Turning antiferromagnetic Sm0.34Sr0.66MnO3 into a 140 K ferromagnet using a nanocomposite strain tuning approach

Abstract

Ferromagnetic insulating thin films of Sm_0.34Sr_0.66MnO₃ (SSMO) on (001) SrTiO₃ substrates with a T_C of 140 K were formed in self-assembled epitaxial nanocomposite thin films. High T_C ferromagnetism was enabled through vertical epitaxy of the SSMO matrix with embedded, stiff, ∼40 nm Sm₂O₃ nanopillars giving a c/a ratio close to 1 in the SSMO. In contrast, bulk and single phase SSMO films of the same composition have much stronger tetragonal distortion, the bulk having c/a >1 and the films having c/a <1, both of which give rise to antiferromagnetic coupling. The work demonstrates a unique and simple route to creating ferromagnetic insulators for spintronics applications where currently available ferromagnetic insulators are either hard to grow and/or have very low T_C.