Evidence for Dyakonov-Perel-like Spin Relaxation in Pt

Abstract

We utilize nanoscale spin valves with Pt spacer layers to characterize spin scattering in Pt. Analysis of the spin lifetime determined from our measurements indicates that the extrinsic Elliot-Yafet spin scattering is dominant at room temperature, while the intrinsic Dyakonov-Perel mechanism dominates at cryogenic temperatures. The significance of the latter is supported by the suppression of spin relaxation in Pt layers interfaced with a ferromagnet, likely caused by the competition between the effective exchange and spin-orbit fields.The interplay between electron's motion and its spin due to the spin-orbit interaction (SOI) opens unprecedented opportunities for the control of both spin and orbital degrees of freedom [1][2][3][4][5]. For instance, the spin Hall effect (SHE) results in generation of pure spin current flowing transverse to charge current [6], enabling electronic control of static and dynamic states of magnetization in metallic and insulating nanomagnets [7][8][9]. Extensive recent studies of materials that exhibit large SOI, including Pt, Ta, W, topological insulators, and alloys such as CuBi, have focused on identifying the intrinsic and extrinsic mechanisms controlling SOI, and characterizing the relevant parameters including the spin-orbit scattering rates, the spin Hall angle, and the effective spin-orbit field [10][11][12][13][14][15][16][17]. Another relevant parameter is the spin diffusion length λ, defined as the length scale over which the spin polarization relaxes away from the external source, which is determined mostly by the spin scattering due to SOI. It is also the length scale for spin current generation via the SHE, and is thus directly related to material's performance in spin-Hall applications.Pt is one of the most extensively studied spin-orbit materials, thanks to the large SOI effects [10,18,19], relatively low resistivity that minimizes Joule heating and current shunting in heterostructures, and low reactivity. A variety of approaches have been utilized to determine the parameters relevant to SOI in Pt such as the spin Hall angle and λ [10,14,18,[20][21][22]. Nevertheless, the values and the mechanisms controlling these parameters are still debated. In particular, the reported values of the spin Hall angle in Pt range from 0.004 to over 0.1 [10,14,23], and those of λ range from less than 1 nm to over 10 nm [10,14,18,[20][21][22][24][25][26]. Such a large spread of the reported characteristics makes it challenging to establish the dominant contributions to spin-orbit effects and the mechanisms controlling them.One of the main difficulties in analyzing SOI is posed by the interplay between the interfacial and bulk effects. For instance, measurements of spin current generated by SHE are inevitably affected by the spin relaxation at the Pt interfaces, and by its generation via the interfacial Rashba effect [27]. Indeed, the apparent spin Hall angle has been shown to depend on the transparency of the interfaces [23]. Measurements of λ based on the spin absorption efficiency [21...

Spin diffusion length associated with out-of-plane conductivity of Pt in spin pumping experiments

“…Our work provides strong evidence that ρ ⊥ determines λ s and hence it does not depend on t NM . In addition, we show evidence of the low influence of temperature in τ s of Pt, in agreement with recently reported results [11].…”

“…Moreover, the spin-flip scattering mechanisms that determine λ s are not completely understood. It has been generally assumed that the Elliot-Yaffet (EY) mechanism is the dominant mechanism in Pt; however, recent results have shown that both the Dyakonov-Perel (DP) and EY spin relaxation mechanisms coexist at low temperatures [11].…”

Generation of pure superconducting spin current in magnetic heterostructures via nonlocally induced magnetism due to Landau Fermi liquid effects

“…In Nb, the spin diffusion length has been estimated at λ Nb sd = 48 nm 47,86 . The spin diffusion length in Pt, λ Pt sd , is difficult to determine unambiguously because of the presence of SOC 98 , however the range of values is 1nm < λ Pt sd < 14nm [98][99][100] . Moreover, this spin diffusion length is expected to vary with the Pt layer thickness 100 .…”

Femtosecond formation dynamics of the spin Seebeck effect revealed by terahertz spectroscopy

“…It is still an open question how the SSE current j s evolves for fast temperature variations and in the presence of nonthermal states. Insights into these points are crucial to reveal the role of elementary processes in the formation of the SSE current, for instance magnon creation 12 in F and spin relaxation 13 in N. The high-frequency behavior of the SSE is also relevant for applications, such as magnetization control by terahertz (THz) spin currents 14 – 16 and spintronic THz-radiation sources 17 – 21 .…”