Sr 0.3 MnO 3 / Bi 1-x Ba x FeO 3 /LaNiO 3 epitaxial heterostructure have been fabricated using photolithography and ion milling. The junctions with a Bi 1-x Ba x FeO 3 layer thickness of 4 nm exhibited nonlinear current-voltage (I-V) characteristics with the barrier height of 0.37 eV, and MR effect at 4.2 K, indicating that the Bi 1-x Ba x FeO 3 ultrathin layers serves as ferromagnetic tunnel barriers in spin-filter junctions.

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