Annealing effect on interlayer exchange coupling in perpendicularly magnetized synthetic antiferromagnetic structure based on Co/Pd multilayers with ultrathin Ru spacer

The magnetic properties of Co/Pt and Co/Pd multilayers of perpendicular synthetic antiferromagnets with an Ir spacer were investigated. A strong interlayer exchange coupling of $$J_{\mathrm{{ex}}}=2.01$$ J ex = 2.01 $$\mathrm{{erg/cm}}^2$$ erg / cm 2 was observed in the Co/Pt-based structures and a lower value of $$J_{\mathrm{{ex}}}=1.04$$ J ex = 1.04 $$\mathrm{{erg/cm}}^2$$ erg / cm 2 was found in the Co/Pd multilayers. Only the former revealed a high post-annealing stability at $$T_a=330\,^{\circ }$$ T a = 330 ∘ C, as the latter exhibited a ferromagnetic coupling most likely due to the deterioration of the spacer by pinhole coupling. This assumption was confirmed by theoretical calculations of the total energy functional. Moreover, the high temperature stability of Ir-based Co/Pt p-SAF structures was verified by calculating the exchange field $$H_{\mathrm{{ex}}}$$ H ex from magnetization M(H) loops as a function of temperature, where it reached a temperature of $$T_b=370\,^{\circ }$$ T b = 370 ∘ C before losing all interlayer exchange coupling.

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Temperature stability of Co/Pt and Co/Pd synthetic antiferromagnets using an Ir spacer

Caseiro

Macedo

Araujo

et al. 2023

J Mater Sci: Mater Electron

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Interlayer exchange coupling and interface magnetic anisotropy with crossed in-plane and perpendicular magnetic anisotropies

et al. 2020

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We investigated interlayer exchange coupling (IEC) and interface magnetic anisotropy (Ki) between two ferromagnetic layers with crossed in-plane and perpendicular magnetic anisotropies separated by a non-magnetic spacer by using the anomalous Hall effect (AHE). The sample consisted of a Co0.75Fe2.25O4 layer with perpendicular magnetic anisotropy and a Fe layer with in-plane anisotropy, separated by a MgO layer with variable thickness. Since Co0.75Fe2.25O4 and MgO are insulators, the AHE signal only reflects the magnetization process of Fe. From this, we determined both IEC and Ki. A strong antiferromagnetic IEC was confirmed between Co0.75Fe2.25O4 and Fe. The strongest IEC of −1.1 mJ/m2 was observed for directly coupled Fe and Co0.75Fe2.25O4 for which Ki was −1.1 mJ/m2.

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TaFeB spacer for soft magnetic composite free layer in CoFeB/MgO/CoFeB-based magnetic tunnel junction

Nakano

Fujiwara²,

Kumagai³

et al. 2023

Applied Physics Letters

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CoFeB/MgO/CoFeB-based magnetic tunnel junctions (MTJs) with a soft magnetic composite free layer have been developed for magnetic sensor applications. Tunnel magnetoresistance (TMR) ratios in the sensor-type MTJs have reached a ceiling due to a trade-off between the TMR ratio and interlayer exchange coupling (IEC) depending on the spacer thickness of the composite free layer. In this study, we developed a paramagnetic amorphous TaFeB-alloy spacer to replace the conventional Ta spacer and solve this trade-off. The TaFeB film showed a wider thickness window for a sufficient IEC, resulting in IEC energy values of 0.18–0.19 erg/cm2 at a thickness of 1.0 nm. In addition, we confirmed that the TaFeB film had an ability to function as a boron sink comparable to that of pure Ta. These characteristics allowed us to thicken the TaFeB spacer up to 1.0 nm in the sensor-type MTJs and attain an enhanced TMR ratio of up to 234%, which is the highest compared with cases using the conventional Ta spacer reported to date. These findings demonstrate that TaFeB alloy is a promising material for breaking the ceiling of sensor-type MTJs and increasing sensitivity.

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Annealing effect on interlayer exchange coupling in perpendicularly magnetized synthetic antiferromagnetic structure based on Co/Pd multilayers with ultrathin Ru spacer

Cited by 6 publications

References 21 publications

Temperature stability of Co/Pt and Co/Pd synthetic antiferromagnets using an Ir spacer

Temperature stability of Co/Pt and Co/Pd synthetic antiferromagnets using an Ir spacer

Interlayer exchange coupling and interface magnetic anisotropy with crossed in-plane and perpendicular magnetic anisotropies

TaFeB spacer for soft magnetic composite free layer in CoFeB/MgO/CoFeB-based magnetic tunnel junction

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