We have investigated the structural and magnetic properties of $\mathrm{La}\mathrm{Co}{\mathrm{O}}_3$ nanoparticles prepared by a sol-gel method. A ferromagnetic order with $T_C\sim 85\mathrm{K}$ has been observed in the nanoparticles. The infrared spectra give evidence for a stabilizing of higher spin state and a reduced Jahn-Teller distortion in the nanoparticles with respect to the bulk $\mathrm{La}\mathrm{Co}{\mathrm{O}}_3$, which is consistent with the recent reports in the strained films [Phys. Rev. B 75, 144402 (2007)] and proposed to be the possible origin of the observed ferromagnetic order in $\mathrm{La}\mathrm{Co}{\mathrm{O}}_3$.

• Received 8 May 2007

DOI:https://doi.org/10.1103/PhysRevB.76.172407