We have investigated optical and magnetic field tunability of capacitance across (100-x)% ZnO-x% rGO/La0.7Sr0.3MnO3 (x=0, 0.6, 0.8, 100) spintronic heterojunctions. ZnO-rGO/LSMO junction capacitance for device with 0.8% rGO is minimum due to larger space charge region (SCR) compared to other devices. Magnetic field dependent capacitance at heterojunction has been found to compensate capacitance at LSMO active region of the devices. High rGO content devices experience sharp fall of light dependent junction capacitance indicating higher dependency on light dependent SCR enhancement rather than accumulation of ZnO-rGO defect depinned carriers at junction parallel plates. Unlike 0 Oe, a sharp rise of light dependent capacitance from 0.12 to 0.26 nF (double) can be observed for thin SCR rGO device at high ambient magnetic field of 0.5 kOe. Reversal of light dependent junction capacitance trend for thin SCR devices has been attributed to field dependent enhancement of SCR.

This article analytically explores defect assisted spin injection in organic magnetic tunnel junctions (MTJs) [x/rubrene/Co, x = La2O3, LaMnO3, La0.7Ca0.3MnO3 (LCMO), La0.7Sr0.3MnO3 (LSMO)] employing nonequilibrium Green's function (NEGF). Spin precession at ferromagnet (FM)/organic semiconductor (OSC) interface defect states have been considered while modeling the MTJ devices. Variations in voltage dependent parallel (R-P) and antiparallel (R-AP) resistances have been attributed to modified spin dependent scattering at modified spin resolved density of states of magnetic electrodes. Moreover, change in distribution of defect state depths at a spin injection interface has also been observed to modify R-P/R-AP, and hence, tunnel magnetoresistance (TMR) across the devices. Localization of defect state distribution due to a high spin split band may have resulted in large TMR for La2O3 devices. Nonlinear spin transfer torque (STT) in devices other than LSMO indicates compensation of spin damping, resulting in a high TMR response across the devices. Hence, the localization of defect state distribution and the choice of magnetic electrodes with high spin split bands may be exercised to realize spintronic devices for low power spin memory applications. (c) 2024 Author(s).

Perovskite manganites are interesting materials in spintronic devices due to their significant magneto-transport properties. Here, magneto-transport study has been carried out on structurally characterized (100−x)

We have investigated glass content ratio dependent magneto-optical tunability of complex impedance spectroscopy study in La0.7Sr0.3MnO3 (LSMO)-Glass nanocomposites prepared through chemical pyrophoric reaction process. Interestingly, our experimental results provide evidence of optical tunability of magnetoimpedance ( MI %=Z(H,f)-Z(0,f)/Z(0,f)× 100 ) in these nanocomposites. Our experimental signature shows that MI increases with increasing weight percent of glass (x

Herein, analytical modeling of Fe 3 O 4 / x (≈1.1 nm)/Co ( x = rubrene, C 60 , and bathocuproine (BCP)) magnetic tunnel junctions (MTJs) has been performed using rubrene, C 60 , and BCP as organic spacer layers. The simulation is considered as nonequilibrium Green's function assuming spin precession at ferromagnet/organic semiconductor (FM/OSC) interface defect states. The voltage‐dependent resistances for both parallel ( R P ) and antiparallel ( R AP ) orientations have been observed to be dependent on spin injection from FM/OSC defect states. Pinning well‐dependent defect state depths have been associated with band misalignment‐induced lattice distortion at FM/OSC interface of the devices. The large tunnel magnetoresistance (TMR) response for rubrene‐based MTJ device has been attributed to a higher change of FM/OSC defect state depths with voltage. High TMR may have reduced spin torque‐dependent spin precession, leading to lower spin transfer torque for the rubrene device. Hence, engineering of defect states at the FM/OSC interface may lead to the successful realization of enhanced TMR in organic spacer MTJs for high‐performance spintronic memory applications.

We have studied the role of interface in charge transport across ZnO-rGO/La_0.7Sr_0.3MnO_3 (LSMO)/ITO heterostructure through impedance measurements and consequent fitting analysis of the experimental observations. The impedance data have been measured under varying magnetic field, and optical power of 660 nm red laser light. Our experimental signatures reveal contributions from both bulk and interface of the heterostructure. We have observed decrease in impedance with magnetic field up to 1.2 kOe. This decrease has been attributed to magnetic field assisted enhanced charge transport in the LSMO layer. However, at higher fields, depletion region in ZnO-rGO/LSMO interface widens, which in turn increases the charge carrier scattering thereby enhancing impedance of the heterostructure. In absence of any external magnetic field, light assisted dielectric relaxation in ZnO-rGO layer is found to be dominant up to 30.27 µW optical power. Under higher optical power, the light induced widening of ZnO-rGO/LSMO space charge region surges the charge carrier scattering, which in turn increases the impedance. In presence of constant 0.5 kOe field and varying optical power, combined effect of magnetic field and light has been observed in the impedance data. Interestingly, under simultaneous presence of 1.0 kOe field and varying optical power, a significant number of magnetic field induced defect states counterbalances the light induced increase in charge carrier scattering at moderate optical powers.

Light and magnetic field‐dependent carrier transport properties of ITO/(LSMO)/CuPc/Au (Device A) and p‐Si/(ZNFO)/CuPc/Au (Device B) heterostructure devices are investigated. Current (I)–voltage (V) response indicates efficient carrier tunneling through LSMO/CuPc and ZNFO/CuPc interface of the respective devices. Carrier injection (‐HOMO) with tunneling may be present at low bias for Device B, due to small band offset thereby leading to small nonlinearity in I–V curves. Light‐dependent measurements indicate efficient photocurrent generation aided by Frankel exciton generation at CuPc bulk and subsequent separation at LSMO/CuPc interface for Device A. Magnetic field‐dependent scattering both at LSMO/CuPc interface and LSMO bulk has been observed from impedance measurements. Positive magnetoresistance at low bias indicates high degree of positive spin polarization within ZNFO/CuPc interface, at room temperature. ZNFO/CuPc interface resistance reduces with field due to enhanced tunneling owing to reduction in depth of defect states. However, increase in ZNFO bulk resistance has been attributed to increase in interfacial polarization with magnetic field.

In this article, we have worked on defect-assisted spin transport at the ferromagnetic (FM)/organic semiconductor (OSC) interfaces leading to modified TMR response in hybrid magnetic tunnel junction (MTJ) devices. The simulation considers non-equilibrium Green’s function (NEGF) assuming spin precession at the FM/OSC interface defect states. Both the carrier injection (band-to-band) and phonon-assisted tunneling through the organic spacer optical gap led to modified spin transfer torque (STT) across the MTJ devices. Higher compensation of spin damping due to out-of-plane STT led to higher TMR response for the MTJ devices.

In this paper, we have investigated red light (∼660 nm) and magnetic field dependence of impedance across (100−x)% ZnO(zinc oxide)–x% rGO(reduced graphene oxide)/La0.7Sr0.3MnO3(LSMO)/ITO (x=0,0.6,0.8,100) heterostructure devices. Field-induced scattering due to the spin filter effect and spin polarized tunneling (SPT) have been extracted from the zinc oxide–reduced graphene oxide nanocomposite/LSMO space charge region (ZnO–rGO/LSMO SCR) and the LSMO active region of the devices, respectively. Higher SPT leads to higher LSMO SCR scattering across the devices. Devices with higher rGO contents could not be fitted with two RC circuits as resistance values because the two phenomena are incomparable with each other. Light-induced scattering has been observed at the ZnO–rGO nanocomposite active region and ZnO–rGO/LSMO SCR of the devices. For composite devices with x=0.8 and 0.6, higher photocarrier generation at ZnO–rGO nanocomposite active layer leads to enhanced scattering at LSMO SCR with light illumination. Light-dependent scattering at both regions, however, follows almost same decreasing trend for bare devices with x=0, 100. The decreasing trend of light-dependent scattering for ZnO/LSMO/ITO and rGO/LSMO/ITO bare devices suddenly gets reversed and, eventually, follows an increasing trend at magnetic field ambiance of 0.5 and 1 kOe, respectively. The LSMO SCRs of the bare devices got enhanced with the field, leading to a light-dependent response similar to composite devices at the higher field.

This electronic We have investigated supply noise reduction of Metal-Oxide-Semiconductor (MOS) based logic circuits both at 500 nm and 45 nm technology nodes. Logical failure of Complementary-MOS inverter with supply voltage lowering can be restricted at low package inductances. Noise reduction of 5-input combinational logic is performed by subsequently reducing number of transistors and applying dynamic logic within the design. The change of voltage level due to dynamic logic has been corrected using a proposed design where high capacitance paths from switching transistors to output reduces supply noise while maintaining logical reliability. Logic reconstruction occurs in level triggered D-flipflop with transistors reduction (18 to 10) at 45 nm technology node and package inductance as high as 1 mH. Supply noise for master-slave negedge triggered D-flipflop is found to be frequency dependent at low packages and large channel circuits. Large package and short channel contribute large noise current which makes the design almost independent of applied clock frequency.

We have investigated light and magnetic field dependent electrical transport response of (100−x)%ZnO-x%rGO/La0.7Sr0.3MnO3 (LSMO)/ITO (x = 0, 100, 0.6, 0.8) heterostructure devices at room temperature. Negative and positive magnetoresistance(MR) response, respectively for bare (x = 0, 100) and composite devices (x = 0.6, 0.8) is associated with spin dependent scattering at eg 2↑ and t2g↓ band of LSMO space charge region. Positive bias current, for bare devices, is supposed to have a defect induced suppression with light leading to an overall decrease of device current at low field. However, the bias current may have started increasing with light at high fields thereby reversing photosensitivity sign from negative (NPS) to positive (PPS). Such reversal from NPS to PPS has been attributed to high defect induced carrier transport through depinning of electrons from weak pinning centers with magnetic field. (100−x)%ZnO-x%rGO/LSMO barrier widths that are directly proportional with defect state population seem to support field induced change of photosensitivity behavior with light illumination.

We have investigated both red light (660 nm) and magnetic field (H) dependent carrier transport properties of ZnO-rGO/La0.7Sr0.3MnO3(LSMO)/ITO heterostructure at room temperature. H dependent current-voltage (I-V) response shows positive magnetoresistance behavior over the entire applied bias region. This phenomenon is attributed to larger spin dependent scattering of electrons at t↓2g band of LSMO depletion region with increase in H. Enhancement in device current with light intensity, at positive bias region and zero applied H, is supposed to be associated with dissociation of excitons at ZnO-rGO granular interface, ZnO-rGO/LSMO depletion region and LSMO active layer of the device. Device current is suddenly observed to decrease with light intensity at higher constant applied H of 1 kOe. Simultaneous light and magnetic field dependent modification of ZnO-rGO/LSMO depletion region is supposed to be the origin of such reversal of light dependent device current behavior at high magnetic field.

We have investigated photo-response as well as resistive switching behaviour in hybrid zinc oxide (ZnO)/reduced graphene oxide (rGO) bilayer thin film, equipped through sol–gel process on an ITO coated glass substrate under the dark and variation of light illumination. This ZnO/rGO photodetector reveals a stout photocurrent dependency on the colour of the lights illuminating (white and red laser light), where the magnitude of photocurrent has been found to increase exponentially with the increase in energy of photons of the incident light. In the same device, we have observed resistive switching behaviour and polarity effect of SET/RESET bias similar to that exhibited by the non-volatile memory device (NVRAM). The Ron (HRS resistance) and Roff (LRS resistance) ratio Ron/Roff is approximately 60 at bias voltage 2 V. We have explained this feature in light of filament formation and biasing effect on it. Photo annealing has been done to reduce GO to rGO for fabricating this device on ITO-coated glass substrate. Our study on electrical characterization of the ITO/ZnO/rGO/Au device explores the coexistence of photo-response and memresistive characteristics, which could be potential for developing multifunctional photodetector with memory effect.

We studied light and magnetic field dependent DC transport properties Zn0.3Ni0.7Fe2O4/ZnO-reduced graphene oxide composite heterojunction. Current through the heterojunction is expected from the carrier injection and tunneling in forward and reverse bias, respectively. Application of magnetic field has shown both negative magnetoresistance (MR) at forward bias and positive MR at reverse bias. The negative MR is attributed to the reduction of spin dependent scattering in the bulk of Zn0.3Ni0.7Fe2O4 layer. On the other hand, under reverse bias, a magnetic field dependent increase of depletion region in Zn0.3Ni0.7Fe2O4 side is supposed to take place, resulting in a positive MR. Under 660 nm visible light illumination, photoresponse has been observed. Under illumination, negative MR is found in reverse bias. This negative MR is expected to be associated with the magnetic field dependent widening of reverse bias depletion region. In forward bias voltages, under strong illumination of 3.08 mW/cm(2) of 660 nm light, a positive MR is found. This positive MR is associated with the light dependent enhancement of depletion width at Zn0.3Ni0.7Fe2O4 side under high injection mode. When the applied voltage is swept along a cycle, irreversible nature of I-V characteristics is observed.

We have demonstrated modeling of phonon and defect-induced spin relaxation length (L-S) in Fe3O4 and organic semiconductor (OSC) Alq(3). L-S of Alq(3) decreases with enhanced disorder and film thickness at a low film width regime. Exponential change of L-S at low width regime is found for Alq(3) which is, however, absent for Fe3O4 indicating comparable spin-dependent scattering and L-S in Fe3O4. L-S also decreases with spin-flip probability both for Alq(3) and Fe3O4. Voltage-dependent tunnel magnetoresistance (TMR) response in Fe3O4/Alq(3)/Co and La0.7Sr0.3 MnO3 (LSMO)/Alq(3)/Co hybrid magnetic tunnel junction (MTJ) devices has been attributed to modified spin filter effect across magnetic/OSC junction at high bias regime. TMR reduction with Alq(3) thickness for Fe3O4 device has been attributed to spin relaxation at the organic spacer layer. A low bias peak from differential TMR indicates spin-polarized injection for both MTJ devices. Enhanced in-plane spin transfer torque for both MTJ is associated with modified spin filtering at magnetic/OSC junctions. Lower TMR signal for LSMO device indicates reduced tunneling and enhanced carrier injection across the OSC, which is also supported by the band structure profile. The TMR response observed from simulation results matches well with previously reported experimental results. Higher TMR response for Fe3O4 device indicates the possibility of device employment in room temperature magnetic recording applications.

We have presented experimental results addressing the origin of spin valve (SV) magneto-resistance (MR), in both injection and tunnel conduction regimes, in our fabricated Fe3O4 (111)/Alq3/Co SV device. Experimental evidences have shown that any alternative MR process, such as 'tunneling anisotropic MR' is not at the origin of this SV MR. Spin resolved density of states of electrodes indicate that both the conduction mechanisms induce different spin dependent scattering which inturn modify the MR signal of the device. This modification helped in maintaining a non-monotonous quenching of MR signal with increase in temperature. We have also proposed a phenomenological model for device operation where the concept of charge gap modification at Fermi level across Verwey transition is envisaged to offer this unique scenario of tuning the conduction mode and hence MR in this ferrite based organic SV. The model is also supported by an established theoretical study which considers high temperature phonon assisted tunneling through defect states at electrode–organic interface of the device.

In this article, we provide an initial qualitative description of the basic magnetization reversal processes behind temperature and cooling field-dependent exchange bias effect at Co/CoO interface of Fe 3 O 4 /Alq 3 /Co/CoO/Au hybrid spin valve (SV) device structure. The exchange field at Co/CoO interface is observed to be inversely proportional to temperature, indicating enhanced magnetic field sensitivity of Co reverse domain nucleation at the high-temperature region. The exchange field, at constant temperature, is found to be insensitive to change in the cooling field, which may be due to efficient ferromagnetic coupling at the Co/CoO interface of the device. Sudden decrease of exchange field with training cycle number (n) has been observed at lower values of n, which may be attributed to rearrangement of Co pinned layer spin configuration toward equilibrium. Interestingly, incorporation of antiferromagnetic CoO layer has not been observed to bring any change in magnetoresistance (MR) behavior of the exchange biased SV device, which shows a two-step switching pattern of MR at 100 K.

In this paper, we have carried out numerical analysis (modeling and simulation) on current (I)-voltage (V) characteristics of both pristine P3HT and P3HT: PCBM blend both under equilibrium and non-equilibrium conditions. Non-equilibrium condition in the materials is assumed to be associated with mutually exclusive deviation of photosensitive device parameters from equilibrium values due to light illumination. Current in both pristine P3HT and P3HT: PCBM blend are observed to increase with increase in electron mobility, hole mobility and carrier density within the material. Photosensitivity for both the materials is larger at negative voltage since enhanced exciton generation and dissociation takes place at P3HT grain boundaries and P3HT/PCBM interface of pristine P3HT and P3HT/PCBM blend, respectively. Finally, DC photoresponse for our simulated OPD device structure ITO/P3HT/P3HT:PCBM/Au (Device A) is observed to be faster than the OPD structure of ITO/ P3HT:PCBM/Au (Device B) indicating enhanced carrier injection and transport aided by the extra hole transport layer of P3HT in Device A.

Interface effect on magnetotransport properties have been explored through proper tuning of Polyvinyl Alcohol concentration of 0.5%(S1), 1%(S2) and 1.5%(S3) in La0.7Sr0.3MnO3(LSMO)-Polyvinyl Alcohol nanocomposites, prepared through solid state reaction route. Polyvinyl Alcohol chemisorbed grain boundaries (GB) of LSMO lead to distortion of Nyquist semicircles indicating non Debye type electrical relaxation process in the system. Decrease in GB resistance (RGB) with magnetic field (H), indicates depinning of GB domain walls from GB pinning centres. Very small intergranular distance in clustered LSMO grains, seem to attribute minimum low frequency impedance in S3, amongst all the samples. Magnetoresistance (MR) studies indicate significant variation of MR with Polyvinyl Alcohol concentration at low temperature regime where efficient SPT in S3 due to cluster formation is strongly reflected. Dependence of surface spin magnetization on Polyvinyl Alcohol chemisorbed interface has been observed to be more dominating at low temperature region.

A reasonable modification of an established phenomenological model is developed to investigate the recent report on sign reversal of magnetoresistance (MR) in 99.95% La0.7Sr0.3MnO3(LSMO)−0.05% paraffin wax hybrid nanocomposite system. At zero external magnetic field (H), all the grain boundary (GB) domain walls (DWs) are assumed to remain pinned at the pinning well. Due to depinning of spin‐polarized DWs with H, a negative MR response is observed between 15 K and 300 K. The GB DWs, which are expected to be pinned with strong pinning strength at and below 10 K, have undergone spin‐flip tunneling, thereby increasing the resistance of the composite with H, i.e., positive MR. The strong pinning phenomenon associated with positive MR is analytically modeled using a skewed Gaussian distribution of pinning strength at and below 10 K.