Microstructure and magnetic properties of FePt-MgO granular thin films fabricated by Co-sputtering method on the single crystal MgO substrate

摘要

L1-FePt film has the high magnetocystalline anisotropy energy (K), large coercivity (H) and it is an ideal high density magnetic recording material. However, L1-FePt ordered phase is obtained by high temperature annealing, which is prone to increase the grain size of FePt. The large size grains cause the surface roughness increase, which is the source of the noise during the recording process. MgO is chosen for its widely application in the tunnel junction devices and it has a suitable lattice mismatch with FePt (4%) [1]. The FePt granular thin film with co-deposited MgO non-magnetic matrix is beneficial to suppress the FePt grain growth during annealing and decrease the exchange coupling effects between the FePt grains [2]. The utilization of MgO single crystal substrate induces the deposition of MgO matrix because of the homogeneous structure, which has the advantages of the formation of the inter-granular phase between FePt grains. In this paper, the FePt-MgO films were prepared by co-sputtering on the single crystal <;100> MgO substrate in magnetron sputtering system. The microstructure and magnetic properties are investigated. The targets are FePt and ceramic MgO. The deposition temperature was varied from room temperature to 300. The As-deposited FePt-MgO films were annealed at 800 for 1hour. The composition of FePt and MgO was configured by the power of the targets (both RF and DC power). All the films were characterized by XRD, AFM/MFM, and VSM.