Magnetic vortex mobility for hollow Fe3O4 submicron particles studied by a hysteresis scaling technique

We report results of magnetic hysteresis scaling of minor loops for hollow Fe3O4 submicron particles with variable diameter of 400-720 nm. As in the case of bulk ferromagnetic materials, a power-law scaling with an exponent of & SIM;1.5 was found to universally hold true between hysteresis loss and remanence of minor loops, although the magnetization process is significantly different from a bulk ferromagnet where irreversible Bloch wall displacement plays a crucial role. The minor-loop coefficient decreases with inner/outer diameter ratio and is almost independent of temperature above T = 30 K. The behavior of the coefficient indicates that a mobility of a magnetic vortex under magnetic fields increases with increasing a inner/outer diameter ratio of a hollow sphere and is weakly temperature dependent. The results suggest that the coefficient can be a sensitive indicator of the particle geometry for vortex spherical particles.