Fig. 5: Temperature dependent magnetic state of pure and oxidised nanoparticles.
From: Absence of a pressure gap and atomistic mechanism of the oxidation of pure Co nanoparticles
a–c X-ray absorption (XA) spectra of Co nanoparticles at states A, B, and C (black lines; dashed red lines are fits to the data). d, g X-ray photoemission electron microscopy (XPEEM) Co elemental map and x-ray magnetic circular dichroism (XMCD) contrast map of the nanoparticles at 300 K in state A. e, h XMCD contrast maps of the nanoparticles upon oxidation to state B at 300 K and at 114 K and f, i in state C at 300 K and at 114 K. The scale bar in d is 1 μm. The XMCD contrast in e–i ranges from ±0.020. The XA spectral analysis yields a composition of Co (92 ± 5%), CoO (5 ± 3%), w-CoO (3 ± 3%), and Co3O4(0 ± 2%) for the sample in state A, Co (50 ± 3%), CoO (44 ± 3%), w-CoO (1 ± 3%), and Co3O4(5 ± 2%) in state B, and Co (27 ± 3%), CoO (34 ± 2%), w-CoO (1 ± 3%), and Co3O4(38 ± 2%) in state C.
