Reversible Thermal Hysteresis in Heating‐Cooling Cycles of Magnetic Susceptibility: A Fine Particle Effect of Magnetite

Thermomagnetic curves of magnetic susceptibility (κ) are key to characterizing properties. We report hump-shaped κ-T magnetite-bearing basalt during heating-cooling cycles ∼340°C, with a large thermal hysteresis and similar starting ending values, even in multiple repeated cycles, ruling out changes mineralogy. Based on FORC diagrams published results engineered materials, we propose that arises from configurations moments clusters single-domain particles due dipolar coupling, different collective behavior heating cooling. This effect modifies the relaxation individual nanoparticles. indicate an increase effective particle sizes after 700°C-heating. Our warning against premature interpretation decreasing trend by maghemite inversion. Instead, fine should be considered when is detected.