Fig. 4
a XRD patterns for pristine Fe3O4 before heating and after heating to 600 K (green), 900 K (red) (black dotted line, experimental data; solid line, fitted; magenta, difference; pars, SG #227 phase) (the small filled squares represent the peaks for the glue used for high-temperature VSM measurements), b enlarge pattern for (220) peak, and c enlarge pattern for (440) peak