Dynamical Nature of Superexchange Interaction in Y3Fe5O12 Studied by Neutron Spectroscopy

Abstract

AbstractInelastic neutron scattering is used to investigate spin interactions in polycrystalline Y3Fe5O12. Neutron spectra due to local spin interaction are observed and interpreted by the 6S5/2‐term splitting of Fe3+ ions located in octahedral (a)‐sites and tetrahedral (d)‐sites of the garnet structure. The observed neutron spectra are analyzed using a phenomenological spin Hamiltonian assuming combined interaction of magnetic and quadrupole electric moments of the 3d5 electron shell with a static magnetic molecular field and a static electric field gradient, respectively. The neutron energy peaks connected with various magnetic coordination numbers at (a)‐sites and (d)‐sites are obtained. This phenomenon is interpreted as due to the dynamical nature of superexchange interaction of Fe3+ ions in YIG. The dynamical interactions bring about fluctuations of the magnetic moments with a relaxation rate between 10−8 s > τm > 10−13 s. The quadrupole and superexchange interaction parameters are determined to D = −0.508 meV and Es = 3.00 meV, respectively. The effect of lowering of magnetic moments of Fe3+ ions situated on (a)‐ and (d)‐sites is discussed.