An official website of the United States government
Magnetic properties and interfacial phenomena of epitaxial perovskite oxides depend sensitively on parameters such as film thickness and strain state. In this work, epitaxial La 0.67 Sr 0.33 CoO 3 (LSCO)/La 0.67 Sr 0.33 MnO 3 (LSMO) bilayers were grown on NdGaO 3 (NGO) and LaAlO 3 (LAO) substrates with a fixed LSMO thickness of 6 nm, and LSCO thickness (t LSCO ) varying from 2 to 10 nm. Soft x-ray magnetic spectroscopy revealed that magnetically active Co 2+ ions that strongly coupled to the LSMO layer were observed below a critical t LSCO for bilayers grown on both substrates. On LAO substrates, this critical thickness was 2 nm, above which the formation of Co 2+ ions was quickly suppressed leaving only a soft LSCO layer with mixed valence Co 3+ /Co 4+ ions. The magnetic properties of both LSCO and LSMO layers displayed strong t LSCO dependence. This critical t LSCO increased to 4 nm on NGO substrates, and the magnetic properties of only the LSCO layer displayed t LSCO dependence. A non-magnetic layer characterized by Co 3+ ions and with a thickness below 2 nm exists at the LSCO/substrate interface for both substrates. The results contribute to the understanding of interfacial exchange spring behavior needed for applications in next generation spintronic and magnetic memory devices.
more »
« less
This content will become publicly available on May 1, 2026
Exchange Bias in La 0.67 Sr 0.33 MnO 3 /YFeO 3 Ferromagnet/Antiferromagnet Multilayer Heterostructures
Abstract Exchange bias (EB), manifested as a hysteresis‐loop offset after field‐cooling, is demonstrated in perovskite‐structured ferromagnet/antiferromagnet (La0.67Sr0.33MnO3/YFeO3)nheterostructures grown on (100) SrTiO3substrates. Bilayer samples show an EB of 306 Oe at 50 K, whereas multilayers with five layers exhibit an exchange bias of up to 424 Oe at 50 K. A spin valve consisting of La0.67Sr0.33MnO3/SrTiO3/La0.67Sr0.33MnO3/YFeO3shows stable remanent configurations resulting from pinning of the upper La0.67Sr0.33MnO3layer by the YFeO3. In contrast, EB is not observed on (111)‐oriented SrTiO3substrates due to interface roughening. These results demonstrate YFeO3as an alternative orthoferrite antiferromagnet compared to BiFeO3and LaFeO3for incorporation into exchange‐biased heterostructures.
more »
« less
- PAR ID:
- 10625644
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Small
- Volume:
- 21
- Issue:
- 21
- ISSN:
- 1613-6810
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The superior size and power scaling potential of ferroelectric-gated Mott transistors makes them promising building blocks for developing energy-efficient memory and logic applications in the post-Moore’s Law era. The close to metallic carrier density in the Mott channel, however, imposes the bottleneck for achieving substantial field effect modulation via a solid-state gate. Previous studies have focused on optimizing the thickness, charge mobility, and carrier density of single-layer correlated channels, which have only led to moderate resistance switching at room temperature. Here, we report a record high nonvolatile resistance switching ratio of 38,440% at 300 K in a prototype Mott transistor consisting of a ferroelectric PbZr0.2Ti0.8O3gate and anRNiO3(R: rare earth)/La0.67Sr0.33MnO3composite channel. The ultrathin La0.67Sr0.33MnO3buffer layer not only tailors the carrier density profile inRNiO3through interfacial charge transfer, as corroborated by first-principles calculations, but also provides an extended screening layer that reduces the depolarization effect in the ferroelectric gate. Our study points to an effective material strategy for the functional design of complex oxide heterointerfaces that harnesses the competing roles of charge in field effect screening and ferroelectric depolarization effects.more » « less
-
null (Ed.)A new two-phase BaTiO 3 : La 0.7 Sr 0.3 MnO 3 nanocomposite system with a molar ratio of 8 : 2 has been grown on single crystal SrTiO 3 (001) substrates using a one-step pulsed laser deposition technique. Vertically aligned nanocomposite thin films with ultra-thin La 0.7 Sr 0.3 MnO 3 pillars embedded in the BaTiO 3 matrix have been obtained and the geometry of the pillars varies with deposition frequency. The room temperature multiferroic properties, including ferromagnetism and ferroelectricity, have been demonstrated. Anisotropic ferromagnetism and dielectric constants have been observed, which can be tuned by deposition frequencies. The tunable anisotropic optical properties originated from the conducting pillars in the dielectric matrix structure, which cause different electron transport paths. In addition, tunable band gaps have been discovered in the nanocomposites. This multiferroic and anisotropic system has shown its great potentials towards multiferroics and non-linear optics.more » « less
-
Abstract BaTiO3heated in an excess of SrCl2at 1150 °C converts to SrTiO3through an ion exchange reaction. The SrTiO3synthesized by ion exchange produces hydrogen from pH 7 water at a rate more than twice that of conventional SrTiO3treated identically. The apparent quantum yield for hydrogen production in pure water of the ion exchanged SrTiO3is 11.4% under 380 nm illumination. The catalyst resulting from ion‐exchange differs from conventional SrTiO3by having ≈2% residual Ba, inhomogeneous Cl‐doping at a concentration less than 1%, Kirkendall voids in the centers of particles that result from the unequal rates of Sr and Ba diffusion together with the transport of Ti and O, and nanoscale regions near the surface that have lattice spacings consistent with the Sr‐excess phase Sr2TiO4. The increased photochemical efficiency of this nonequilibrium structure is most likely related to the Sr‐excess, which is known to compensate donor defects that can act as charge traps and recombination centers.more » « less
-
Abstract Ultrathin epitaxial films of ferromagnetic insulators (FMIs) with Curie temperatures near room temperature are critically needed for use in dissipationless quantum computation and spintronic devices. However, such materials are extremely rare. Here, a room‐temperature FMI is achieved in ultrathin La0.9Ba0.1MnO3films grown on SrTiO3substrates via an interface proximity effect. Detailed scanning transmission electron microscopy images clearly demonstrate that MnO6octahedral rotations in La0.9Ba0.1MnO3close to the interface are strongly suppressed. As determined from in situ X‐ray photoemission spectroscopy, OK‐edge X‐ray absorption spectroscopy, and density functional theory, the realization of the FMI state arises from a reduction of Mn egbandwidth caused by the quenched MnO6octahedral rotations. The emerging FMI state in La0.9Ba0.1MnO3together with necessary coherent interface achieved with the perovskite substrate gives very high potential for future high performance electronic devices.more » « less
