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The magneto-ionic modulation of the Dzyaloshinskii-Moriya interaction (DMI) and the perpendicular magnetic anisotropy (PMA), in W/CoFeB/HfO2 stacks annealed at different temperatures and for varying annealing times, are presented in this work. A large modulation of PMA and DMI is observed in the systems annealed at 390 and 350 °C, whereas no response to voltage is observed in the as-grown samples. A strong DMI is only observed in the samples annealed at 390 °C for 1 h, while PMA is present for all annealing times at temperatures of 390 and 350 °C. Magnetic properties including domain wall velocity improve drastically with increasing the annealing temperature and time, while the magneto-ionic reversibility is increasingly compromised. The changes in PMA and DMI induced by the gate voltages in the samples annealed at 390 °C are permanent, while partial reversibility is only observed for the samples annealed at 350 °C for short times. This dependence of reversibility on post-grown annealing has been associated to the influence of crystallization on ion mobility. These results show that a compromise between the enhancement of the magnetic properties and the magneto-ionic performance could be needed in systems requiring annealing to develop PMA and DMI. [ABSTRACT FROM AUTHOR]

Hard X‐ray nanodiffraction provides a unique nondestructive technique to quantify local strain and structural inhomogeneities at nanometer length scales. However, sample mosaicity and phase separation can result in a complex diffraction pattern that can make it challenging to quantify nanoscale structural distortions. In this work, a k‐means clustering algorithm was utilized to identify local maxima of intensity by partitioning diffraction data in a three‐dimensional feature space of detector coordinates and intensity. This technique has been applied to X‐ray nanodiffraction measurements of a patterned ferroelectric PbZr0.2Ti0.8O3 sample. The analysis reveals the presence of two phases in the sample with different lattice parameters. A highly heterogeneous distribution of lattice parameters with a variation of 0.02 Å was also observed within one ferroelectric domain. This approach provides a nanoscale survey of subtle structural distortions as well as phase separation in ferroelectric domains in a patterned sample. [ABSTRACT FROM AUTHOR]

Emerging nonvolatile memories (NVMs) have currently attracted great interest for their potential applications in advanced low-power information storage and processing technologies. Conventional NVMs, such as magnetic random access memory and resistive random access memory, suffer from limitations of low tunnel magnetoresistance, low access speed, or finite endurance. NVMs with synergetic advantages are still highly desired for future computer architectures. This study reports a heterogeneous memristive device composed of a magnetic tunnel junction (MTJ) nanopillar surrounded by resistive silicon switches, named resistively enhanced MTJ (Re-MTJ), which may be utilized for novel memristive memories, enabling new functionalities that are inaccessible for conventional NVMs. The Re-MTJ device features a high ON/OFF ratio of >1000% and multilevel resistance behavior by combining magnetic switching together with resistive switching mechanisms. The magnetic switching originates from the MTJ, while the resistive switching is induced by a point-switching filament process that is related to the mobile oxygen ions. Microscopic evidence of silicon aggregated as nanocrystals along the edges of the nanopillars verifies the synergetic mechanism of the heterogeneous memristive device. This device may provide new possibilities for advanced memristive memory and computing architectures, e.g., in-memory computing and neuromorphics. [ABSTRACT FROM AUTHOR]

Ferroelectric materials exhibit coupled degrees of freedom and possess a switchable electric polarization coupled to strain, making them good piezoelectrics and enabling numerous devices including nonvolatile memories, actuators, and sensors. Moreover, novel photovoltaic effects are encountered through the interplay of electric polarization with the material optical properties. Consequently, light‐induced deformation in ferroelectrics, or photostriction, combining photovoltaic and converse piezoelectric effects, is under investigation in the quest for multifunctional materials. Using time‐resolved X‐ray diffraction, the first control of ultrafast photoinduced strain is demonstrated through in situ tuning of the polarization state in ferroelectric‐based devices. Both the magnitude and the sign of the photoinduced strain strongly depend on the transient photoinduced change of the internal electric field in the ferroelectric layer, and can be actively engineered to achieve two distinct remanent photostrictive responses. These results provide fundamental insight into light–matter interaction in ferroelectrics and exciting new avenues for materials functionality engineering. [ABSTRACT FROM AUTHOR]