On the magnetic characterization and quantification of the superparamagnetic fraction of traffic-related urban airborne PM in Rome, Italy

► We studied the superparamagnetic (SP) fraction of traffic-related PM. ► The SP fraction makes the hysteresis properties at 10 K different from those at 293 K. ► The SP fraction carries a viscous 10-15% of the total saturation remanence. ► The SP fraction is mostly associated to larger multidomain particles.