All‐Optical Detection of Spin Pumping and Giant Interfacial Spin Transparency in Co₂Fe_0.4Mn_0.6Si/Pt Heterostructure

Abstract

Active control over the generation and manipulation of pure spin current has propelled drastic transformation in new generation spintronics. Spin pumping is one of the favored mechanisms to generate pure spin current and its efficiency can be parameterized in terms of spin-mixing conductance (G ↑↓ ) and spin-diffusion length (𝝀). Here, using all-optical time-resolved magneto-optical Kerr magnetometry, spin pumping in a ferromagnetic Heusler compound (Co 2 Fe 0.4 Mn 0.6 Si (CFMS))/Pt heterostructure is investigated keeping in mind the small intrinsic damping and stable spin-polarized band structure at the Fermi level of the CFMS and excellent spin-sink property of Pt. The thickness-dependent evolution of Gilbert damping is modeled using ballistic and diffusive spin transport frameworks to extract G ↑↓ and 𝝀. Finally, a giant value of interfacial spin transparency up to 0.87 ± 0.02 combined with small intrinsic damping of 0.0039 ± 0.0004 promote the CFMS/Pt heterostructure as a champion material for the development of advanced spin-orbitronic devices.

All-optical observation of giant spin transparency at the topological insulator BiSbTe1.5Se1.5/Co20Fe60B20 interface

“…As shown in Fig. 3b, the effective damping in the presence of the BSTS underlayer was found to show a nonmonotonic variation consisting of a sharp enhancement in α eff from its intrinsic value of 0.0084 to a saturating value of 0.0114 at high values of t. The observed dependence is a characteristic signature of spin pumping, showing a similar nature to those reported in various systems involving ferromagnetic thin films interfaced with a topologically trivial NM 29,30,62 . However, this dependence is not immediately expected in topological systems where the spin-to-charge conversion efficiency in several spin pumping experiments has been attributed to a dominant role played by the topologically protected surface states 23,72 , whose thicknesses do not vary with the film thickness.…”

“…However, while the modulation due to SML scales inversely with FM thickness similar to spin pumping, that due to TMS scales quadratically, making it possible to straightforwardly isolate its contribution from FM-thickness-dependent measurements of the damping. The total damping modulation arising due to the combined effect of spin pumping and TMS can be expressed as 61,62 :…”

“…( 9) to be a very high value of 0.9 in the so-called "perfect spin-sink" regime t »λ s when the BSTS thickness dependence of the damping modulation saturates 54 , leading to a high effective spin-mixing conductance of the BSTS/CoFeB interface. Thus, high values of T are attainable in BSTS/FM systems, which provides another dimension to their applicability for pure spin-current-based spintronic devices 30,62 . The strong bulk SOC of the BSTS topological insulator allows easier spin current dissipation 52 , resulting in a high G eff value and a high interfacial spin transparency.…”

Large enhancement of magnetic damping in half-metallic Co2MnSi Heusler alloy thin films with heavy metal Pt layer observed by the all-optical method

“…18,19) Therefore, spin current evaluation in the FM/HM heterostructure has been investigated by using the all-optical method. [20][21][22][23] Half-metallic Heusler alloy is technologically an important material because of its high spin polarization at Fermi level. Co 2 MnSi (CMS) has been chosen among them as a standard half-metallic Heusler alloy due to its high Curie temperature and large band gap for the minority spin band.…”

Heavy metal deposition temperature tuned spin pumping efficiency control in permalloy/tantalum bilayers

“…Heterostructures comprising of bilayers of ferromagnet (FM) and heavy metal (HM) are of immense significance in spintronics as they allow realization of various useful phenomenon related to conversion of spin current to charge current and their reciprocal effects [1][2][3][4][5][6][7]. Especially FM/HM bilayers provide an ideal platform for generation of pure spin current via spin pumping without requiring flow of charge current [3,[8][9][10]. This opens up immense opportunity for spintronics based low power device applications [11,12].…”