A tetrahedral magnetic cluster surrounded by metallic atoms is studied in the framework of the Hubbard model. The ground-state energy and the wave function are obtained exactly using the Lanczos numerical diagonalization method. The spin/spin correlation functions /spl gamma//sub ij/=<S/spl I.oarr//sub i//spl middot/S/spl I.oarr//sub j/> and the total spin… (More)