We present results on the structural and magnetic properties of highly crystallineα-Fe2O3nanoparticles of average size similar to 200 nm, synthesized from a novel sol-gel method using metal alkoxide precursor. These particles are multi-domain, showing the weak ferromagnetic antiferromagnetic (WF-AF) transition (i. e., the Morin transition) at T-M = 256 (2) K. Mossbauer measurements revealed a jump in hyperfine parameters (HP's) at T similar to T-M, which also displays thermal hysteresis upon cooling or heating the sample. The analysis of HP's as a function of temperature allowed us to discard temperature gradients as well as the coexistence of WF/AF phases as possible origins of this hysteretic behaviour. Instead, the hysteresis can be qualitatively explained by the small size and high-crystallinity of the particles, which hinder the nucleation of the WF or AF phases yielding metastable states beyond T-M.