S. Narayana Jammalamadaka

We report on the resistive switching and synaptic properties of Ag/Cu _x O/FTO memristor device under combined optical and magnetic stimuli. The device demonstrated enhanced photocurrent under 633 nm laser illumination, attributed to photocarrier generation and oxygen vacancy formation. Concurrently, under an external magnetic field a reduced photocurrent was apparent due to magneto–optic modulation of conductance. Excitatory postsynaptic current (EPSC) measurements confirmed synaptic plasticity, revealing an increase in peak current with prolonged light pulses. Relaxation dynamics infer a trend toward long‐term plasticity from short‐term plasticity (STP) with magneto–optic stimuli. Enhancement in the refractive index and reduction in the optical absorption under magnetic field stimuli suggest a coupled magneto–optical and electrical response in the material. A single‐layer‐based artificial neural network (ANN) simulations were performed for pattern recognition. The obtained long‐term potentiation (LTP) and long‐term depression (LTD) conductance data from magneto–optic stimuli of Ag/Cu _x O/FTO device are used as synaptic weights to classify the MNIST dataset for pattern recognition. Software training gave a test accuracy of 92%, while it is 90% for the device conductance values‐based training for the MNIST handwritten dataset. These results would be helpful for the development of next‐generation magneto–optic‐based devices for neuromorphic computing.

Magnetic Weyl semimetals such as Co2MnGa are famous for exhibiting large anomalous Hall effect (AHE) due to intrinsic Berry curvature in their unique electronic band structure. However, because the AHE is also known to originate from extrinsic mechanism such as skew scattering and side-jump, it is important to clarify the role of extrinsic contribution to the AHE. In this study, we investigate the thickness dependence of the extrinsic contribution to the AHE in L21-ordered Co2MnGa single-crystal films from 8 to 90 nm epitaxially grown on MgO(001) substrates. A conventional scaling equation successfully reproduces the AHE of the 90 nm-thick film. The extrinsic contribution ratio reaches around 50%. In contrast, for the lower thicknesses especially below 24 nm, the AHE results are deviated significantly from the conventional scaling. We find that the AHE results are reproduced well using a modified scaling equation including additional extrinsic skew scattering. Our results indicate significant influence of extrinsic contribution on the AHE of the Weyl semimetal Co2MnGa films.

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.

This work investigates intrinsic coupling between magnetic, magnetostrictive, and magneto-transport responses in flexible Fe ₇₃ Ga ₂₇ /polyimide films. The magnetostriction exhibits a characteristic butterfly behaviour governed primarily by domain rotation processes with a maximum magnetostriction of ∼127 parts per million, indicating strong magnetoelastic coupling. Magnetic hysteresis measurements reveal dominant in-plane anisotropy, which strongly influences the field-dependent electrical transport. Magneto-resistance by four-probe measurements demonstrates well-defined resistance minima ( H _K1 , H _K2 ), which coincide closely with the magnetic coercive fields ( H _c ∼60 Oe (in-plane) & ∼560 Oe (out-of-plane)), demonstrating a direct magnetization-controlled transport mechanism. Temperature-dependent measurements (9–350 K) reveal a monotonic reduction in both magnetic coercivity ( H _c ) and characteristic transport fields ( H _K1 and H _K2 ), suggesting thermally assisted magnetic reversal associated with enhanced domain-wall depinning. The observed one-to-one correspondence between magnetic and electrical responses establishes robust magnetoelastic coupling in flexible Fe ₇₃ Ga ₂₇ /polyimide films, highlighting their suitability for strain-mediated sensing, magnetoelastic transduction, and flexible spintronic applications.

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.

Magnesium oxide (MgO) is important for the memory devices primarily in magnetic tunnel junctions (MTJs) for magnetic random‐access memory (MRAM) devices. Here we report on the multibit memory characteristics, conductance quantization and shape of the nanogap at the nano‐constriction in an Ag/MgO/FTO memristor device. Quantum point contact (QPC) analysis reveals a wide nanogap at the nano‐constriction, supported by an energy‐barrier aspect ratio of t _B / R ≈ 0.1947. The device exhibits stable bipolar switching with a window of ≈100, governed by space‐charge‐limited conduction in the high‐resistance state (HRS) and Ohmic transport in the low‐resistance state (LRS). During RESET, controlled filament rupture produces clear integer and half‐integer conductance quanta ( G ₀ ), enabling robust 4‐bit (18 levels) quantized states. Pulse‐programming measurements further demonstrate ≈6.5‐bit (96 levels) current states. These results elucidate atomic‐scale filament evolution in MgO and highlight its promise for precision multilevel memory. The cycle‐to‐cycle variation, non‐linearity, and asymmetry ratio for LTP and LTD demonstrate the potential of the Ag/MgO/FTO memristor device for neuromorphic computing applications.

An integrated magnetic flux concentrator (MFC) has become a choice for enhancing the sensitivity of a magnetic field sensor. However, the flux concentrator’s geometry and its ultra-soft magnetic properties are the key ingredients for successful implementation to improve the detectability of a magnetic sensor. In this report, the laminated stack of Ta/Ru/[NiFe(tNiFe)/Ta(tTa)]N/Ta of thickness 0.5 μm was investigated, where tNiFe, tTa, and N were varied to optimize ultra-soft magnetic properties of the film and compared them with the bulk NiFe film. Structural investigations revealed that incorporating an ultra-thin layer of Ta in the laminated stack suppresses the grain growth of the NiFe phase and improves the textured growth of the fcc(111) phase of the NiFe alloy. This results in dramatic improvement of the measured magnetic hysteresis loop of the laminated stack with a reduced coercivity field in the range of 0.4 ± 0.1 Oe, high linearity, and low saturation field (<10 Oe) while comparing them with the bulk film of NiFe of equivalent thicknesses. The laminated stack thickness of up to 4 μm was further investigated, and the bilinear M(H) loop was explained through antiferromagnetic (AFM) interlayer coupling between successive NiFe layers.

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.

Neuromorphic devices and their technologies have emerged as a novel approach to meet the growing demands of data‐intensive applications. It offers substantially higher energy efficiency compared to traditional computers which work based on von Neumann architecture. In this respect, tuning synaptic characteristics like long‐term potentiation (LTP) and long‐term depression (LTD) by external stimuli in a remote way can be an alternative energy efficient approach. Hence, the efforts in manifesting remote control of neuromorphic functionalities in α ‐Fe ₂ O ₃ ‐based synaptic device using magnetic field are reported. For this work, spintronic‐based material and fabricated Ag/ α ‐Fe ₂ O ₃ /fluorine‐doped tin oxide synaptic device are used. By the application of magnetic field strength ≈80 Oe, a significant change in LTP and LTD characteristics is evidenced. The change in conductance of the device with magnetic field is attributed to Lorentz force and spin‐dependent scattering. Herein, it is believed that modulation of LTP and LTD in a remote way will indeed pave a new approach in developing neuromorphic technologies. Apart from that Pavlov's classical conditioning, which is an associative learning mechanism in the biological brain, is also demonstrated.