La0.7Sr0.3MnO3 Research Articles

Tuning magnetoelectric effect in Bi6Fe1.6Co0.2Ni0.2Ti3O18/La0.7Sr0.3MnO3/Bi6Fe1.6Co0.2Ni0.2Ti3O18 sandwich films employing micromagnetic moments and force on dipole

Mutual modulating ferroelectric polarization and magnetization provides the potential for realizing new-type low-energy consumption, high-density memory, and logic processors. Despite extensive investigations, the underlying mechanism remains elusive. In this work, we employed Bi6Fe1.6Co0.2Ni0.2Ti3O18 (BFCNT) as the ferroelectric phase and La0.7Sr0.3MnO3 (LSMO) as the ferromagnetic phase to form environmentally friendly BFCNT/LSMO/BFCNT sandwich films fabricated on flexible FTO substrates using the all-solution chemical-solution deposition route. The ferromagnetism, ferroelectricity, and magnetoelectric coupling effect of the sandwich films were investigated by measuring at macro and micro scales. Then a dynamic micromagnetic moment model and a dipole force model were proposed to study the intermodulation of both ferromagnetism and ferroelectricity. It suggested that the combination of magnetic and electric moments makes the deflection of magnetization (or polarization) and a shift of the electron orbit, causing the movement of domain walls and the flip of magnetic domains, and thus a decrease of the saturation magnetization, offering new insights into the underlying physics of ME coupling in the model system.

Multifunctional Magnetic Oxide-MoS2 Heterostructures on Silicon.

Correlated oxides and related heterostructures are intriguing for developing future multifunctional devices by exploiting their exotic properties, but their integration with other materials, especially on Si-based platforms, is challenging. Here, van der Waals heterostructures of La0.7 Sr0.3 MnO3 (LSMO) , a correlated manganite perovskite, and MoS2 are demonstrated on Si substrates with multiple functions. To overcome the problems due to the incompatible growth process, technologies involving freestanding LSMO membranes and van der Waals force-mediated transfer are used to fabricate the LSMO-MoS2 heterostructures. The LSMO-MoS2 heterostructures exhibit a gate-tunable rectifying behavior, based on which metal-semiconductor field-effect transistors (MESFETs) with on-off ratios of over 104 can be achieved. The LSMO-MoS2 heterostructures can function as photodiodes displaying considerable open-circuit voltages and photocurrents. In addition, the colossal magnetoresistance of LSMO endows the LSMO-MoS2 heterostructures with an electrically tunable magnetoresponse at room temperature. This work not only proves the applicability of the LSMO-MoS2 heterostructure devices on Si-based platform but also demonstrates a paradigm to create multifunctional heterostructures from materials with disparate properties.

Spin Hall Induced Magnetization Dynamics in Multiferroic Tunnel Junction

AbstractThe combination of spin‐orbit coupling driven effects and multiferroic tunneling properties is explored experimentally in thin Pt/Co/BaTiO3(BTO)/La2/3Sr1/3MnO3(LSMO) multilayers. The presence of a Pt heavy metal allows for the spin current‐induced magnetization precession of Co upon radio‐frequency charge current injection. The utilization of a BTO ferroelectric tunnel barrier separating the Co and LSMO ferromagnetic electrodes gives rise to both tunneling‐ magnetoresistance and electroresistance. Using the spin‐orbit torque ferromagnetic resonance, the magnetization dynamics of the Co/Pt bilayers is studied at room temperature. Unexpectedly, the magnetization dynamics study in the same geometry performed at low temperature reveals the existence of both Co and LSMO resonance peaks indicating efficient spin current generation both using the spin Hall effect in Pt and spin pumping in LSMO that tunnel via the BTO barrier.

Investigating magnetic and magneto-transport properties of ferromagnetic (FM) structure and antiferromagnetic/ferromagnetic (AFM/FM) heterostructures

Electrical transport properties of functional magnetic oxides on the technologically important silicon substrate have been highly investigated in recent years for the spintronic applications. In this study, we probe the magnetic and magneto-transport properties of a hetero-structure of wide band gap semiconducting antiferromagnetic material (α-Fe2O3) and half metallic ferromagnet La0.7Sr0.3MnO3 (LSMO) and compare it with those of the LSMO single layer (thickness ∼60 nm) deposited on Si (100) substrate using pulsed laser deposition technique. X-ray diffraction θ-2θ scan validates the growth of α-Fe2O3 and LSMO phases, with no other impurity or secondary phase. Magnetic studies reveal that LSMO film shows Curie temperature close to 320 K and the bilayer shows the same at 255 K and another anomaly in the bilayer is at 102 K. LSMO single layer shows fairly high negative magnetoresistance (MR%) value of 41% at 214 K; close to MIT (metal-to-insulator temperature) at 230 K, and at 7 T field, which proves it to be potentially good candidate for spin transport across the heterostructure. α-Fe2O3 film shows no MR. Upon integration of α-Fe2O3 with LSMO, positive MR of about 10% is obtained, which stimulates to carry out further probe in spin excitations either optically or at higher magnetic fields across the heterostructures.

On the Role of the Sr3−xCaxAl2O6 Sacrificial Layer Composition in Epitaxial La0.7Sr0.3MnO3 Membranes

AbstractThe possibility to fabricate freestanding single crystal complex oxide films has raised enormous interest to be integrated in next‐generation electronic devices envisaging distinct and novel properties that can deliver unprecedented performance improvement compared to traditional semiconductors. The use of the water‐soluble Sr3Al2O6 (SAO) sacrificial layer to detach the complex oxide film from the growth substrate has significantly expanded the complex oxide perovskite membranes library. Nonetheless, the extreme water sensitivity of SAO hinders its manipulation in ambient conditions and restricts the deposition approaches to those using high vacuum. This study presents a pioneering study on the role of Ca‐substitution in solution processed SAO (Sr3−xCaxAl2O6 with x ⩽ 3) identifying a noticeable improvement on surface film crystallinity preserving a smooth surface morphology while favoring the manipulation in a less‐restricted ambient conditions. Then, the study focuses on the effect of the sacrificial composition on the subsequent ex situ deposition of La0.7Sr0.3MnO3 (LSMO) by pulsed laser deposition, to obtain epitaxial films with a variable degree of strain. Finally, epitaxial and strain‐free LSMO membranes with metal‐insulator transition at 290 K are delivered. This study offers a hybrid and versatile approach to prepare and easily manipulate crystalline perovskite oxide membranes by facilitating ex situ growth on SAO‐based sacrificial layer.

An investigation of Cr vaporization from SUS430 metallic interconnect and deposition on (La,Sr)MnO3 cathode of intermediate temperature solid oxide fuel cells

In solid oxide fuel cells (SOFCs), chromium deposition and poisoning of metallic interconnect is one of the most important issues in the electrochemical activity and stability of the cathode for the oxygen reduction reaction (ORR). In this paper, the chromium evaporation characteristics, oxide scale growth, and deposition of chromium on the ORR on (La,Sr)MnO3 (LSM) cathode are studied at 700–800 °C for SUS430 alloy interconnect material in the intermediate-temperature solid oxide fuel cells. The chromium vaporization rate is measured using the transpiration technique and the surface morphologies, and cross-sections of oxide scales are examined by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The results indicate that chromium volatilization is correlated with the composition and morphology of the oxide scale, the Cr volatilization process presents two stages according to the structural evolution of the oxide scale. In addition, deposition and poisoning of Cr species released from metallic interconnect on the LSM cathode are studied and the formation of MnCr2O4 phase on the LSM backbone degrades the ORR electrochemical activity, causing the increase of overpotential of the cathode. The results obtained give insight into the mechanism of the Cr poisoning effect in intermediate-temperature.

Electrochemical Impedance Spectroscopy of Core‐Shell Nanofiber Cathodes, with Ce0.9Gd0.1O1.95 (Core) and Cu‐Doped La0.6Sr0.4MnO3 (Shell), for Application in Solid Oxide Fuel Cells

AbstractSeveral core‐shell nanofiber electrodes are prepared through electrospinning and tested for application as intermediate‐temperature solid oxide fuel cell (IT‐SOFC) cathodes. The materials investigated are La0.6Sr0.4MnO3 (LSM), La0.6Sr0.4Cu0.1Mn0.9O3‐δ (LSCuM_1), and La0.6Sr0.4Cu0.2Mn0.8O3‐δ (LSCuM_2) perovskites, used at the shell side of the nanofibers. Ce0.9Gd0.1O1.95 (GDC10) fluorite is used as the core material. The electrochemical characterization of the core‐shell nanofiber electrodes is performed through electrochemical impedance spectroscopy (EIS). The EIS results are reported and discussed based on equivalent circuit modeling. The polarization resistance of the GDC10/LSM core‐shell nanofibers electrodes is RP∼4.5 Ω cm2 at 650 °C. Improvement is accomplished with GDC10/LSCuM_1 and GDC10/LSCuM_2 core‐shell nanofibers, with RP∼1.8 Ω cm2 and 1.7 Ω cm2 respectively at 650 °C. Post‐test SEM characterization is carried out, to ascertain possible degradation and identify the most promising shell perovskite.

Giant Spin-Valve Effect in Planar Spin Devices Using an Artificially Implemented Nanolength Mott-Insulator Region.

Developing technology to realize oxide-based nanoscale planar integrated circuits is in high demand for next-generation multifunctional electronics. Oxide circuits can have a variety of unique functions, including ferromagnetism, ferroelectricity, multiferroicity, superconductivity, and mechanical flexibility. In particular, for spin-transistor applications, the wide tunability of the physical properties due to the presence of multiple oxide phases is valuable for precise conductivity matching between the channel and ferromagnetic electrodes. This feature is essential for realistic spin-transistor operations. Here, a substantially large magnetoresistance (MR) ratio of up to ≈140% is demonstrated for planar-type (La,Sr)MnO3 (LSMO)-based spin-valve devices. This MR ratio is 10-100 times larger than the best values obtained for semiconductor-based planar devices, which have been studied over the past three decades. This structure is prepared by implementing an artificial nanolength Mott-insulator barrier region using the phase transition of metallic LSMO. The barrier height of the Mott-insulator region is only 55 meV, which enables the large MR ratio. Furthermore, a successful current modulation, which is a fundamental functionality for spin transistors, is shown. These results open up a new avenue for realizing oxide planar circuits with unique functionalities that conventional semiconductors cannot achieve.

Highly Tunable Perpendicular Magnetic Anisotropy and Anisotropic Magnetoresistance in Ru-Doped La0.67Sr0.33MnO3 Epitaxial Films

As a prototypical half-metallic ferromagnet, La0.67Sr0.33MnO3 (LSMO) has been extensively studied due to its versatile physical properties and great potential in spintronic applications. However, the weak perpendicular magnetic anisotropy (PMA) limits the controllability and detection of magnetism in LSMO, thus hindering the realization of oxide-based spintronic devices with low energy consumption and high integration level. Motivated by this challenge, we develop an experimental approach to enhance the PMA of LSMO epitaxial films. By cooperatively introducing 4d Ru doping and a moderate compressive strain, the maximum uniaxial magnetic anisotropy in Ru-doped LSMO can reach 3.0 × 105 J/m3 at 10 K. Furthermore, we find a significant anisotropic magnetoresistance effect in these Ru-doped LSMO films, which is dominated by the strong PMA. Our findings offer an effective pathway to harness and detect the orientations of magnetic moments in LSMO films, thus promoting the feasibility of oxide-based spintronic devices, such as spin valves and magnetic tunnel junctions.

Enhancement of La0.8Sr0.2MnO3-based amperometric total NOX sensor via modification with Pt nanoparticles

Pt nanoparticle (PtNP)-modified La0.8Sr0.2MnO3 (LSM)-sensing electrodes (SE) were developed successfully by the impregnation method for amperometric total NOX (NO and NO2) sensors. The structure, morphology, and surface valence state of SE were characterized by thermogravimetry (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The results showed that all SEs of the sensors were uniformly modified with PtNPs; interestingly, the size of the PtNPs increased with an increase in the modified content. Compared with pure LSM, the sensor based on 0.50 vol% Pt/LSM exhibited enhanced gas-sensing properties toward total NOX. The sensitivity improved from − 9.04 to − 18.7 μA/decade in the NOX, ranging from 50 ppm to 800 ppm. Moreover, the sensor maintained a 94% response signal after a long-term stability test, showing a stable response during the long-term thermal cycling test towards total NOX. Meanwhile, the sensor exhibited markable selectivity and consistency. The catalytic effect of Pt nanoparticles was believed to be the main reason for the enhancement of gas-sensing characteristics.

Performance and Electrochemical Behavior of LSM Based Fuel Electrode Materials Under High Temperature Electrolysis Conditions

Ni-YSZ is known as the state-of-the-art fuel electrode material for solid oxide cells. However, this conventional fuel electrode experiences severe degradation due to Ni- agglomeration and migration away from the electrolyte. Therefore, to avoid such issues, we have considered Ni free electrodes i.e. La0.6Sr0.4MnO3 (LSM) based perovskite oxides as fuel electrode. Under reducing atmosphere, the LSM perovskite phase transforms into a Ruddlesden-Popper (La0.6Sr0.4)2MnO4±δ phase. In addition to pure LSM fuel electrode, we have also investigated the performance of LSM+YSZ (50:50 wt %) and LSM+GDC (50:50 wt %) composite electrodes. The electrolyte-supported single cells were prepared using 8YSZ electrolyte supports, and in all cases, LSM+YSZ/LSM oxygen electrodes were used. The current-voltage characteristics show good performance for LSM and LSM+GDC fuel electrode containing single cells. However, a lower performance is observed for LSM+YSZ fuel electrode containing single cell. For instance, a current density of 997, 1025, and 511 mA.cm-2 at 1.5 V, are obtained for LSM, LSM+GDC, and LSM+YSZ fuel electrode containing single cells respectively, with 50% N2 and 50% H2O feed gas mixture.

Computational and Experimental Study on the Combined Sulfur and Chromium Poisoning Mechanism of LSM, LSCF and LNO Cathodes

Perovskites (La,Sr)MnO3 (LSM) and (La,Sr)(Co,Fe)O3 (LSCF) phases and Ruddlesden-Popper phase La2NiO4 (LNO) as solid oxide fuel cell (SOFC) cathodes, have been used due to its high efficiency and low emissions. To further understand the long-term degradation mechanism of the LSM, LSCF, and LNO phase in SO2 and Cr vapor gas impurities, they were prepared, sintered, and heat-treated at 800, 900, and 1000 ℃ in the sulfur, chromium, and water vapor-containing atmospheres, respectively. Later, XRD, SEM, and TEM techniques were applied to the samples, and corresponding simulations were made by the CALPHAD approach based on the same experimental conditions to verify the formation of the detrimental secondary phases. Results showed good agreement among the predictions and experiments. More importantly, extensive simulations were conducted under different conditions (temperature, the partial pressure of oxygen, and impurities) to understand the long-term degradation mechanism and optimize the operating conditions.

Local instability in GdBa2Cu3O7-x/La0.7Sr0.3MnO3 superconducting bilayer: Temperature-dependent EXAFS study

This study investigated the effect of local structural coupling between the buffer and the superconducting layers on the superconductivity of a GdBa2Cu3O7-x (GdBCO)/La0.7Sr0.3MnO3 (LSMO) bilayer. Epitaxial bilayers consisting of GdBCO with varying thicknesses (100, 300, and 500 nm), with and without LSMO (100 nm), were fabricated on a (001) SrTiO3 substrate. To investigate the local structural distortion within the GdBCO/LSMO system, the temperature-dependent extended X-ray absorption fine structure (EXAFS) spectra were measured at the Mn- and Cu–K absorption edges. The EXAFS analyses revealed local structural non-uniformity, which manifested as anomalies in the temperature dependence of both the Mn–O and Cu–O bond distributions. A strong correlation exists between the local structural distortion of the Mn–O bond and the degree of lattice instability in the CuO2 plane, which exhibits a strong thickness dependence. The inter-atomic potential of oxygen oscillations with an anharmonic approximation was adopted to interpret the structural anomalies. As a result, a double-well potential was obtained near Tc, owing to the occurrence of longer Cu–O bonds in the CuO2 plane. The difference in the degree of structural anomalies depending on the GdBCO thickness manifested as a difference in the distance between the two wells, which closely correlates with the appearance of a superconducting state. These experimental results demonstrate the role of local lattice fluctuations in the superconducting mechanism of the GdBCO/LSMO bilayer.

Reduced graphene oxide-wrapped La0·8Sr0·2MnO3 microspheres sensing electrode for highly sensitive nitrite detection

An electrochemical nitrite sensor based on perovskite oxides La0·8Sr0·2MnO3 (LSM) microspheres-decorated reduced graphene oxide (rGO) composite was presented to take the merit of the excellent electrocatalytic activity of the LSM and the large surface area of rGO. The content of rGO has been finely adjusted and the electrochemical sensor employing 15 wt% rGO has shown an ultralow nitrite detection limit of 0.016 μM and a high sensitivity of 0.041 μA μM−1 cm−2 and 0.039 μA μM−1 cm−2 in the range of 2–100 and 100–5000 μM, respectively. In addition, the proposed electrode shows good selectivity, reproducibility and stability, suitable for detection of nitrite at various pH values. The sensor was used to determine the nitrite level in environmental water samples with acceptable relative error, demonstrating its feasibility for practical environmental monitoring.

Interface Effects on Magnetic Flux Pinning in La0.7Sr0.3MnO3/YBa 2Cu3O7-x Bilayers.

The magnetic pinning properties of a ferromagnet/superconductor hybrid structure consisting of a La0.7Sr0.3MnO3(LSMO) layer with various thicknesses on top of a fixed thickness YBa2Cu3O7-x (YBCO) layer are investigated in this article. The existence of a weakly magnetic layer was identified at the interface between YBCO and LSMO by a ferromagnetic resonance (FMR) study. Magnetic moment and anisotropy of the interfacial layer were probed using the angular-dependent FMR study. This layer gives rise to an additional flux pinning contribution to the bulk magnetic pinning from the LSMO layer. Our study provides insight into the complex interface physics in the LSMO/YBCO bilayer system, promoting a new pathway for the development of novel flux pinning-related functionality.

Electrolyte Gated Synaptic Transistor based on an Ultra‐Thin Film of La0.7Sr0.3MnO3

AbstractDeveloping electronic devices capable of reproducing synaptic functionality is essential in the context of implementing fast, low‐energy consumption neuromorphic computing systems. Hybrid ionic/electronic three‐terminal synaptic transistors are promising as efficient artificial synapses since they can process information and learn simultaneously. In this work, an electrolyte‐gated synaptic transistor is reported based on an ultra‐thin epitaxial La0.7Sr0.3MnO3 (LSMO) film, a half‐metallic system close to a metal‐insulator transition. The dynamic control of oxygen composition of the manganite ultra‐thin film with voltage pulses applied through the gate terminal allows reversible modulation of its electronic properties in a non‐volatile manner. The conductance modulation can be finely tuned with the amplitude, duration, and number of gating pulses, providing different alternatives to gradually update the synaptic weights. The transistor implements essential synaptic features such as excitatory postsynaptic potential, paired‐pulse facilitation, long‐term potentiation/depression of synaptic weights, and spike‐time‐dependent plasticity. These results constitute an important step toward the development of neuromorphic computing devices leveraging the tunable electronic properties of correlated oxides, and pave the way toward enhancing future device functionalities by exploiting the magnetic (spin) degree of freedom of the half metallic transistor channel.

Light-Induced Decoupling of Electronic and Magnetic Properties in Manganites

The strongly correlated material La0.7Sr0.3MnO3 (LSMO) exhibits metal-to-insulator and magnetic transition near room temperature. Although the physical properties of LSMO can be manipulated by strain, chemical doping, temperature, or magnetic field, they often require large external stimuli. To include additional flexibility and tunability, we developed a hybrid optoelectronic heterostructure that uses photocarrier injection from cadmium sulfide (CdS) to an LSMO layer to change its electrical conductivity. LSMO exhibits no significant optical response, however, the CdS/LSMO heterostructures show an enhanced conductivity, with ~ 37 % resistance drop, at the transition temperature under light stimuli. This enhanced conductivity in response to light is comparable to the effect of a 9 T magnetic field in pure LSMO. Surprisingly, the optical and magnetic responses of CdS/LSMO heterostructures are decoupled and exhibit different effects when both stimuli are applied. This unexpected behavior shows that heterostructuring strongly correlated oxides may require a new understanding of the coupling of physical properties across the transitions and provide the means to implement new functionalities.

Temperature dependent transport characteristics of La0.9Sr0.1MnO3 / SrNb0.002Ti0.998O3 device

We report detailed investigations on device functioning capabilities of La0.9Sr0.1MnO3 (LSMO) manganite thin film fabricated on SrNb0.002Ti0.998O3 (SNTO) substrate. The LSMO / SNTO structure has been verified using XRD ϕ–scan measurement. We interpret the device capabilities by investigating the temperature dependent current–voltage (I–V) characteristics. To understand the linearity – nonlinearity nature and temperature effect, current ratio for specific voltages has been identified. Logarithmic scale variation in forward bias current with applied voltages has been studied at different temperatures. For the identification of backward diode behaviour possibility, I–V characteristics at typical temperatures have been studied for forward and reverse currents, simultaneously. The theoretical model fits supporting conduction mechanism in the device understudy has also been investigated for the typical I–V characteristics. The field effect configuration based variation in junction resistance of LSMO / SNTO structure with temperature under applied different junction electric fields and temperature dependent variation in electroresistance (ER) have been recorded to interpret the conduction processes undergoing in the device understudy.

Electric and magnetic tuning of Gilbert damping constant in LSMO/PMN-PT(011) heterostructure

Electric field control of magnetodynamics in magnetoelectric (ME) heterostructures has been the subject of recent interest due to its fundamental complexity and promising applications in room temperature (RT) devices. The present work focuses on the tuning of magnetodynamic parameters of epitaxially grown ferromagnetic (FM) La0.7Sr0.3MnO3 (LSMO) on a ferro(piezo)electric (FE) Pb(Mg0.33Nb0.67)O3-PbTiO3 (PMN-PT) single crystal substrate. The uniaxial magnetic anisotropy of LSMO on PMN-PT confirms the ME coupling at the FM/FE heterointerface. The magnitude of the Gilbert damping constant (α) of this uniaxial LSMO film measured along the hard magnetic axis is significantly small compared to the easy axis. Furthermore, a marked decrease in the α values of LSMO at positive and negative electrical remanence of PMN-PT is observed, which is interpreted in the framework of strain induced spin dependent electronic structure. The present results clearly encourage the prospects of electric field controlled magnetodynamics, thereby realising the RT spin-wave based device applications with ultra-low power consumption.

Electrical transport mechanism and magnetoresistive behavior of trilayer La0.7Sr0.3MnO3/γ-Fe2O3/La0.7Sr0.3MnO3 (FM/FIM/FM) manganites

The magnetization, electrical transport, and magnetoresistance (MR) behavior of Pulsed Laser Deposited polycrystalline tri-layer La0.7Sr0.3MnO3 (LSMO)/γ-Fe2O3/LSMO film and single layer LSMO film on Si (100) substrates are investigated in the temperature range of 5 K–300 K. A magnetic anomaly appears in the magnetization {M(T)} and resistivity {ρ(T)} characterizations of the trilayer film at around 100 K, which is quite robust and is present even at 7 T of the applied magnetic field. The trilayer sample exhibits metal to insulator (MIT) transition at 210 K. The transport behavior of both the films is analysed in the context of nearest-neighbour small polaron hopping model (SPH), Mott variable range hopping (VRH) mechanism as well as thermal activation (TA) model in different temperature ranges for both the films under study. The correlated polarons or less mobile bipolarons exist in the metallic regime of the trilayer sample due to the presence of magnetic inhomogeneities. The low temperature resistivity upturn is observed in LSMO film, which is attributed to the spin fluctuations (Mn3+–O–Mn4+) due to thermal energy. The trilayer sample exhibits a large negative MR of (∼45%) at low temperature (5 K). It manifests consistent negative CMR effect across the whole temperature range of 5 K–210 K (MIT). The improved MR behavior of the trilayer sample as compared to the LSMO film is due to enhanced polycrystalline character of the trilayer film owing to higher grain boundary density and spin dependent scattering at both the interfaces of LSMO/γ-Fe2O3/LSMO structure.