Single-layer La0 Research Articles

Prototype Design of a Domain-Wall-Based Magnetic Memory Using a Single Layer La0.67Sr0.33MnO3 Thin Film.

Magnetic field-free, nonvolatile magnetic memory with low power consumption is highly desired in information technology. In this work, we report a current-controllable alignment of magnetic domain walls in a single layer La0.67Sr0.33MnO3 thin film with the threshold current density of 2 × 105 A/cm2 at room temperature. The vector relationship between current directions and domain-wall orientations indicates the dominant role of spin-orbit torque without an assistance of external magnetic field. Meanwhile, significant planar Hall resistances can be readout in a nonvolatile way before and after the domain-wall reorientation. A domain-wall-based magnetic random-access memory (DW-MRAM) prototype device has been proposed.

Magnetic domain formation in ultrathin complex oxide ferromagnetic/antiferromagnetic bilayers

In this study, we report on the magnetic domain formation in ultrathin blanket films and patterned micro- and nanostructures of ferromagnetic (FM) La0.7Sr0.3MnO3 single-layers and antiferromagnetic (AF)/ferromagnetic LaFeO3/La0.7Sr0.3MnO3 bilayers, as investigated by soft x-ray photoemission electron microscopy. In single-layer La0.7Sr0.3MnO3, the domain size is significantly reduced compared to that found in thicker layers, and rectangular micromagnets display metastable multidomain states distinctly different from the flux-closure ground states commonly found in thicker elements. In the LaFeO3/La0.7Sr0.3MnO3 bilayers, complex multidomain patterns are observed for blanket films and patterned magnets with robust perpendicular (spin-flop) coupling between spins in the AF and FM layers. By thermal cycling of the sample through the La0.7Sr0.3MnO3 Curie temperature, we find that the native antiferromagnetic domain pattern of LaFeO3 pins the location of domain boundaries in the adjacent La0.7Sr0.3MnO3 layer.

Effects of lanthanum strontium cobalt ferrite (LSCF) cathode properties on hollow fibre micro-tubular SOFC performances

Single layer La0.6Sr0.4Co0.2Fe0.8O3 hollow fibre (HF) precursors (<1 mm ID) produced by phase inversion (PI) were sintered at 1,200, 1,350 and 1,400 °C. The increase in sintering temperature resulted in microstructural changes in the LSCF fibres, reflected in their electrical conductivities. LSCF-based cathodes with different designs were brushed onto co-extruded nickel–gadolinium-doped ceria (CGO) anode/CGO electrolyte dual-layer HFs (<1 mm ID) fabricated by PI. The effect of cathode layers on the overall performance of the fuel cells (FCs) was assessed using nearly identical anode and electrolyte compositions, thicknesses, and microstructures. Cathode microstructure design caused cells to perform differently producing peak power densities of 0.35–0.7 W cm−2 at 600 °C. Impedance spectroscopy analysis at 600 °C on the FCs produced 0.12–0.24 Ω cm2 confirming the cathode’s structural effect on the overall area-specific resistance of the FCs. The best performing FC with a brush-deposited cathode was compared to a similar FC where cathode was deposited by dip coating; at 600 °C the first produced 0.6 W cm−2 while the second cell 0.7 W cm−2. Co-extruding anodes and electrolytes by using PI and combining dip coating for cathode deposition could lead to the fabrication of FCs with enhanced microstructures and improved performances.

Magnetocaloric effect in epitaxial La0.56Sr0.44MnO3 alloy and digital heterostructures

This work investigates the magnetocaloric effect of two epitaxial manganite heterostructures, one being a single layer La0.56Sr0.44MnO3 alloy with randomly distributed La and Sr cations, the other a digitally synthesized superlattice of LaMnO3 and SrMnO3 fabricated to be compositionally identical to the alloy. The magnetic entropy change and relative cooling power were larger for the alloy than the superlattice, though both are suppressed relative to bulk materials. These results indicate that disorder of the A-site cation species in the perovskite structure may play a crucial role in defining the magnetocaloric effect in complex oxide materials.

Improved oxidation resistance of ferritic steels with LSM coating for high temperature electrochemical applications

The effect of single layer La0.85Sr0.15MnO3−δ (LSM) coatings on high temperature oxidation behaviour of four commercial chromia-forming steels, Crofer 22 APU, Crofer 22 H, E-Brite and AL 29-4C, is studied. The samples were oxidized for 140–1000 h at 1123 K in flowing simulated ambient air (air + 1% H2O) and oxygen and corrosion kinetics monitored by mass increase of the materials over time. The oxide scale microstructure and chemical composition are investigated by scanning electron microscopy/energy-dispersive spectroscopy. The kinetic data obey a parabolic rate law. The results show that the LSM coating acts as an oxygen transport barrier that can significantly reduce the corrosion rate.

Room Temperature Magnetoresistance at Low Magnetic Fields in La 0.7 Ba 0.3 MnO 3

This paper examines the possibility of enhancing the room temperature magnetoresistance at low applied magnetic fields in single layer La0.7 Ba0.3 MnO3 thin films. The influence of lattice mismatch strain, as well as the effect of different frequency regimes, on the magnetoresistance is explored. The effects of lattice mismatch strain are studied by measuring the magnetoresistance as a function of the La0.7 Ba0.3 MnO3 film thickness, oxygen annealing, and lattice matched buffer layers. We find that the release of the lattice mismatch strain improves the magnetoresistance at room temperature and at low magnetic fields. In fact, the highest magnetoresistance at room temperature (−1.7% at 500 Oe) has been found for the 1600 A as-grown La0.7 Ba0.3 MnO3 film, whereas the largest magnetoresistance (−1.9% at 500 Oe) is found at 309 K for the 1000 A La0.7 Ba0.3 MnO3 film annealed in flowing O2 for 1 h at 900°C. Finally, we find that the microwave magnetoresistance is the same as the dc magnetoresistance when the cavity corrections are applied. In the single layer La0.7 Ba0.3 MnO3 system, the low field magnetoresistance at room temperature is far from being technologically viable.

Desirable magnetotransport properties in doped Mn-oxide-based superlattices

Superlattice structures based on doped Mn-oxides and SrTiO3 exhibit desirable magnetotransport properties, such as an enhanced magnetoresistance (MR) and a broadened MR transition. An La0.7Ca0.3MnO3 (55 Å)/SrTiO3 (160 Å) superlattice shows 61% MR at 0.5 T and 109 K, defined by [R(0 T)−R(0.5 T)]/R(0 T), compared to 38% MR for a single layer La0.7Ca0.3MnO3 film at 125 K. MR of larger than 85% at 5 T has been observed in a broad temperature range (from 150 to 10 K) for this superlattice. A systematic study of La0.7Ba0.3MnO3/SrTiO3 superlattices shows that the decrease of the La0.7Ba0.3MnO3 layer thickness results in the broadening of the MR peak in temperature.