4 research outputs found
Gradient-Induced Dzyaloshinskii–Moriya Interaction
The Dzyaloshinskii–Moriya interaction (DMI) that
arises
in the magnetic systems with broken inversion symmetry plays an essential
role in topological spintronics. Here, by means of atomistic spin
calculations, we study an intriguing type of DMI (g-DMI) that emerges
in the films with composition gradient. We show that both the strength
and chirality of g-DMI can be controlled by the composition gradient
even in the disordered system. The layer-resolved analysis of g-DMI
unveils its additive nature inside the bulk layers and clarifies the
linear thickness dependence of g-DMI observed in experiments. Furthermore,
we demonstrate the g-DMI-induced chiral magnetic structures, such
as spin spirals and skyrmions, and the g-DMI driven field-free spin–orbit
torque (SOT) switching, both of which are crucial toward practical
device application. These results elucidate the underlying mechanisms
of g-DMI and open up a new way to engineer the topological magnetic
textures
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
Field-Free Switching of Perpendicular Magnetization in an Ultrathin Epitaxial Magnetic Insulator
For energy-efficient magnetic memories, switching of
perpendicular
magnetization by spin–orbit 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
Dzyaloshinskii–Moriya interaction (DMI) induced by the Pt–TmIG
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
Bilinear magnetoresistance in HgTe topological insulator: opposite signs at opposite surfaces demonstrated by gate control
Abstract Spin-orbit effects appearing in topological insulators (TI) and at Rashba interfaces are currently revolutionizing how we can manipulate spins and have led to several newly discovered effects, from spin-charge interconversion and spin-orbit torques to novel magnetoresistance phenomena. In particular, a puzzling magnetoresistance has been evidenced, bilinear in electric and magnetic fields. Here, we report the observation of bilinear magnetoresistance (BMR) in strained HgTe, a prototypical TI. We show that both the amplitude and sign of this BMR can be tuned by controling, with an electric gate, the relative proportions of the opposite contributions of opposite surfaces. At magnetic fields of 1 T, the magnetoresistance is of the order of 1 \% and has a larger figure of merit than previously measured TIs. We propose a theoretical model giving a quantitative account of our experimental data. This phenomenon, unique to TI, offer novel opportunities to tune the electrical response of surface states for spintronics