Antiparallel state, compensation point, and magnetic phase diagram of Fe3O4/Mn3O4 superlattices -: art. no. 094421

The magnetic response of a ferrimagnetic/ferrimagnetic superlattice, [Fe3O4 (20 Angstrom)/Mn3O4 (80 Angstrom)](x20), is measured as a function of external field (-50-50 kOe) and temperature (5-300 K). A compensation point (T-cp) is identified similar to 33 K at which the remanence changes sign and low-field M-T curves show minima, indicating that the net moments of Fe3O4 and Mn3O4 are antiparallel. At temperatures >similar to 50 K, the magnetic response becomes pure Fe3O4-like. Detailed M-H curves (at T<50 K) further exhibit magnetic phase transition at higher external field. As H is above H*<similar to>10 kOe, the magnetization is enhanced and then saturates at H similar to 40 kOe. These phases are similar to the twisted phases, originating from a competition between Zeeman and exchange energies, previously observed in antiparallel metallic multilayers. A H-T magnetic phase diagram of the present superlattice is presented and five phases are included: the Mn3O4-aligned, Fe3O4-aligned, twisted, ferrimagnetic saturated, and pure Fe3O4 phases; M-H curves also show asymmetry at temperatures below and above T-cp, which is probably related to the anisotropy effect of Mn3O4 (tetragonal structure). The fundamental mechanism of the antiparallel coupling between Mn3O4 and Fe3O4 is also discussed.