Reversible thermal hysteresis in heating-cooling cycles of magnetic susceptibility

Thermomagnetic curves of magnetic susceptibility are key to characterizing magnetic properties. The ~300-400°C decreasing trend is usually attributed to the inversion of maghemite to hematite. We present thermomagnetic curves of magnetic susceptibility, together with first-order reversal curves of natural basalt and red soil samples. Our results offer a new explanation of a marked drop in thermomagnetic curves at ~300-400°C, that single-domain magnetite undergoing the SSD to SP transition should be considered. For plotting thermomagnetic curves and generating first-order reversal diagrams, all data is available on the data sites.