Asghar Husain

Six-bit memory device capable of having multiple magnetization states is highly attractive as it can store six bits of information within a single cell. This corresponds to a 64-times enhancement in storage density relative to conventional one-bit technologies, offering substantial improvements in data capacity and computational efficiency. In this work, we successfully demonstrate 64 well-defined magnetization states (6-bit) in Ag/NiO/Ni/FTO devices by tuning the applied voltage, highlighting their potential for high-density multi-bit magnetic memory. The nature of these magnetization states is volatile. A substantial vertical magnetization shift in the hysteresis loop is observed when the magnetic field BZ and electric field EZ are parallel to each other. The calculated value of observed change in vertical magnetization shift is 165 emu·cc⁻¹ (76%) at 3.2 V with respect to 0 V. The pronounced shift is attributed to the pinning of interfacial spins, caused by resistive switching by oxygen-ion movement across the interface. The device exhibits analog resistive switching with stable, non-volatile behaviour over ~100 consecutive cycles. Reversible and reproducible magnetization switching is achieved by repeatedly applying the voltage in steps of 0.05 V, demonstrating the robustness of the voltage-controlled magnetic response. The vertical magnetization shift increases systematically with applied voltage. These capabilities highlight the potential of this system for improving the efficiency of spintronic devices and advancing multi-bit magnetic data storage.

Achieving strong perpendicular magnetic anisotropy (PMA) in Heusler alloys is highly beneficial for developing efficient and scalable spintronic devices. Here, we demonstrate the onset of PMA and its enhancement in Fe ₂ CoSi thin films through post-deposition annealing. X-ray diffraction confirms the A2 disordered phase. Williamson–Hall analysis reveals an increase in average crystallite size from ∼1.7–10.7 nm with annealing. Indeed, there is a reduction in lattice strain from 28.8 × 10 ⁻³ (room temperature (RT)) to 4.6 × 10 ⁻³ (film annealed at 550 °C), which indicates improved structural order. Enhanced structural order is confirmed with selective area electron diffraction. Magnetic measurements demonstrate an increase in coercivity (from ∼23 to ∼137 Oe) and saturation magnetization (from ∼1185 to ∼1407 emu cc ⁻¹ ) with annealing from RT to 550 °C, respectively. First-order reversal curve analysis shows a clear evolution from a compact single-domain state to a broadened multi-domain state. The enhanced full width at half maximum of switching-field distribution, minor-loop parameters ( W F 0 , W R 0 ), and appearance of stripe-like domains in magnetic force microscopy images further confirm the onset of PMA and its development. These findings infer that thermal annealing is an effective route to engineer anisotropy in Fe ₂ CoSi thin films for spintronic applications.

6-bit memory devices with different magnetization states are of great interest since they can encode six bits of information per memory cell. Indeed, this can cater a 64-fold increase in data storage capability compared to single-bit systems, which can significantly boost the data density and computational efficiency. Here, we demonstrate 64 distinct magnetization states (6-bit) by varying applied voltages, revealing the potential for 6-bit data storage capabilities in Ag/α-Fe₂O₃/Fe/FTO based devices. These magnetization states are volatile in nature. Large vertical magnetization shift of hysteresis loop in Ag/α-Fe₂O₃/Fe/FTO device is evident when electric field E _Z and applied magnetic field B _Z are parallel. Observed vertical magnetization shift is calculated to be 44 emu cc⁻¹ (79%) for the voltage bias of 3 V. This substantial change is attributed to interfacial spin pinning induced by resistive switching phenomenon through oxygen ion migration across the interface. The resistive switching shows analog characteristics with a non - volatile behavior for 95 cycles. Magnetization switching with high reversibility and reproducibility is shown by repeatedly applying 0.2 V and 1.2 V, underscoring the stability of the switching behaviour in the fabricated device. Magnetization shift changes with a change in voltage and it enhances as the applied voltage increases. This type of capabilities offer significant potential for advancing multi-bit data storage, which can enhance the efficiency of spintronic devices.