Heavy-Ion Irradiation Effects on Advanced Perpendicular Magnetic Anisotropy Spin–Orbit Torque Magnetic Random Access Memory Thin Films

摘要: This work examines the effects of heavy-ion irradiation on magnetic heterostructure thin film stacks, which constitute the core functional element of spin--orbit torque magnetic random access memory (SOT-MRAM). For advanced perpendicular magnetic anisotropy (PMA) SOT-MRAM thin films, 25 MeV/u Kr-ion irradiation experiments were performed with different fluences. Current-in-plane tunneling (CIPT) measurements indicate that, up to a fluence of 5 × 10¹¹ ions/cm², both the tunneling magnetoresistance (TMR) and the resistance--area product (RA) of the thin films exhibit negligible variation; when the ion fluence increases to 1 × 10¹² ions/cm², the TMR decreases by only ~ 5%, demonstrating robust electronic transport stability of the SOT-MRAM thin films under low-to-moderate fluence irradiation. The alternating gradient magnetometer (AGM) measurements indicate that, after irradiation, the saturation magnetization and the remanent magnetization of the thin films increase markedly, whereas the coercivity exhibits a decreasing trend with increasing fluence, indicating that irradiation alters magnetization reversal and pinning behavior. Microstructural characterizations indicate that irradiation-induced changes are predominantly concentrated in the MgO barrier layer and its interfaces: at high fluence, MgO lattice fringes become disordered, intermixing at the MgO/CoFeB interface is enhanced, and the Mg-related region broadens, with the full width at half maximum (FWHM) of the Mg distribution increasing from 1.48 ± 0.15 nm to 1.76 ± 0.19 nm. In contrast, the CoFeB ferromagnetic layer retains comparatively good structural and compositional stability. These findings provide material-level experimental evidence for understanding the irradiation response of PMA SOT-MRAM thin-film stacks, offering a useful reference for interface/barrier optimization of radiation-tolerant SOT-MRAM material stacks.