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The 3-D physical models for FeNi/Cu/FeNi films with two different types of structures that are linear and meander are developed. The relationship between the impedance of the films and the applied magnetic field or excitation frequency is obtained, and the influence of geometric parameters and structures of the films on the giant magnetoimpedance (GMI) effect is analyzed. The result shows that the GMI effect in the film with a horizontal meander structure appears to be much stronger compared with that in a linear structure. The negative mutual inductance of the meander FeNi/Cu/FeNi films reduces the total inductance and decreases the frequency response. Meanwhile, the GMI effect and the negative mutual inductance are enhanced by increasing the number of turns or decreasing the space width between each segment. Based on these effects, the FeNi/Cu/FeNi film with a vertical meander structure is proposed and simulated, which reflects the design of the meander structure in the thickness direction. The distance between each segment is reduced to 500 nm. The GMI effect and the negative mutual inductance are greatly enhanced (the maximum value of the GMI ratio increases from 207% to 1247% when the excitation frequency changes from 50 to 300 MHz). Furthermore, the spatial resolution of the film is further improved. The results obtained could be useful both for a better understanding of the GMI effect of the FeNi/Cu/FeNi film with a meander structure and for providing a choice for the device preparation of highly sensitive magnetic sensors. [ABSTRACT FROM AUTHOR]

The current-induced perpendicular magnetization switching in $L1$ 0-FePt single layer and Ta/FePt bilayer thin films was investigated. Here, $L1$ 0-FePt (6 nm) single-layer film and Ta (1–5 nm)/FePt (6 nm) bilayer films were deposited on MgO substrate at 700 °C, showing good perpendicular anisotropy with out-of-plane coercivity of 7.5 kOe for FePt and around 5 kOe for Ta/FePt bilayers. It was found that the current-induced partial magnetization-based switching was realized with the spin–orbit torque (SOT) switching ratio of about 3% in all films. For adding the Ta capping layer, the critical current density is reduced and the stability of the switching loop is relatively better when compared to the single FePt layer. Furthermore, harmonic Hall voltage results demonstrate that the SOT efficiency ($\beta _{\mathrm {DL}}$) of FePt single layer is approximately 50 Oe/(107 A cm−2) and significantly higher than that of Ta/FePt bilayers, which is several times higher than that of the traditional Ta/CoFeB/MgO structure reported earlier. More importantly, Ta/FePt bilayer structure exhibits very good memristive switching behavior, which is expected to be applied to the spin-synapse of neural networks in the future. [ABSTRACT FROM AUTHOR]

The performance of TiN/HfO2/Ag resistive random-access memory (RRAM) devices combining the oxygen-based RRAM (OxRRAM) and conducting bridge random-access memory (CBRAM) was studied. Current compliance (CC) values could significantly affect the resistive switching process: with unidirectional CC, permanent breakdown for the devices was observed. With bidirectional smaller CC, the stable bipolar resistive switching mode was obtained, and the cation injection played a leading role in the resistive switching process, while the devices with higher CC always remained in low-resistance state (LRS). The resistance–voltage (R–V) curve and conducting mechanism were analyzed for the bidirectional smaller CC devices, indicating ohmic conduction for the LRS, while the space charge limited the current for the high-resistance state. The results of x-ray photoelectron spectroscopy showed that oxygen vacancies participated in the resistive switching process. It could be concluded that conducting paths were formed from conducting filaments of oxygen vacancies and conducting bridges of Ag grains, and the different formation rate of conducting filaments related to the values of CC was the prime reason for the various changes. Moreover, the characteristics of TiN/HfO2/Ta devices proved the universality of bidirectional CC. The method of making the OxRRAM and CBRAM coexist in the RRAM devices may offer a way to fabricate devices with low power consumption. [ABSTRACT FROM AUTHOR]