MnO3 Thin Films Research Articles

Enhanced optoelectronic and supercapacitive performance of electrodeposited Mn3O4 thin film prepared from two-electrode: An effect of Zn-ion incorporation

Here in, we report electrodeposited Mn3O4 thin film doped with various level of Zn dopant (0≤x≤5.0,%), on a layer of indium tin oxide (ITO) on glass substrate. The deposition route involves the use of two-electrode electrochemical cell system comprising graphite and the substrate as counter and working electrodes, respectively. Some surface properties such as those of morphological, crystal structure, optical, electrical and electrochemical were studied to evaluate the films’ potentials in energy conversion and storage devices. Microstructural studies revealed the films grew with isotropic morphology of good tetragonal shaped crystal structure with even distribution and possessing required surface area on the substrate surfaces. Raman prominent peak at 659 cm −1 wave number indicates a typical A1g Raman vibrating mode of Mn2+ in a Mn3O4 spinel structure. The crystallite size and microstrain values were found varying from 38 to 43 nm and 5.6 × 10−3 to 3.2 × 10−3, with respect to increase in dopant content, respectively. Energy band gap and Urbach energy were varied from 3.28 to 2.68 eV and 1.59 to 2.17 eV with increasing level of dopant content, accordingly. Electrochemical charge storage area capacitance (12.62 to 21.35 mF cm −2)/capacity (5.1 to 8.1μAh cm −2) and rate capability of Mn3O4 electrode were found to improve with Zn dopant. The work therefore discusses the tailoring of band absorption and supercapacitive characteristic of electrodeposited Mn3O4 thin film with Zn-doping for enhanced energy application.

Interfacial quantum interference effect and dual magnetoresistance in La0.7Sr0.3MnO3 thin films grown on (001) Si

Transmission electron microscope image and electronic transport of La0.7Sr0.3MnO3 (LSMO) films grown on (001) oriented Si using the sputtered pulsed plasma method confirmed the presence of around 8 nm thick, less dense, and highly resistive LSMO at the interface below the conducting phase. Thicker LSMO films, in addition to metal-insulator transition, show an anomaly around the Curie temperature in temperature-dependent resistivity and magnetoresistance (MR), which is a unique observation. The conduction in these LSMO films at temperatures below low-temperature resistivity minimum is dominated by Kondo-like scattering over electron–electron scattering, established using the phenomenological model. At 20 K, the maximum positive MR is ∼ 12% for the in-plane field, while it is ∼ 7.2% for the out-of-plane field. The maximum negative in-plane MR is found to be ∼ 42.5%, which becomes ∼ 30% when the orientation of the field changes to the out-of-plane direction. The two-dimensional field-dependent change in the magneto-conductance model evidenced the quantum interference effect (QIE). The existence of QIE is associated with magnetic scattering and scattering due to spin–orbit coupling. These results may be used to modulate the electrical properties of future electronic devices and can encourage scientists to explore the multi-functionalities of complex oxides grown on bare Si substrates.

The Modulated Magnetic Domain Structure in the La0.67Sr0.33MnO3 Ferromagnetic Films by Strain Engineering

Novel magnetic domain structures attract much attention due to their potential applications in the high performance of spintronic devices. Herein, the magnetic domains of La0.67Sr0.33MnO3 (LSMO) thin films, which epitaxially grown on (100)-, (110)-, and (111)-oriented (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) substrates, are systematically investigated. The (100)- and (110)-LSMO films show a stripe domain pattern. After in-plane magnetic field saturation, the direction of the stripe domains in (100)-LSMO no longer rotates with the change of magnetic field, while the stripe domains in (110)-LSMO rotate continuously. The (111)-LSMO films produce randomly distributed bubble-like magnetic domains, which gradually connect into strips with the increase of the external magnetic field, and the stability of the magnetic domain in (111)-LSMO is better than the ones in (100)- and (110)-LSMO under a magnetic field. In addition, it is found that with the increase of thickness, the random domains in (111)-LSMO films are gradually transformed into mazy domains. These phenomena can be understood by the regulable strain anisotropy and the magnetic anisotropy. Herein, an effective way is suggested to modify the magnetization anisotropy and magnetic domain because spin polarization depends strongly on the crystal surface orientation as well as epitaxial strain.

Bipolar resistive switching with multiple intermediate resistance states in Mn3O4 thin film

Bipolar resistive switching with multiple intermediate resistance states in Mn3O4 thin film

Morphology control of volatile resistive switching in La0.67Sr0.33MnO3 thin films on LaAlO3 (001)

The development of in-memory computing hardware components based on different types of resistive materials is an active research area. These materials usually exhibit analog memory states originating from a wide range of physical mechanisms and offer rich prospects for their integration in artificial neural networks. The resistive states are classified as either non-volatile or volatile, and switching occurs when the material properties are triggered by an external stimulus such as temperature, current, voltage, or electric field. The non-volatile resistance state change is typically achieved by the switching layer’s local redox reaction that involves both electronic and ionic movement. In contrast, a volatile change in the resistance state arises due to the transition of the switching layer from an insulator to a metal. Here, we demonstrate volatile resistive switching in twinned LaAlO3 onto which strained thin films of La0.67Sr0.33MnO3 (LSMO) are deposited. An electric current induces phase transition that triggers resistive switching, close to the competing phase transition temperature in LSMO, enabled by the strong correlation between the electronic and magnetic ground states, intrinsic to such materials. This phase transition, characterized by an abrupt resistance change, is typical of a metallic to insulating behavior, due to Joule heating, and manifested as a sharp increase in the voltage with accompanying hysteresis. Our results show that such Joule heating-induced hysteretic resistive switching exhibits different profiles that depend on the substrate texture along the current path, providing an interesting direction toward new multifunctional in-memory computing devices.

Ferroelectric-polarization modulation of charge-to-spin conversion in Pb(Mg1/3Nb2/3)O3–Pb0.7Ti0.3O3/La0.67Sr0.33MnO3 system

Modulation of charge-to-spin conversion through active control is supposed to manipulate efficiency in a wide range for future spintronic devices. Despite its great significance, passive control still dominates the manipulation while the active control of charge-to-spin conversion is still challenging. Here we experimentally observe spin pumping-type charge-to-spin conversion besides Rashba-type one in La0.67Sr0.33MnO3 thin films deposited on ferroelectric Pb(Mg1/3Nb2/3)O3–Pb0.7Ti0.3O3 (PMN-PT) substrate. We exhibit that both two types of charge-to-spin conversion efficiency give rise to a variety of sign under positive and negative remnant polarized states of PMN-PT, which can be ascribed to the effect of ferroelectric polarization. The possibility of modulating charge-spin conversion opens a route for designing low-energy spintronics.

Coexistence of volatile and nonvolatile memristive effects in phase-separated La0.5Ca0.5MnO3-based devices

In this work, we have investigated the coexistence of volatile and nonvolatile memristive effects in epitaxial phase-separated La0.5Ca0.5MnO3 thin films. At low temperatures (50 K), we observed volatile resistive changes arising from self-heating effects in the vicinity of a metal-to-insulator transition. At higher temperatures (140 and 200 K), we measured a combination of volatile and nonvolatile effects arising from the synergy between self-heating effects and ferromagnetic-metallic phase growth induced by an external electrical field. The results reported here add phase separated manganites to the list of materials that can electrically mimic, on the same device, the behavior of both neurons and synapses, a feature that might be useful for the development of neuromorphic computing hardware.

A Cryostat Applicable to Long-Wavelength Light-Driven Scanning Probe Microscopy

Recently, there has been growing interest in using lightwave-driven scanning probe microscopy (LD-SPM) to break through the Abbe diffraction limit of focusing, yielding insight into various energy couplings and conversion processes and revealing the internal information of matter. We describe a compact and efficient optical cryostat designed for LD-SPM testing under magnetic fields. The exceptional multilayer radiation shielding insert (MRSI) forms an excellent temperature gradient when filled with heat conducting gas, which removes the requirement to install an optical window in the liquid helium cooling shell. This not only critically avoids the vibration and thermal drift caused by solid heat conduction but also minimizes light transmission loss. The application of gate valves and bellows allows a simpler and more effective replacement of the sample and working cell in the test cavity. ANSYS software is used for steady-state thermal analysis of the MRSI to obtain the temperature distribution and heat transfer rate, and the necessity of the flexible copper shielding strips is illustrated by the simulations. The topography and magnetic domain images of 45 nm-thick La0.67Ca0.33MnO3 thin films on NdGaO3(001) substrates under a magnetic field were obtained by a self-made lightwave-driven magnetic force microscope in this cryostat. The resolution and noise spectra during imaging reveal temperature stability and low vibration throughout the cryostat. The experience acquired during the development of this cryostat will help to establish cryostats of similar types for a variety of optic applications requiring the use of cryogenic temperatures.

Intrinsically strained hexagonal Sr0.6Ba0.4MnO3 oxygen partial pressure dependent texturing and weak ferromagnetic behavior

We have probed the effect of intrinsic strain on the structural and magnetic properties of magneto-electric hexagonal Sr0.6Ba0.4MnO3 (SBMO) thin film grown by pulsed laser deposition on LaAlO3 (110) substrate by varying oxygen partial pressure (OPP). While the grown films show hexagonal structure with varying OPP, transition from oriented to polycrystalline growth is observed with increase in OPP. Raman spectroscopy confirms the P63/mmc symmetry of grown films along with the indication of distortion of octahedral. Magnetization measurements reveal room temperature weak ferromagnetic behavior in the thin films, which is in contrast to antiferromagnetic nature of its bulk counterpart. X-ray magnetic circular dichroism measurement confirms weak ferromagnetic behavior with contribution from unquenched orbital magnetic moment.

Hierarchically Engineered Manganite Thin Films with a Wide-Temperature-Range Colossal Magnetoresistance Response.

Colossal magnetoresistance is of great fundamental and technological significance in condensed-matter physics, magnetic memory, and sensing technologies. However, its relatively narrow working temperature window is still a severe obstacle for potential applications due to the nature of the material-inherent phase transition. Here, we realized hierarchical La0.7Sr0.3MnO3 thin films with well-defined (001) and (221) crystallographic orientations by combining substrate modification with conventional thin-film deposition. Microscopic investigations into its magnetic transition through electron holography reveal that the hierarchical microstructure significantly broadens the temperature range of the ferromagnetic-paramagnetic transition, which further widens the response temperature range of the macroscopic colossal magnetoresistance under the scheme of the double-exchange mechanism. Therefore, this work puts forward a method to alter the magnetic transition and thus to extend the magnetoresistance working window by nanoengineering, which might be a promising approach also for other phase-transition-related effects in functional oxides.

Conductive path and local oxygen-vacancy dynamics: Case study of crosshatched oxides

By employing scanning probe microscopy, conductive path and local oxygen-vacancy dynamics have been investigated in crosshatched La0.7Sr0.3MnO3 thin films grown onto flat and vicinal LaAlO3(001) single crystal substrates. Consistent with prior studies, the crosshatch topography was observed first by dynamical force microscopy as the epi-stain started to release with increasing film thickness. Second, by using conductive atomic force microscopy (CAFM), conductive crosshatch and dots (locally aligned or random) were unravelled, however, not all of which necessarily coincided with that shown in the in situ atomic force microscopy. Furthermore, the current–voltage responses were probed by CAFM, revealing the occurrence of threshold and/or memristive switchings. Our results demonstrate that the resistive switching relies on the evolution of the local profile and concentration of oxygen vacancies, which, in the crosshatched films, are modulated by both the misfit and threading dislocations.

Interaction of water and carbon monoxide with MnO(001) thin films on Au(111).

Atomically defined MnO(001) thin films were grown on an Au(111) substrate, and their interaction with water (D2O) was investigated by infrared reflection absorption spectroscopy (IRAS) and thermal desorption spectroscopy (TDS). Carbon monoxide adsorption experiments were performed to probe surface atoms and defects on oxide films. Next, water interaction was investigated from which an associative binding pathway and a dissociative binding pathway were revealed, where the water molecules adsorb at terraces and water dissociation takes place at oxygen vacancies mediated by nearby Mn2+ sites. The IRAS data are supported by TDS experiments, which also manifest the importance of defects in the adsorption characteristics of MnO.

Growth and electronic properties of Co-doped Mn3O4 thin films: a combined experimental and theoretical investigation.

In this study, we have prepared and investigated the electronic properties of a new and promising cobalt doped Mn3O4 oxide surface by site-selective and element-sensitive X-ray-absorption (XAS) and photoemission spectroscopy (XPS and resonant PES) combined with density functional theory (DFT) calculations. The crystallinity of both pristine and Co doped thin films was ensured by low energy electron diffraction measurements, in which similar diffraction patterns were obtained for both films suggesting the inclusion of the dopant species within the crystalline Mn3O4 thin film. According to our combined experimental data and theoretical calculation results, XAS measurements and replace energy calculations could identify Co impurities adopting preferentially a 2+ oxidation state substituting a Mn2+ cation on tetrahedral sites (80%) as well as the Mn3+ on octahedral sites (20%). Direct evidence of these findings could be found by comparing the pristine Mn3O4 electron absorption and photoemission spectral features with those of the doped ones. For instance, the formation of oxygen vacancies related to the formation of Co2+ in an octahedral site could be directly observed. Remarkably, the valence band spectrum of Co-Mn3O4 thin films presents additional spectral features close to the Fermi edge that can be directly attributed to Co states when compared to the PDOS obtained by the DFT calculations. It is noteworthy that the formation and stabilization of these Co dopant species in the host Mn3O4 surface could potentially affect and obviously modulate its capability for adsorption of molecular species and transfer of electrons, which makes the cobalt doped Mn3O4 surface potentially promising for catalytic applications.

The Magnetic Properties and Magnetocaloric Effect of Pr0.7Sr0.3MnO3 Thin Film Grown on SrTiO3 Substrate

The magnetic behaviors and magnetocaloric effect (MCE) of Pr0.7Sr0.3MnO3 (PSMO-7) film grown on a (001) SrTiO3 single-crystal substrate by a pulsed laser deposition (PLD) were studied in this paper. X-ray diffraction with a high resolution (HRXRD) measurement shows that PSMO-7 film is grown with a (001) single orientation. The magnetic properties and the MCE related to the ferromagnetic (FM) phase transition of the PSMO-7 film are investigated using the temperature dependence of magnetization M(T) and the magnetic field dependence of magnetization M(H). The M(T) data suggest that with decreasing temperatures, the PSMO-7 film goes through the transition from the paramagnetic (PM) state to the FM state at around the Curie temperature (TC). The TC (about 193 K) can be obtained by the linear fit of the Curie law. Magnetic hysteresis loop measurements show that the PSMO-7 film exhibits the FM feature at temperatures of 10, 100, and 150 K (low magnetic hysteresis can be found), while the film reveals the PM feature with the temperature increased up to 200 and/or 300 K. The research results of M(H) data are consistent with the M(T) data. Furthermore, the magnetic entropy change (-ΔSM) of the PSMO-7 film was studied. It was found that the maximum value of (-ΔSM) near TC reaches about 4.7 J/kg·K under the applied field change of 20 kOe, which is comparable to that of metal Gd (-ΔSM of 2.8 J/kg K under 10 kOe), indicating the potential applications of PSMO-7 film in the field of magnetic refrigeration.

Bending Switch of Gigahertz La0.67Sr0.33MnO3 Thin Film Under Spin Wave Excitation

Spin waves, used for information processing and transmission, promise huge potential in the applications of the spintronic devices with low loss, minimal sizes, and high frequency. More attentions have been focused on all-magnon data processing utilizing traveling spin waves and moving domain walls. Bending control of spin wave is an effective modulation method for magnetic properties, and easily attuned to the trends of flexible magnon spintronics in future. In this work, we demonstrate the excitation of spin waves in the flexible La0.67Sr0.33MnO3 thin film by mechanical bending, which can be taken as the states for On and Off in microwave single-pole single-throw switches. Besides, the microwave magnetisms of the unbent and bending La0.67Sr0.33MnO3 thin films have been studied. The bending of La0.67Sr0.33MnO3 thin films does not change the microwave ferromagnetic resonance field. Our results demonstrate that the controllable spin wave state by mechanical bending has enormous potential for future flexible magnon spintronics.

Oxygen vacancy-induced enhancement in magnetism and magneto-transport properties in Sm0.55Sr0.45MnO3 thin films

Oxygen vacancy-induced enhancement in magnetism and magneto-transport properties in Sm0.55Sr0.45MnO3 thin films

Chemical solution deposition of epitaxial La0.7Sr0.3MnO3 thin films by laser-assisted annealing

Chemical solution deposition of epitaxial La0.7Sr0.3MnO3 thin films by laser-assisted annealing

Anomalous low-energy carrier dynamics of stripe-type charge ordered Pr0.5Sr0.5MnO3 thin film revealed by magneto-terahertz spectroscopy

The perovskite manganites host a range of charge- and orbital-ordered phases wherein the intrinsic and extrinsic controls of magnetic field, doping, epitaxial strain, chemical pressure, etc., induce subtleties of phase transition. The Pr0.5Sr0.5MnO3 (PSMO) is one such system that possesses a unique stripe-type charge-order manifesting in anisotropic transport. It exhibits a Drude-type and charge-density-wave (CDW) type of low-energy phases; the magnetic field is contemplated as a key control for both these phases; however, it has not yet been explored. Here, we have investigated the magnetic-field dependence of Drude-type terahertz (THz) carriers dynamics and the CDW type of low-energy excitations along two non-identical orthogonal in-plane axes of the (110) epitaxial thin film in the energy range of 1–7 meV using magneto-THz time-domain spectroscopy in Faraday geometry. While THz Drude conductivity expectedly increases with the increasing magnetic field, the CDW type of resonance absorption peak anomalously strengthens with the field. The origin of this unusual field-induced stabilization of the CDW-type mode is expected to lie in the d(x2–y2) orbital ordering in the A-type antiferromagnetic ordered state and anisotropic charge ordering. This study brings out a unique facet of the effect of magnetic field on orbital ordering of anisotropic stripe-type charge-ordered PSMO, which has potential THz modulation and switching applications.

Current modulations of the metal-insulator phase transition in epitaxial thin films of Pr0.7Sr0.3MnO3

Pr[Formula: see text]Sr[Formula: see text]MnO3 thin films were grown epitaxially on SrTiO3 and LaAlO3 substrates by pulse laser deposition. X-ray diffraction spectra obtained on these films revealed good crystallinity and epitaxy. It was found that the oxygen deficiency and in-plane strain may affect the transport behavior and phase transition near Curie temperature in these Pr[Formula: see text]Sr[Formula: see text]MnO3 films. Also, the resistance and metal-insulator phase transition could be modulated significantly by the applied electric currents. The reduction ratio of the peak resistance reached −38% for a bias current [Formula: see text]A, demonstrating a remarkable electroresistance effect. The results are interpreted based on the spatial inhomogeneity related to the coexisted multi-phases with different electronic and magnetic properties.

Multi-field modulation of transport properties in critical state (La1-yPry)0.5Sr0.5MnO3 thin films

Multi-field modulation of transport properties in critical state (La1-yPry)0.5Sr0.5MnO3 thin films