3 research outputs found
Field-Free Switching of Perpendicular Magnetization in an Ultrathin Epitaxial Magnetic Insulator
For energy-efficient magnetic memories, switching of
perpendicular
magnetization by spinâorbit torque (SOT) appears to be a promising
solution. This SOT switching requires the assistance of an in-plane
magnetic field to break the symmetry. Here, we demonstrate the field-free
SOT switching of a perpendicularly magnetized thulium iron garnet
(Tm3Fe5O12, TmIG). The polarity of
the switching loops, clockwise or counterclockwise, is determined
by the direction of the initial current pulses, in contrast with field-assisted
switching where the polarity is controlled by the direction of the
magnetic field. From Brillouin light scattering, we determined the
DzyaloshinskiiâMoriya interaction (DMI) induced by the PtâTmIG
interface. We will discuss the possible origins of field-free switching
and the roles of the interfacial DMI and cubic magnetic anisotropy
of TmIG. This discussion is substantiated by magnetotransport, Kerr
microscopy, and micromagnetic simulations. Our observation of field-free
electrical switching of a magnetic insulator is an important milestone
for low-power spintronic devices
Ultrahigh carrier mobilities in ferroelectric domain wall Corbino cones at room temperature
Recently, electrically conducting heterointerfaces between dissimilar band insulators (such as lanthanum aluminate and strontium titanate) have attracted considerable research interest. Charge transport and fundamental aspects of conduction have been thoroughly explored. Perhaps surprisingly, similar studies on conceptually much simpler conducting homointerfaces, such as domain walls, are not nearly so well developed. Addressing this disparity, magnetoresistance is herein reported in approximately conical 180°charged domain walls, in partially switched ferroelectric thin-film single?crystal lithium niobate. This system is ideal for such measurements: first, the conductivity difference between domains and domain walls is unusually large (a factor of 1013) and hence currents driven through the thin film, between planar top and bottom electrodes, are overwhelmingly channeled along the walls; second, when electrical contact is made to the top and bottom of the domain walls and a magnetic field is applied along their cone axes, then the test geometry mirrors that of a Corbino disk: a textbook arrangement for geometric magnetoresistance measurement. Data imply carriers with extremely high room-temperature Hall mobilities of up to â3700 cm2  Vâ1  sâ1. This is an unparalleled value for oxide interfaces (and for bulk oxides) comparable to mobilities in other systems seen at cryogenic, rather than at room, temperature.</p
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