Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSpin effects induced by thermal perturbation in a normal metal/magnetic insulator system
239
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Using one of the methods of quantum nonequilibrium statistical physics we have investigated the spin transport transverse to the normal metal/ferromagnetic insulator interface in hybrid nanostructures. An approximation of the effective parameters, when each of the interacting subsystems (electron spin, magnon, and phonon) is characterized by its own effective temperature have been considered. The generalized Bloch equations which describe the spin-wave current propagation in the dielectric have been derived. Finally, two sides of the spin transport coin have been revealed: the diffusive nature of the magnon motion and magnon relaxation processes, responsible for the spin pumping and the spin-torque effect.
rate research
Read More
We consider the influence of a spin accumulation in a normal metal on the magnetic statics and dynamics in an adjacent magnetic insulator. In particular, we focus on arbitary angles between the spin accumulation and the easy-axis of the magnetic insulator. Based on Landau-Lifshitz-Gilbert phenomenology supplemented with magnetoelectronic circuit theory, we find that the magnetic texture twists into a stable configuration that turns out to be described by a virtual, or image, domain wall configuration, i.e., a domain wall outside the ferromagnet. We show that even when the spin accumulation is perpendicular to the anisotropy axis, the magnetic texture develops a component parallel to the spin accumulation for sufficiently large spin bias. The emergence of this parallel component gives rise to threshold behavior in the spin Hall magnetoresistance and nonlocal magnon transport. This threshold can be used to design novel spintronic and magnonic devices that can be operated without external magnetic fields.
Pure spin currents, i.e. the transport of angular momentum without an accompanying charge current, represent a new, promising avenue in modern spintronics from both a fundamental and an application point of view. Such pure spin currents can not only flow in electrical conductors via mobile charge carriers, but also in magnetically ordered electrical insulators as a flow of spin excitation quanta. Over the course of the last years remarkable results have been obtained in heterostructures consisting of magnetically ordered insulators interfaced with a normal metal, where a pure spin current flows across the interface. This topical review article deals with the fundamental principles, experimental findings and recent developments in the field of pure spin currents in magnetically ordered insulators. We here put our focus onto four different manifestations of pure spin currents in such heterostructures: The spin pumping effect, the longitudinal spin Seebeck effect, the spin Hall magnetoresistance and the all-electrical detection of magnon transport in non-local device concepts. In this article, we utilize a common theoretical framework to explain all four effects and explain important material systems (especially rare-earth iron garnets) used in the experiments. For each effect we introduce basic measurement techniques and detection schemes and discuss their application in the experiment. We account for the remarkable progress achieved in each field by reporting the recent progress in each field and by discussing research highlights obtained in our group. Finally, we conclude the review article with an outlook on future challenges and obstacles in the field of pure spin currents in magnetically ordered insulator / normal metal heterostructures.
A metal-insulator transition was induced by in-plane magnetic fields up to 27 T in homogeneously Sb-doped Si/SiGe superlattice structures. The localisation is not observed for perpendicular magnetic fields. A comparison with magnetoconductivity investigations in the weakly localised regime shows that the delocalising effect originates from the interaction-induced spin-triplet term in the particle-hole diffusion channel. It is expected that this term, possibly together with the singlet particle-particle contribution, is of general importance in disordered n-type Si bulk and heterostructures.
Recent experiments demonstrating large spin-transfer torques in topological insulator (TI)-ferromagnetic metal (FM) bilayers have generated a great deal of excitement due to their potential applications in spintronics. The source of the observed spin-transfer torque, however, remains unclear. This is because the large charge transfer from the FM to TI layer would prevent the Dirac cone at the interface from being anywhere near the Fermi level to contribute to the observed spin-transfer torque. Moreover, there is yet little understanding of the impact on the Dirac cone at the interface from the metallic bands overlapping in energy and momentum, where strong hybridization could take place. Here, we build a simple microscopic model and perform first-principles-based simulations for such a TI-FM heterostructure, considering the strong hybridization and charge transfer effects. We find that the original Dirac cone is destroyed by the hybridization as expected. Instead, we find a new interface state which we dub descendent state to form near the Fermi level due to the strong hybridization with the FM states at the same momentum. Such a `descendent state carries a sizable weight of the original Dirac interface state, and thus inherits the localization at the interface and the same Rashba-type spin-momentum locking. We propose that the `descendent state may be an important source of the experimentally observed large spin-transfer torque in the TI-FM heterostructure.
Spin-dependent transport at heavy metal/magnetic insulator interfaces is at the origin of many phenomena at the forefront of spintronics research. A proper quantification of the different interfacial spin conductances is crucial for many applications. Here, we report the first measurement of the spin Hall magnetoresistance (SMR) of Pt on a purely ferromagnetic insulator (EuS). We perform SMR measurements in a wide range of temperatures and fit the results by using a microscopic model. From this fitting procedure we obtain the temperature dependence of the spin conductances ($G_s$, $G_r$ and $G_i$), disentangling the contribution of field-like torque ($G_i$), damping-like torque ($G_r$), and spin-flip scattering ($G_s$). An interfacial exchange field of the order of 1 meV acting upon the conduction electrons of Pt can be estimated from $G_i$, which is at least three times larger than $G_r$ below the Curie temperature. Our work provides an easy method to quantify this interfacial spin-splitting field, which play a key role in emerging fields such as superconducting spintronics and caloritronics, and topological quantum computation.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
