• Journal of the Korean Magnetics Society
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• v.21 no.1
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• pp.10-14
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• 2011

We have measured the ferromagnetic resonance (FMR) signal in as deposited and $400^{\circ}C$ annealed CoFeB/MgO thin film to investigate the annealing effect on magnetic anisotropies and FMR linewidth (${\Delta}H_{PP}$). The uniaxial anisotropy field ($H_{K1}$) was only observed in the as deposited sample. Whereas, in the $400^{\circ}C$ annealed sample, the biaxial anisotropy field ($H_{K2}$) was additionally observed in accompany with uniaxial anisotropy field ($H_{K1}$). The appearance of biaxial anisotropy fields was originated from the crystalline growth of bcc CoFeB(001) from the MgO(001) interface and by the B diffusion during thermal annealing. Also, the ${\Delta}H_{PP}$ of $400^{\circ}C$ annealed sample was increased compared with that of as deposited sample, which was due to the broad distribution of the magnetization axis by the biaxial anisotropy.

• Proceedings of the Korean Magnestics Society Conference
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• 2011.06a
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• pp.25-26
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• 2011

• Journal of the Korean Magnetics Society
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• v.21 no.3
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• pp.83-87
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• 2011

We have analyzed the torque signals measured in synthetic antiferromagnetic (SAF) coupled CoFeB/Ru/CoFeB thin film, which signals were drastically changed at flopping field ($H_F$) and saturation field ($H_s$). The minimum value of negative uniaxial anisotropy constant ($-\;K_1$) was appeared at HF. The $-\;K_1$ was due to the zero net magnetization by the antiferromagnetic coupling between two ferromagnetic layers. Whereas, the biaxial anisotropy constant (K2) was induced in the field range of $H_F$ < H < $H_s$. The induced $K_2$ was originated from deviation angles between magnetization directions of two ferromagnetic layers. And at H > $H_s$, intrinsic uniaxial anisotropy constant of CoFeB layer was observed. These change of the anisotropy constant with magnetic field was explained by the magnetization process of two ferromagnetic layers based on Stoner-Wohlfarth model calculation for SAF thin film.