Anomalous magnetic anisotropy in Mn$_{3}$O$_{4}$ investigated by $^{55}$Mn$^{2+}$ and $^{55}$Mn$^{3+}$ Nuclear magnetic resonance

Mn3O4 has Yafet-Kittel type spin structure below Neel Temperature (41K). The magnetization along the c-axis is smaller than that along the ab-plane even in external magnetic field of 30 Tesla, implying huge magnetic anisotropy in the ab-plane. We measured $^{55}$Mn$^{2+}$ and $^{55}$Mn$^{3+}$ Nuclear Magnetic Resonance (NMR) of a Mn$_{3}$O$_{4}$ single crystal in external magnetic field. The canting angles of Mn$^{2+}$ and Mn$^{3+}$ magnetic moments were calculated from the spectral shift obtained for various magnetic field directions between the a, b and c-axes. With the canting angle data, we estimated the anisotropy energies of the Mn$^{2+}$ and Mn$^{3+}$ magnetic moments and the exchange energy between them. The result also shows that Mn$^{3+}$ spins in the Yafet-Kittel structure lie in the ab-plane contrary to the previous reports.