Magnetic and hysteretic properties of Fe-filled nanotubes

The hysteretic properties of Fe-filled carbon nanotubes samples are presented and related to their magnetic phase distribution obtained by Mossbauer spectroscopy. The most relevant result corresponds to the observation of a high anisotropy gamma -Fe phase, getting magnetically ordered at 100 K. Below this temperature, irreversibility in the high field zero field cooling (ZFC)-field cooling (FC) curves, as well as shifted hysteresis loops are observed. These results are explained in terms of the blocking of the high anisotropy phase and the development of exchange anisotropy.