First-Principles Study Of Spin Properties And Laser-Induced Ultrafast Spin Dynamics In Transition-Metal Oxide Clusters Tm3o30/+ (Tm = Fe, Co, And Ni)

We present a first-principles study of spin properties of the triplet TM3O30/+ (TM = Fe, Co, Ni) clusters and their laser-induced ultrafast spin dynamics. The differences in geometries, infrared spectra, and level distributions of the three structures are discussed. It is found that the spin localization of the clusters is both structurally and magnetic-field dependent. Specifically, within the same magnetic field, the number of the spin-localized states decreases when the magnetic center changes from Fe via Co to Ni. Even for the same cluster, the spin-localized states may differ under different field directions, due to the fact that spin magnitudes and spin directions of the states change with magnetic field. For the spin dynamics, the results indicate that the system which possesses more spin-localized states normally exhibits rich spin functionalities. Among the various achieved laser-induced ultrafast spin-transfer scenarios, a spin-transfer cycle in Fe3O3, a partial demagnetization process in Co3O3+, and a spin bifurcation scenario in Ni3O3 are presented and analyzed, respectively. These results provide added information for the varieties of ultrafast optical control of magnetism in transition-metal oxide systems, and pave the way toward future related device design and molecular spintronics applications.