Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA journey into the tuneable antiferromagnetic spin textures of BiFeO3
263
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Antiferromagnetic thin films are currently generating considerable excitement for low dissipation magnonics and spintronics. However, while tuneable antiferromagnetic textures form the backbone of functional devices, they are virtually unknown at the submicron scale. Here we image a wide variety of antiferromagnetic spin textures in multiferroic BiFeO3 thin films that can be tuned by strain and manipulated by electric fields through room temperature magnetoelectric coupling. Using piezoresponse force microscopy and scanning NV magnetometry in self-organized ferroelectric patterns of BiFeO3, we reveal how strain stabilizes different types of non-collinear antiferromagnetic states (bulk-like and exotic spin cycloids) as well as collinear antiferromagnetic textures. Beyond these local-scale observations, resonant elastic X-ray scattering confirms the existence of both types of spin cycloids. Finally, we show that electric-field control of the ferroelectric landscape induces transitions either between collinear and non-collinear states or between different cycloids, offering perspectives for the design of reconfigurable antiferromagnetic spin textures on demand.
rate research
Read More
We report a Rashba spin splitting of a two-dimensional electron gas in the topological insulator Bi$_2$Se$_3$ from angle-resolved photoemission spectroscopy. We further demonstrate its electrostatic control, and show that spin splittings can be achieved which are at least an order-of-magnitude larger than in other semiconductors. Together these results show promise for the miniaturization of spintronic devices to the nanoscale and their operation at room temperature.
Spin-polarized currents play a key role in spintronics. Recently, it has been found that antiferromagnets with a non-spin-degenerate band structure can efficiently spin-polarize electric currents, even though their net magnetization is zero. Among the antiferromagnetic metals with magnetic space group symmetry supporting this functionality, the noncollinear antiferromagnetic antiperovskites ANMn$_3$ (A = Ga, Ni, Sn, and Pt) are especially promising. This is due to their high Neel temperatures and a good lattice match to perovskite oxide substrates, offering possibilities of high structural quality heterostructures based on these materials. Here, we investigate the spin polarization of antiferromagnetic ANMn$_3$ metals using first-principles density functional theory calculations. We find that the spin polarization of the longitudinal currents in these materials is comparable to that in widely used ferromagnetic metals, and thus can be exploited in magnetic tunnel junctions and spin transfer torque devices. Moreover, for certain film growth directions, the out-of-plane transverse spin currents with a giant charge-to-spin conversion efficiency can be achieved, implying that the ANMn$_3$ antiperovskites can be used as efficient spin sources. These properties make ANMn$_3$ compounds promising for application in spintronics.
Magnetocrystalline anisotropy is essential in the physics of antiferromagnets and commonly treated as a constant, not depending on an external magnetic field. However, we demonstrate that in CoO the anisotropy should necessarily depend on the magnetic field, which is shown by the spin Hall magnetoresistance of the CoO | Pt device. Below the Neel temperature CoO reveals a spin-flop transition at 240 K at 7.0 T, above which a hysteresis in the angular dependence of magnetoresistance unexpectedly persists up to 30 T. It is most likely due to the presence of the unquenched orbital momentum, which can play an important role in antiferromagnetic spintronics.
Recent studies have reported the existence of an epitaxially-stabilized tetragonal-like (T-like) monoclinic phase in BiFeO3 thin-films with high levels of compressive strain. While their structural and ferroelectric properties are different than those of rhombohedral-like (R-like) films with lower levels of strain, little information exists on magnetic properties. Here, we report a detailed neutron scattering study of a nearly phase-pure film of T-like BiFeO3. By tracking the temperature dependence and relative intensity of several superstructure peaks in the reciprocal lattice cell, we confirm antiferromagnetism with largely G-type character and TN = 324 K, significantly below a structural phase transition at 375 K, contrary to previous reports. Evidence for a second transition, possibly a minority magnetic phase with C-type character is also reported with TN = 260 K. The co-existence of the two magnetic phases in T-like BiFeO3 and the difference in ordering temperatures between R-like and T-like systems is explained through simple Fe-O-Fe bond distance considerations.
We investigate the impact of pinned antiferromagnetic order on the decoherence of spin current in polycrystalline IrMn. In NiFe/Cu/IrMn/CoFe multilayers, we coherently pump an electronic spin current from NiFe into IrMn, whose antiferromagnetic order is globally pinned by static exchange-bias coupling with CoFe. We observe no anisotropic spin decoherence with respect to the orientation of the pinned antiferromagnetic order. We also observe no difference in spin decoherence for samples with and without pinned antiferromagnetic order. Moreover, although there is a pronounced resonance linewidth increase in NiFe that coincides with the switching of IrMn/CoFe, we show that this is not indicative of anisotropic spin decoherence in IrMn. Our results demonstrate that the decoherence of electron-mediated spin current is remarkably insensitive to the magnetization state of the antiferromagnetic IrMn spin sink.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
