Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSpin relaxation signature of colossal magnetic anisotropy in platinum atomic chains
65
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Recent experimental data demonstrate emerging magnetic order in platinum atomically thin nanowires. Furthermore, an unusual form of magnetic anisotropy -- colossal magnetic anisotropy (CMA) -- was earlier predicted to exist in atomically thin platinum nanowires. Using spin dynamics simulations based on first-principles calculations, we here explore the spin dynamics of atomically thin platinum wires to reveal the spin relaxation signature of colossal magnetic anisotropy, comparing it with other types of anisotropy such as uniaxial magnetic anisotropy (UMA). We find that the CMA alters the spin relaxation process distinctly and, most importantly, causes a large speed-up of the magnetic relaxation compared to uniaxial magnetic anisotropy. The magnetic behavior of the nanowire exhibiting CMA should be possible to identify experimentally at the nanosecond time scale for temperatures below 5 K. This time-scale is accessible in e.g., soft x-ray free electron laser experiments.
rate research
Read More
The Fermi-surfaces and Elliott-Yafet spin-mixing parameter (EYP) of several elemental metals are studied by emph{ab initio} calculations. We focus first on the anisotropy of the EYP as a function of the direction of the spin-quantization axis [Phys.~Rev.~Lett. textbf{109}, 236603 (2012)]. We analyze in detail the origin of the gigantic anisotropy in $5d$ hcp metals as compared to $5d$ cubic metals by band-structure calculations and discuss the stability of our results against an applied magnetic field. We further present calculations of light (4$d$ and 3$d$) hcp crystals, where we find a huge increase of the EYP anisotropy, reaching colossal values as large as $6000%$ in hcp Ti. We attribute these findings to the reduced strength of spin-orbit coupling, which promotes the anisotropic spin-flip hot loops at the Fermi surface. In order to conduct these investigations, we developed an adapted tetrahedron-based method for the precise calculation of Fermi surfaces of complicated shape and accurate Fermi-surface integrals within the full-potential relativistic Korringa-Kohn-Rostoker Green-function method.
Using first principles simulations we perform a detailed study of the structural, electronic and transport properties of monoatomic platinum chains, sandwiched between platinum electrodes. First we demonstrate that the most stable atomic configuration corresponds to a zigzag arrangement that gradually straightens as the chains are stretched. Secondly, we find that the conductance at equilibrium atomic spacing does not oscillate with the number of atoms $n$ in the chain, but instead decreases almost monotonically with $n$. In contrast, the conductances of chains of fixed $n$ oscillate as the end atoms are pulled apart, due to the gradual closing and opening of conductance channels as the chain straightens.
Metal atomic chains have been reported to change their electronic or magnetic properties by slight mechanical stimulus. However, the mechanical response has been veiled because of lack of information on the bond nature. Here, we clarify the bond nature in platinum (Pt) monatomic chains by our developed in-situ transmission electron microscope method. The stiffness is measured with sub N/m precision by quartz length-extension resonator. The bond stiffnesses at the middle of the chain and at the connecting to the base are estimated to be 25 and 23 N/m, respectively, which are higher than the bulk counterpart. Interestingly, the bond length of 0.25 nm is found to be elastically stretched to 0.31 nm, corresponding to 24% in strain. Such peculiar bond nature could be explained by a novel concept of string tension. This study is a milestone that will significantly change the way we think about atomic bonds in one-dimensional substance.
We have fabricated oxide based spin filter junctions in which we demonstrate that magnetic anisotropy can be used to tune the transport behavior of spin filter junctions. Until recently, spin filters have been largely comprised of polycrystalline materials where the spin filter barrier layer and one of the electrodes are ferromagnetic. These spin filter junctions have relied on the weak magnetic coupling between one ferromagnetic electrode and a barrier layer or the insertion of a nonmagnetic insulating layer in between the spin filter barrier and electrode. We have demonstrated spin filtering behavior in La0.7Sr0.3MnO3/chromite/Fe3O4 junctions without nonmagnetic spacer layers where the interface anisotropy plays a significant role in determining transport behavior. Detailed studies of chemical and magnetic structure at the interfaces indicate that abrupt changes in magnetic anisotropy across the non-isostructural interface is the cause of the significant suppression of junction magnetoresistance in junctions with MnCr2O4 barrier layers.
Spin transfer torque (STT) driven by a charge current plays a key role in magnetization switching in heavy-metal/ferromagnetic-metal structures. The STT efficiency defined by the ratio between the effective field due to STT and the current density, is required to be improved to reduce energy compulsions in the STT-based spintronic devices. In this work, using the harmonic Hall measurement method, we experimentally studied the STT efficiency in platinum(Pt)/FM structures as a function of the Pt thickness. We found that the STT efficiency strongly depends on the Pt thickness and reaches a maximum value of 4.259 mT/($10^6$A/$cm^{2}$) for the 1.8-nm-thickness Pt sample. This result indicates that competition between spin Hall effect (SHE) and Rashba effect as well as spin diffusion process across the Pt layer determines the Pt thickness for the maximum STT efficiency. We demonstrated the role played by the spin diffusion besides the spin current generation mechanisms in improvement of the STT efficiency, which is helpful in designing STT-based devices.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
