Abstract
The thickness-dependent magnetic and electrical transport properties of nearly strain-free La0.7Sr0.3CoO3 (LSCO) films grown on (001)-oriented (LaAlO3)0.3 (Sr2AlTaO6)0.7 substrates were systematically studied. A crossover from ferromagnetic/metallic to non-magnetic/insulating behavior occurs at a critical thickness (∼8 nm) that is significantly smaller than LSCO films under larger strains in reported literature. X-ray absorption measurements revealed that the difference of functional properties at reduced film thicknesses was accompanied by changes in the valence state of Co ions at the film/substrate interface.
Highlights
Such phenomenon is usually discussed in terms of the small energy gap between the t2g and eg orbitals for the Co ions, which subsequently results in spin-state transitions that can be tuned by Sr concentration or thermal energy.[9,10]
This critical thickness increased as the Sr concentration decreased, with a value of 15 nm for La1-xSrxCoO3 (x=0.28) thin films with 1.8% tensile strain
La0.7Sr0.3CoO3 (LSCO) thin films were grown on (001)-oriented (LaAlO3)0.3 (Sr2AlTaO6)0.7 (LSAT) substrates in an effort to explore the thickness dependence of their functional properties with a minimal tensile lattice strain of 0.6%
Summary
Sr-doped lanthanum cobaltites (La1-xSrxCoO3) are the topic of extensive research due to their rich phase diagram of electronic and magnetic properties depending on the Sr doping level, x, as well as their potential application in spintronic devices.[1,2,3] At low doping levels (0 < x < 0.18), bulk La1-xSrxCoO3 displays magneto-electronic phase separation (MEPS) that evolves from a spinglass state to a percolated ferromagnetic (FM) state with increasing Sr concentration.[4,5,6,7,8] In this regime, La1-xSrxCoO3 consists of small clusters of an FM/metallic phase, which originates from the Co3+-O-Co4+ double-exchange mechanism, embedded in an antiferromagnetic/insulating matrix that results from a Co3+-O-Co3+ and Co4+-O-Co4+ superexchange interactions.[3]. Thickness-dependent magnetic and electrical transport properties of epitaxial La0.7Sr0.3CoO3 films
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