The current-induced spin-orbit torques (SOTs) in the perpendicularly magnetized Ir22Mn78/Co20Fe60B20/MgO structures are investigated. The damping- and field-like torques are characterized using a harmonic technique. The spin Hall angle of Ir22Mn78 is determined to be θSHE = +0.057 ± 0.002. The SOT-driven magnetization switching is also demonstrated with the assistance of an external in-plane field. Furthermore, the magneto-optical Kerr effect imaging experiments show that the magnetization switching is realized through domain nucleation and domain wall motion. These results may promise potential practical applications in high-performance SOT devices based on the antiferromagnetic materials.

The large ferroelectric diode current modulated by bipolar polarization in epitaxial (111) BiFeO3 thin film has been observed. With the survey of different current leakage models, it is found that the space-charge limited current dominates the conduction. For the intrinsic physical understanding, the rectification of diode currents near domain coercive fields is attributed to gradient distribution of the trap charges between top and bottom electrode/ferroelectric interfaces, and the distributed charges can be reversed upon polarization reversal. Moreover, the retention time of the On and Off diode currents is over 104 s with their ratio of around 5:1.

Dynamic magnetic properties in perpendicularly exchange-coupled [Co/Ni]/Cu (t = 0-2 nm)/TbCo structures show strong dependences on the interfacial antiferromagnetic strength J, which is controlled by the Cu interlayer thickness. The precession frequency f and effective damping constant α of a [Co/Ni] multilayer differ distinctly for parallel (P) and antiparallel (AP) magnetization orientation states. For samples with a thin t, f of the AP state is apparently higher, whereas α is lower than that in the P state, owing to the unidirectional exchange bias effect (H) from the TbCo layer. The differences in f and α between the two states gradually decrease with increasing t. By using a uniform precession model including an additional H term, the field-dependent frequency curves can be well-fitted, and the fitted H value is in good agreement with the experimental data. Moreover, the saturation damping constant α displays a nearly linear correlation with J. It decreases significantly with J and eventually approaches a constant value of 0.027 at t = 2 nm where J vanishes. These results provide a better understanding and effective control of magnetization dynamics in exchange-coupled composite structures for spintronic applications.

The annealing effect and interlayer (IL) modulation on the magnetic damping properties of CoFeB/IL/Pt (IL = Ta or Ru) multilayers have been systematically studied by the time-resolved magneto-optical Kerr effect. It is found that after inserting a thin IL, the saturated magnetic damping factor αs drops considerably due to the reduced spin pumping effect. By fitting the curves of αs versus IL thickness, spin diffusion lengths of Ta and Ru are determined to be 3.07 and 3.59 nm, respectively. Interestingly, for the CoFeB samples with different capping layers of Pt, Ta/Pt, or Ru/Pt, the αs values exhibit an identical non-monotonic variation tendency as annealing temperature (Ta) increases. It first rises to a maximum at Ta ∼ 100 °C and then decreases, reaching a minimum value (αs = 0.021–0.011) at Ta ∼ 300 °C. After that, αs starts to increase again. Such a complicated variation behavior is attributed to two-magnon scattering contribution, which originates from the change in the CoFeB surface roughness and interfacial atomic intermixing induced by thermal annealing. This study provides a deep understanding and effective control of magnetic damping for practical design of high performance spintronic devices.

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