Spin-state configuration induced faster spin dynamics in epitaxial La1−xSrxCoO3 thin films

• Highly epitaxial structural La1-xSrxCoO3 thin films were preparated using magnetron sputtering method.
• Contact angle in a glass pore differs from contact angle on a flat glass surface.
• HS-Co3+ and LS-Co4+ is the most stable spin-state configuration for LaSrCoO at ground state
• The faster spin dynamics observed in LaSrCoO has a close relationship with the higher-spin Co3+.
• The smaller FM cluster sizes (~2.16 to ~21.5 nm) in LaSrCoO thin films result in faster spin dynamics (τ0 ~ 10-15 s).

Two important features: spin-state configuration and spin dynamics in phase-separated ferromagnetic/spin-glass epitaxial La1−xSrxCoO3 thin films (x=0.07, 0.17, 0.26, 0.30, 0.40, 0.60) have been investigated and elaborated, proved by both magnetic analyses and first principle calculations. The configuration with high-spin (HS) state Co3+ and low-spin (LS) state Co4+ is considered to be the most stable spin-state configuration for La1−xSrxCoO3 at ground state, which was demonstrated by calculating the magnetic moments of La1−xSrxCoO3, as well as first principle calculation. The stretched Co–O bond by Sr doping causes the decrease of crystal field splitting, resulting in the HS state Co3+ and LS state Co4+. The spin dynamics in the La1−xSrxCoO3 thin films was found to be faster than the classic spin-glass compounds, which is attributed to the higher-spin Co3+, and rather smaller ferromagnetic cluster size (~2.16 to ~21.5 nm) in the epitaxial films than that in referenced polycrystalline compounds (~35 to ~240 nm).