Co2FeAl Full Heusler Compound Based Spintronic Terahertz Emitter

Rahul Gupta,Sajid Husain,Ankit Kumar,Anders Rydberg,Peter Svedlindh,Rimantas Brucas

doi:10.1002/adom.202001987

Abstract

AbstractTo achieve a large terahertz (THz) amplitude from a spintronic THz emitter (STE), materials with 100% spin polarisation such as Co‐based Heusler compounds as ferromagnetic layer are required. However, these compounds are known to loose their half‐metallicity in the ultrathin film regime, as it is difficult to achieve L21 ordering, which has become a bottleneck for the film growth. Here, the successful deposition using room temperature DC sputtering of the L21 and B2 ordered phases of the Co2FeAl full Heusler compound is reported. Co2FeAl is used as ferromagnetic layer together with highly orientated Pt as nonferromagnetic layer in the Co2FeAl/Pt STE, where an MgO (10 nm) seed layer plays an important role to achieve the L21 and B2 ordering of Co2FeAl. The THz generation in the Co2FeAl/Pt STE is presented, which has a bandwidth of 0.2–4 THz. The THz electric field amplitude is optimized with respect to thickness, orientation, and growth parameters using a thickness dependent model considering the optically induced spin current, superdiffusive spin current, inverse spin Hall effect, and the THz attenuation in the layers. This study, based on the full Heusler Co2FeAl compound opens up a plethora of possibilities in STE research involving full Heusler compounds.

Highlights

Introduction to generate theTHz radiation.[11,12] These magnetic heterostructures are generally referred to as spintronic THz emittersDue to several applications of terahertz (THz) radiation in fun- (STEs)
Rydberg Department of Physics and Astronomy experimentally observed bandwidth depends on the pulse width of the femtosecond laser and the detector used in the terahertz time-domain spectroscopy (THz-TDS) set-up.[12]
On the one hand, when we look at the structure along the MgO [100] substrate direction in cross-sectional transmission electron microscopy (TEM), MgO, and CFA exhibit square lattices corresponding to the MgO(002) and CFA(002) crystal lattice planes when the CFA(002) X-ray diffraction vector is perpendicular to film plane

Summary

Introduction

Introduction to generate theTHz radiation.[11,12] These magnetic heterostructures are generally referred to as spintronic THz emittersDue to several applications of terahertz (THz) radiation in fun- (STEs). To have a large amplitude of the THz-electric field, the thickness of the FM and NFM layers needs to be in the nanometer range.

Results

Conclusion