Enhanced THz emission from spintronic Fe/Pt emitters through crystal growth optimization

Abstract

We investigate the THz emission characteristics of ferromagnetic/non-magnetic metallic heterostructures, focusing on thin Fe/Pt bilayers. In particular, we report on the impact of optimized crystal growth of the epitaxial Fe layers on the THz emission amplitude and spectral bandwidth. We demonstrate an enhancement of the emitted intensity along with an expansion of the emission bandwidth. Both are related to reduced spin scattering and higher interface transmission. Our work provides a pathway for devicing optimal spintronic THz emitters based on epitaxial Fe. It also highlights how THz emission measurements can be utilized to characterize the changes in out-of-equilibrium spin current dynamics in metallic heterostructures, driven by subtle structural refinement.

Influence of misfit strain on the physical properties of Fe thin films

“…The growth of thin Fe layers on MgAl 2 O 4 has been shown to result in a better crystal quality of the Fe layers, as compared to when grown on MgO 16 . This has been used for investigations of the effects of crystal quality on Gilbert damping 16 , THz emission 17,18 as well as on the magnetic properties of Fe in Fe/MgAl 2 O 4 /Fe (001) 15,[19][20][21][22] . Crystalline Fe has a fourfold in-plane magnetocrystalline anisotropy.…”

Ultrafast spin-currents and charge conversion at 3d-5d interfaces probed by time-domain terahertz spectroscopy

“…The process efficiency scales now with the electronic transmission, characterized as the spin-mixing conductance of the considered interface 40,46 . The combination of SP-ISHE and THz techniques thus offers the ability to analyze the anatomy of spin-current injection in TM based multilayers from which the electronic transmission appears to be the key physical parameter 39,40,[47][48][49] as discussed very recently in the analysis of THz emission from spintronic emitters 51,72 . Moreover, very recent experiments of SCC by FMR spin-pumping/ISHE methods foresees possible breakthrough for THz emission supplied by Rashba-states exhibiting IEE characteristic lengths of 6 nm 52 , thus largely exceeding the one of Co/Pt.…”