Tunnelling from Fe3O4

Recent experiments on magnetic tunnelling devices based on magnetite film s how an unexpectedly low tunnel magnetoresistance despite a high magnetic tr ansition temperature and a high spin polarization of the conduction electro ns. The, explanation is given in two parts. The first reason for the reduct ion is the quantum mechanical coupling and relaxation of the conduction ele ctron and core spin. This can reduce the tunnel magnetoresistance substanti ally. The second is the surface effects in which the magnetic spins at the surface are frustrated as a result of fewer nearest neighbours, surface rec onstructions, antiphase boundaries and the superparamagnetic behaviour. Thi s explains the rapid fall of the magnetization and the tunnel magnetoresist ance with temperature.