Deposition and Magnetic Properties of Fe3O4/Fe/Fe3O4Tri-layer Films

The Fe3O4/Fe/Fe3O4 (MIM) tri-layer films (200 nm/12 similar to 93 nm/200 nm) were prepared on Si(100) by DC-magnetron reactive-sputtering followed by air- or vacuum-annealing at 280 similar to 400 degrees C for 1.5 h, respectively. Magnetic properties and phases under different sandwich and annealing conditions were studied. In MIM structure, the incorporation of the interlayer iron does increase the magnetization measured under 8 kOe (M-8K), but reduce coercivity (H-c). The H-c of as-deposited films decreases from 354 Oe to 74 Oe, while M-8K increases from 254 to 392 emu/cc. By annealing in air, the whole MIM tri-layer film becomes gamma-Fe2O3 H-c is about 550 Oe and M-8K is around 250 emu/cc. The coercivity mechanism of as-deposited and annealed MIM trilayer films belongs to domain-wall pinning type. delta M plots show that when the interlayer Fe thickness is 12 nm, the Fe and Fe3O4 layers are decoupled in the as-deposited and annealed states, while it is coupled in the as deposited state when the Fe thickness increases to 23 nm. Vacuum annealing of the MIM films leads to increase in both coercivity and magnetization, and to enhance the exchange coupling between layers.