3 research outputs found
Self-Assembled Monolayer-Functionalized Half-Metallic Manganite for Molecular Spintronics
(La,Sr)MnO<sub>3</sub> manganite (LSMO) has emerged as the standard ferromagnetic electrode in organic spintronic devices due to its highly spin-polarized character and air stability. Whereas organic semiconductors and polymers have been mainly envisaged to propagate spin information, self-assembled monolayers (SAMs) have been overlooked and should be considered as promising materials for molecular engineering of spintronic devices. Surprisingly, up to now the first key step of SAM grafting protocols over LSMO surface thin films is still missing. We report the grafting of dodecyl (C12P) and octadecyl (C18P) phosphonic acids over the LSMO half-metallic oxide. Alkylphosphonic acids form ordered self-assembled monolayers, with the phosphonic group coordinated to the surface and alkyl chains tilted from the surface vertical by 43° (C12P) and 27° (C18P). We have electrically characterized these SAMs in nanodevices and found that they act as tunnel barriers, opening the door toward the integration of alkylphosphonic acid//LSMO SAMs into future molecular/organic spintronic devices such as spin OLEDs
Atomic and Electronic Structure of the BaTiO<sub>3</sub>/Fe Interface in Multiferroic Tunnel Junctions
Artificial multiferroic tunnel junctions combining a
ferroelectric
tunnel barrier of BaTiO<sub>3</sub> with magnetic electrodes display
a tunnel magnetoresistance whose intensity can be controlled by the
ferroelectric polarization of the barrier. This effect, called tunnel
electromagnetoresistance (TEMR), and the corollary magnetoelectric
coupling mechanisms at the BaTiO<sub>3</sub>/Fe interface were recently
reported through macroscopic techniques. Here, we use advanced spectromicroscopy
techniques by means of aberration-corrected scanning transmission
electron microscopy (STEM) and electron energy-loss spectroscopy (EELS)
to probe locally the nanoscale structural and electronic modifications
at the ferroelectric/ferromagnetic interface. Atomically resolved
real-space spectroscopic techniques reveal the presence of a single
FeO layer between BaTiO<sub>3</sub> and Fe. Based on this accurate
description of the studied interface, we propose an atomistic model
of the ferroelectric/ferromagnetic interface further validated by
comparing experimental and simulated STEM images with atomic resolution.
Density functional theory calculations allow us to interpret the electronic
and magnetic properties of these interfaces and to understand better
their key role in the physics of multiferroics nanostructures
Onset of Multiferroicity in Prototypical Single-Spin Cycloid BiFeO<sub>3</sub> Thin Films
In the room-temperature magnetoelectric multiferroic
BiFeO3, the noncollinear antiferromagnetic state is coupled
to the
ferroelectric order, opening applications for low-power electric-field-controlled
magnetic devices. While several strategies have been explored to simplify
the ferroelectric landscape, here we directly stabilize a single-domain
ferroelectric and spin cycloid state in epitaxial BiFeO3 (111) thin films grown on orthorhombic DyScO3 (011).
Comparing them with films grown on SrTiO3 (111), we identify
anisotropic in-plane strain as a powerful handle for tailoring the
single antiferromagnetic state. In this single-domain multiferroic
state, we establish the thickness limit of the coexisting electric
and magnetic orders and directly visualize the suppression of the
spin cycloid induced by the magnetoelectric interaction below the
ultrathin limit of 1.4 nm. This as-grown single-domain multiferroic
configuration in BiFeO3 thin films opens an avenue both
for fundamental investigations and for electrically controlled noncollinear
antiferromagnetic spintronics