| Summary: | In order to realize a perpendicular exchange bias for applications, a robust and tunable exchange bias is required for spintronic applications. Here, we show the perpendicular exchange energy (PEE) in the Tb<sub>x</sub>Co<sub>100−x</sub>/Cu/[Co/Pt]<sub>2</sub> heterostructures. The structure consists of amorphous ferrimagnetic Tb–Co alloy films and ferromagnetic Co/Pt multilayers. The dependence of the PEE on the interlayer thickness of Cu and the composition of Tb–Co were analyzed. We demonstrate that the PEE can be controlled by changing the Cu interlayer thickness of 0.2 < t<sub>Cu</sub> < 0.3 (nm). We found that PEE reaches a maximum value (<i>σ</i><sub>Pw</sub> = 1 erg/cm<sup>2</sup>) at around x = 24%. We, therefore, realize the mechanism of PEE in the Tb<sub>x</sub>Co<sub>100−x</sub>/Cu/[Co/Pt]<sub>2</sub> heterostructures. We observe two competing mechanisms—one leading to an increase and the other to a decrease—which corresponds to the effect of Tb content on saturation magnetization and the coercivity of heterostructures. Sequentially, our findings show possibilities for both pinned layers in spintronics and memory device applications by producing large PEE and controlled PEE by Cu thickness, based on Tb<sub>x</sub>Co<sub>100−x</sub>/Cu/[Co/Pt]<sub>2</sub> heterostructures.
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