Specific heat and magnetization studies of Fe3−xCoxO4 and Fe3−yO4 single crystals in the neighbourhood of the Verwey transition

To test our previous conclusions about the appearance of two separate peaks in the neighbourhood of the Verwey transition in single-crystal magnetite, we have measured the specific heat and magnetization around the Verwey transition of Fe3-x CoxO4, and Fe3-yO4 single crystals. Our present results confirm our previous conclusions: for Fe3-xCo4O4 with 0 ≤ X ≤ 0·04, two transitions appear in the vicinity of the Verwey transition, and, for Fe3-yO4 with y ≥ 0·037 no transition is observed. The driving forces for the two anomalies are not connected.