| Summary: | 碩士 === 國立雲林科技大學 === 材料科技研究所 === 105 === In this thesis, we focused on the magnetic properties of orthogonal magnetization MTJ structures. The multilayer films were prepared by ultra-high vacuum sputtering system. The structure is as following: substrate/antiferromagnetic layer/synthetic antiferromagnetic layer/spacer/free layer/cover layer. Spacer layer is MgO because of its higher tunneling resistance. The antiferromagnetic (AFM) and ferromagnetic (FM) layer interface causes exchange coupling to one of pin magnetic layer in the synthetic antiferromagnetic (SAF) layer. Co40Fe40B20 having a perpendicular magnetic anisotropy was prepared as a free layer in this structure.
By using the purer sputtering argon gas the thin film will show the smaller magnetic dead layer and larger coercive force. We speculated that the gas purity affect the film growth. When using IrMn as AFM layer, the ferromagnetic layer show good pinning effects even at as-deposited condition. While using the PtMn as AFM layer, the coercive force of the thin film approached zero at as-deposited condition. However, the thin films possess more coercive force and exchange bias after higher temperature annealing.
Furthermore, when the films were grown with lower sputtering rate, the surface are flatter and show better magnetic properties.
Field annealing (in parallel) produces an increased exchange bias, but lose the perpendicular magnetic anisotropy of free layer at the MTJ structure. In order to obtained perpendicular anisotropy again, we need to do the annealing without the external magnetic field.
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