Effect of Mo insertion layers on the magnetoresistance and perpendicular magnetic anisotropy in Ta/CoFeB/MgO junctions

Abstract

The effect of a thin Mo dusting layer inserted at the interface of Ta/CoFeB of perpendicular magnetic tunneling junction with MgO barriers was investigated. Unlike thick Mo layers that exhibited a strong (110) crystalline texture, the inserted Mo layer between Ta/CoFeB had little negative influence on the crystallization of CoFe (001), therefore combining the advantages of Mo as a good thermal barrier and Ta as a good boron sink. For optimized Mo dusting thickness, a large tunneling magnetoresistance of 208% was achieved in perpendicular magnetic tunneling junctions with superior thermal stability at 500 °C.

Modulation of Heavy Metal/Ferromagnetic Metal Interface for High‐Performance Spintronic Devices

“…These features are mainly attributed to the B affinity of W and the strong PMA generated at the W/CoFeB interface. Similar results have been reported in several literatures . These findings benefit the compatibility of p‐MTJs with standard CMOS back‐end‐of‐line processes and make W and Mo more attractive than Ta for practical applications.…”

“…Consequently, by replacing the typical Ta layer with the Mo layer, a thermally robust perpendicularly magnetized CoFeB/MgO system could be realized. This result also suggested that there was little Mo diffusion during the high temperature annealing due to the large formation energy of Mo–Fe alloys . Besides, after annealing, interfaces in Mo (5 nm)/CoFeB (1.2 nm)/MgO (2 nm)/CoFeB (1.2 nm)/Mo (5 nm) stack are very neat, which is shown by the high‐resolution transmission electron microscopy (HR‐TEM) image in Figure a.…”

“…The crystallization of the MgO (001) texture is improved owing to the higher annealing temperature for the Mo‐inserted sample, further enhancing TMR due to the coherent tunneling preservation. Almasi et al reported that the TMR ratio could be dramatically improved by the insertion of Mo thin layer at the Ta/CoFeB interface . The Mo insert layer in the Ta/thin Mo/CoFeB/MgO/CoFeB/thin Mo/Ta stack serves as a thermal barrier to prevent the intermixing of Ta with Fe, while allowing smaller B atoms to diffuse out during the annealing process at 500 °C for 10 min.…”

Ion irradiation-induced easy-cone anisotropy in double-MgO free layers for perpendicular magnetic tunnel junctions

“…To increase the free(storage)-layer volume, V, and thus to improve the data retention, while keeping a strong PMA, two FeCoB/MgO interfaces may be used 1 . To absorb the boron out of the FeCoB layers upon the post-deposition anneals required to recrystallize the MgO barrier and the FeCoB ferromagnetic (FM) electrodes, a thin metal (e.g., Ta, W) spacer is usually introduced in the middle of the FeCoB storage layer [2][3][4][5][6][7] . Besides improving the data retention, the double-MgO storage layer also exhibits a reduced Gilbert damping, α, as compared to thinner ones sandwiched between a single MgO barrier and a heavymetal layer such as Ta or W. In the latter structures, a damping enhancement is often observed resulting from the spin-pumping effect.…”

Spin-Orbit-Torque Switching in 20-nm Perpendicular Magnetic Tunnel Junctions

“…with large TMR, careful control of the oxidation level results in the high Keff value that we observe here [33] [32]. If the bottom layer were considered as an isolated particle, its thermal stability factor = 47±2 and the anisotropy field is =>>, @ABBAC = 14.3 ± 1.3 kOe.…”