Figure 8.

Hysteresis loops of FeO/Fe3O4NPs at temperature of 100 K after zero field cooling (ZFC) and field cooling (FC) in magnetic field up to 1 T. Note that the shifted ZFC loop is the result of a coupling effect at the ferromagnetic and anti-ferromagnetic interface

Chen et al. Nanoscale Research Letters 2009 4:1343-1350   doi:10.1007/s11671-009-9403-x