Spin-reorientation-triggered non-monotonic low-temperature coercivity and voltage-gated two-stage hydrogenation in PrCo5

The spin-reorientation transition (SRT) in rare-earth permanent magnets often reconfigures magnetic anisotropy, yet its direct impact on low-temperature coercivity remains underexplored. In this work, we report a non-monotonic temperature dependence of coercivity in PrCo5, governed by an SRT at 107 K that switches the easy magnetization direction from uniaxial to easy-cone. Such behavior is attributed to competing Pr 4f and Co 3d sublattice anisotropies, which are absent in non-SRT SmCo5. Voltage-controlled hydrogen ion insertion was then employed as a continuous, controllable, and mild tuning strategy to harness this behavior, enabling a two-stage modulation of both coercivity and SRT. These findings not only establish ion insertion as an effective approach for mapping and programming spin-reorientation-driven anisotropy landscapes but also highlight the promise of PrCo5 as a tunable functional material for designing adaptive magnetic memory devices under cryogenic conditions.