Mn⁵⁵ Nuclear Magnetic Resonance of the Mn³⁺ Ion Located at the B-Site in Manganese Ferrite Single Crystal—Anisotropic Hyperfine Field Due to the Local Jahn-Teller Distortion

Abstract

Nuclear Magnetic Resonance (NMR) of Mn⁵⁵ associated with the Mn³⁺ ion at the octahedral site in its magnetically ordered state has been studied on manganese ferrite of cubic phase. Using a single crystal sample, the large anisotropic hyperfine field of +115 kOe, in addition to the isotropic hyperfine field of −360 kOe, has been observed, which is characteristic of the Mn³⁺ ion at the octahedral site with the Jahn-Teller distortion. These two values of the hyperfine fields are consistent both with the theoretically calculated values and with the data of the hyperfine coupling constants of the paramagnetic Mn³⁺ ion. It was found that the ground state of the Mn³⁺ ion at the octahedral site was of B_1g type and that the directions of tetragonal axes (Jahn-Teller axes) were three equivalent ⟨100⟩ axes. In connection with the unsuccessful observation of the quadrupole-splitted lines, which are also characteristic of NMR in the MN³⁺ ion, the effects and the origins of the lower symmetry crystalline fields are discussed.