59 research outputs found
Evidence for lattice-polarization-enhanced field effects at the SrTiO<sub>3</sub>-based heterointerface
Electrostatic gating provides a powerful approach to tune the conductivity of the two-dimensional electron liquid between two insulating oxides. For the LaAlO(3)/SrTiO(3) (LAO/STO) interface, such gating effect could be further enhanced by a strong lattice polarization of STO caused by simultaneous application of gate field and illumination light. Herein, by monitoring the discharging process upon removing the gate field, we give firm evidence for the occurrence of this lattice polarization at the amorphous-LaAlO(3)/SrTiO(3) interface. Moreover, we find that the lattice polarization is accompanied with a large expansion of the out-of-plane lattice of STO. Photo excitation affects the polarization process by accelerating the field-induced lattice expansion. The present work demonstrates the great potential of combined stimuli in exploring emergent phenomenon at complex oxide interfaces
Diluted Oxide Interfaces with Tunable Ground States
The metallic interface between two oxide insulators, such as LaAlO3/SrTiO3
(LAO/STO), provides new opportunities for electronics and spintronics. However,
due to the presence of multiple orbital populations, tailoring the interfacial
properties such as the ground state and metal-insulator transitions remains
challenging. Here, we report an unforeseen tunability of the phase diagram of
LAO/STO by alloying LAO with a ferromagnetic LaMnO3 insulator without forming
lattice disorder and at the same time without changing the polarity of the
system. By increasing the Mn-doping level, x, of LaAl1-xMnxO3/STO, the
interface undergoes a Lifshitz transition at x = 0.225 across a critical
carrier density of nc= 2.8E13 cm-2, where a peak TSC =255 mK of superconducting
transition temperature is observed. Moreover, the LaAl1-xMnxO3 turns
ferromagnetic at x >=0.25. Remarkably, at x = 0.3, where the metallic interface
is populated by only dxy electrons and just before it becomes insulating, we
achieve reproducibly a same device with both signatures of superconductivity
and clear anomalous Hall effect. This provides a unique and effective way to
tailor oxide interfaces for designing on-demand electronic and spintronic
devices.Comment: 18 pages and 6 figure
Scaling of Berry-curvature monopole dominated large linear positive magnetoresistance
The linear positive magnetoresistance (LPMR) is a widely observed phenomenon
in topological materials, which is promising for potential applications on
topological spintronics. However, its mechanism remains ambiguous yet and the
effect is thus uncontrollable. Here, we report a quantitative scaling model
that correlates the LPMR with the Berry curvature, based on a ferromagnetic
Weyl semimetal CoS2 that bears the largest LPMR of over 500% at 2 Kelvin and 9
Tesla, among known magnetic topological semimetals. In this system, masses of
Weyl nodes existing near the Fermi level, revealed by theoretical calculations,
serve as Berry-curvature monopoles and low-effective-mass carriers. Based on
the Weyl picture, we propose a relation , with B being the applied magnetic field and the average Berry curvature near the Fermi surface, and further
introduce temperature factor to both MR/B slope (MR per unit field) and
anomalous Hall conductivity, which establishes the connection between the model
and experimental measurements. A clear picture of the linearly slowing down of
carriers, i.e., the LPMR effect, is demonstrated under the cooperation of the
k-space Berry curvature and real-space magnetic field. Our study not only
provides an experimental evidence of Berry curvature induced LPMR for the first
time, but also promotes the common understanding and functional designing of
the large Berry-curvature MR in topological Dirac/Weyl systems for magnetic
sensing or information storage
Metallic Conduction and Ferromagnetism in MAl<sub>2</sub>O<sub>4</sub>/SrTiO<sub>3</sub> Spinel/Perovskite Heterostructures (M=Fe, Co, Ni)
Operational test of bonded magnetocaloric plates
Bonded plates made by hot pressing La0.85Ce0.15Fe11.25Mn0.25Si1.5Hy particles and resin have been tested as active magnetic regenerators in a small scale magnetocaloric device. Firstly the plates were carefully characterised magnetically and thermally. The plates were prepared with 5 wt% resin, and from density measurements it was found that the volume ratio of the magnetocaloric material in the plates was 0.53, due to the resin and porosity. The best operating conditions for the plate regenerator were determined at which a temperature span of 6.4 K was measured along the plates
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