Transfer-matrix description of heterostructured spintronics terahertz emitters

Yang, Yingshu; Forno, Stefano Dal; Battiato, Marco

doi:10.1103/physrevb.104.155437

Cited by 11 publications

(12 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We can clearly see that to account for the small changes in the ratio, a rather long spin-current attenuation length on the order of 50 nm needs to be assumed. As predicted by Yang et al [29], we believe that most estimations in the literature might underestimate the spin-current attenuation length if they do not properly account for the largely dominant contribution to the signal attenuation from the THz optics. In the following we will attempt to give a more intuitive understanding of the complexity of the problem and will develop a model to account for the sharp drop in THz signal.…”

mentioning

confidence: 70%

“…In order to gain more insights into the emission process, we developed a model [35] based on the transfer-matrix approach in which we consider a THz current source [29,36,37] located at the interface of the Pt layer nearest to the Co. To this aim we assume an infinitely thin slab of current oscillating at THz frequencies which creates a discontinuity in the tangential H field within the stack. We then calculate the total electromagnetic field inside and outside the film (E TTM ) by setting the incident waves to zero.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Is terahertz emission a good probe of the spin current attenuation length?

Gorchon

Mangin

Hehn

et al. 2022

Applied Physics Letters

View full text Add to dashboard Cite

Terahertz (THz) emission from magnetic films has recently become an important characterization tool of spintronic properties, particularly since no patterning is required. One such property of interest is the spin-current attenuation length. When separating a magnetic film from a spin-to-charge converter with a light metal, the emitted intensity reduces almost exponentially with the thickness of the spacer. However, the extracted characteristic length is more than an order of magnitude smaller than the spin diffusion length measured in equilibrium. In this work, we experimentally and theoretically demonstrate that most of the observed decay in the THz emission is of optical (THz) origin. We are able to estimate a spin current attenuation length for Cu of ∼50 nm in much closer agreement with spin diffusion length measurements. We conclude that THz emission remains a powerful characterization technique, but due to the high number of intricate conversion mechanisms, and most importantly, due to the high sensitivity to changes in the optical properties, extracting absolute numbers for spintronic phenomena remains extremely challenging.

show abstract

mentioning

confidence: 70%

mentioning

confidence: 99%

Is terahertz emission a good probe of the spin current attenuation length?

Gorchon

Mangin

Hehn

et al. 2022

Applied Physics Letters

View full text Add to dashboard Cite

show abstract

“…Employing this to reconstruct the electric field in the time domain requires an additional phase information between the frequency components within the terahertz bandwidth. Therefore, in this work, we utilize a Transfer Matrix Method (TMM) 22 with modifications 23 that provides an additional factor to describe the phase separation between the THz frequency components. Remarkably, the results reveal a linear relationship between the terahertz pulse amplitude and the charge current amplitude.…”

Section: Introductionmentioning

confidence: 99%

“…Phenomenologically, the proposed THz-H hysteresis requires to exhibit THz pulse amplitude, 𝑬 (𝑡) 𝒑𝒆𝒂𝒌 ∝ charge current amplitude (𝒋 𝒄 𝒑𝒆𝒂𝒌 ) or ∝ spin current amplitude (𝒋 𝒔 𝒑𝒆𝒂𝒌 ) . To describe the relation between the charge current and THz emission, we utilize a modified transfer matrix method (TMM) 23 that model the propagation of THz wave in the heterostructures which self-accounts for multiple reflections across the thickness of the sample (refer to Section S4 in Supplementary Information for theoretical details). Previously applied theoretical techniques have relied on several approximations 4,25 .…”

Section: Introductionmentioning

confidence: 99%

“…Here we go beyond previous approximations using a modified TMM 23 Besides the bilayer heterostructure, which generates a unidirectional spin transport, we also measure the THz-H hysteresis for more complex heterostructures with a bidirectional spin transport 15 . Such structures produce coupled charge currents on either side of the ferromagnet while experiencing ISHE from the adjacent placed layers, as shown in figure 3(a).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Terahertz spintronic magnetometer (TSM)

Agarwal

Yang

Lourembam

et al. 2022

Applied Physics Letters

Self Cite

View full text Add to dashboard Cite

A ferromagnetic metal consists of localized electrons and conduction electrons coupled through strong exchange interaction. Together, these localized electrons contribute to the magnetization of the system, while conduction electrons lead to the formation of spin and charge current. Femtosecond out of equilibrium photoexcitation of ferromagnetic thin films generates a transient spin current at ultrafast timescales that have opened a route to probe magnetism offered by the conduction electrons. In the presence of a neighboring heavy metal layer, the non-equilibrium spin current is converted into a pulsed charge current and gives rise to terahertz (THz) emission. Here, we propose and demonstrate a tool known as the terahertz spintronic magnetometry. The hysteresis loop obtained by sweeping terahertz (THz) pulse amplitude as a function of the magnetic field is in excellent agreement with the vibrating-sample magnetometer measurements. Furthermore, a modified transfer-matrix method employed to model the THz propagation within the heterostructure theoretically elucidates a linear relationship between the THz pulse amplitude and sample magnetization. The strong correlation, thus, reveals spintronic terahertz emission as an ultrafast magnetometry tool with reliable in-plane magnetization detection, highlighting its technological importance in the characterization of ferromagnetic thin-films through terahertz spintronic emission spectroscopy.

show abstract

Secondary Spin Current Driven Efficient THz Spintronic Emitters

Agarwal,

Yang,

Medwal

et al. 2023

Advanced Optical Materials

Self Cite

View full text Add to dashboard Cite

Femtosecond laser‐induced photoexcitation of ferromagnet (FM)/heavy metal (HM) heterostructures has attracted attention by emitting broadband terahertz frequencies. The phenomenon relies on the formation of an ultrafast spin current, which is primarily attributed to the direct photoexcitation of the FM layer. However, during the process, the FM layer also experiences a secondary excitation led by the hot electrons from the HM layer that travel across the FM/HM interface and transfer additional energy in the FM. Thus, the generated secondary spins enhance the total spin current formation and lead to amplified spintronic terahertz emission. These results emphasize the significance of the secondary spin current, which even exceeds the primary spin currents when FM/HM heterostructures with thicker HM are used. An analytical model is developed to provide deeper insights into the microscopic processes within the individual layers, underlining the generalized ultrafast superdiffusive spin‐transport mechanism.

show abstract

Transfer-matrix description of heterostructured spintronics terahertz emitters

Cited by 11 publications

References 32 publications

Is terahertz emission a good probe of the spin current attenuation length?

Is terahertz emission a good probe of the spin current attenuation length?

Terahertz spintronic magnetometer (TSM)

Secondary Spin Current Driven Efficient THz Spintronic Emitters

Contact Info

Product

Resources

About