The bulk magnetite is ferrimagnetic, "generated by parallel alignment of magnetic moments on tetrahedral sites and anti-parallel alignment of ferrous and ferric spins on octahedral sites" . In the Figure by Blaney, we can see a generic ferrimagnetic hysteresis loop, with coercivity and remanence (retentivity). "As particle size is decreased, the amount of exchange-coupled spins resisting spontaneous magnetic reorientation is decreased, tending towards paramagnetic or superparamagnetic magnetization" . As previously told, when the magnetite particle size decreases, the ferrimagnetic behavior is reduced and the superparamagnetic behavior enhanced. Increasing the temperature, the thermal energy facilitates "magnetic reorientation, or superparamagnetic magnetization" (Blaney mentioning Kiely). "In accordance with superparamagnetic behavior, magnetite nanoparticles exhibit zero coercivity and remanence in hysteresis loops as illustrated in Figure [of . Coercivity slowly builds as magnetite particle diameter increases". In the caption of the mentioned figure, it is told that the absence of hysteresis loop is implying superparamagnetism .