Strain-induced spin states in atomically ordered cobaltites.
Epitaxial strain imposed in complex oxide thin films by heteroepitaxy is recognized as a powerful tool for identifying new properties and exploring the vast potential of materials performance. A particular example is LaCoO(3), a zero spin, nonmagnetic material in the bulk, whose strong ferromagnetism in a thin film remains enigmatic despite a decade of intense research. Here, we use scanning transmission electron microscopy complemented by X-ray and optical spectroscopy to study LaCoO(3) epitaxial thin films under different strain states. We observed an unconventional strain relaxation behavior resulting in stripe-like, lattice modulated patterns, which did not involve uncontrolled misfit dislocations or other defects. The modulation entails the formation of ferromagnetically ordered sheets comprising intermediate or high spin Co(3+), thus offering an unambiguous description for the exotic magnetism found in epitaxially strained LaCoO(3) films. This observation provides a novel route to tailoring the electronic and magnetic properties of functional oxide heterostructures.
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
Woo Seok
WS
Choi
Ji-Hwan
JH
Kwon
Hyoungjeen
H
Jeen
Jorge E
JE
Hamann-Borrero
Abdullah
A
Radi
Sebastian
S
Macke
Ronny
R
Sutarto
Feizhou
F
He
George A
GA
Sawatzky
Vladimir
V
Hinkov
Miyoung
M
Kim
Ho Nyung
HN
Lee
D003035:Cobalt / Q000737:chemistry*; D055119:Elastic Modulus; D007811:Lanthanum / Q000737:chemistry*; D060526:Magnetic Fields; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D010087:Oxides / Q000737:chemistry*; D010316:Particle Size
D010087:Oxides; D003035:Cobalt; D007811:Lanthanum; C060728:cobalt oxide