Its ground state is NM without being strained. LCO is a member of the La xSr xCoO 3 (LSCO) family. Based on a delicately designed device, the authors showed that the ferromagnetic-nonmagnetic (FM-NM) transition repeats while cycling a gating field across the LCO/SrTiO 3 film. This is the case demonstrated in a recent work by Hu et al 18. Therefore, if a technique that triggers lattice strain among different states can be found, the magnetic moment of LCO will be readily switched between definite values. The population of the HS Co 3+ ions can also be tuned by tuning lattice strain and a moment jump from 0 to ~0.8 μ B/Co can be realized by applying an in-plane tensile stress to LCO 11. It was recently found that the Co 3+ ions will take the HS state under tensile strains otherwise the LS state 10, 11, 12. In addition to thermal energy, lattice strain also strongly affects the spin state of LCO 10, 11, 12, 13, 14, 15, 16, 17. With the increase of temperature, as well documented in literature, Co 3+ ions which are initially in a low spin state (LS, t 2 g 6 e g 0, S = 0) 3, 4, 5, 6, 7, 8 gradually transit into an intermediate spin state (IS, t 2 g 5 e g 1, S = 1) above 35 K 3, 4, 5, 6, to a IS and a high spin (HS, t 2 g 5 e g 1, S = 2) mixed state above 300 K and to the HS state above 550 K 3, 5. A typical phenomenon observed in LCO is spin state transition. Perovskite cobaltate LaCoO 3 (LCO) is one of such oxides 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. Complex oxides with competitive mechanisms are suitable objects of study for this purpose due to their susceptibility to external stimuli. Spin state manipulation has always been a focus of intensive studies due to its importance for novel effect exploration and information technology.
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