Frequency‐Independent Terahertz Anomalous Hall Effect in DyCo₅, Co₃₂Fe₆₈, and Gd₂₇Fe₇₃ Thin Films from DC to 40 THz

Abstract

The anomalous Hall effect (AHE) is a fundamental spintronic charge‐to‐charge‐current conversion phenomenon and closely related to spin‐to‐charge‐current conversion by the spin Hall effect. Future high‐speed spintronic devices will crucially rely on such conversion phenomena at terahertz (THz) frequencies. Here, it is revealed that the AHE remains operative from DC up to 40 THz with a flat frequency response in thin films of three technologically relevant magnetic materials: DyCo5, Co32Fe68, and Gd27Fe73. The frequency‐dependent conductivity‐tensor elements σxx and σyx are measured, and good agreement with DC measurements is found. The experimental findings are fully consistent with ab initio calculations of σyx for CoFe and highlight the role of the large Drude scattering rate (≈100 THz) of metal thin films, which smears out any sharp spectral features of the THz AHE. Finally, it is found that the intrinsic contribution to the THz AHE dominates over the extrinsic mechanisms for the Co32Fe68 sample. The results imply that the AHE and related effects such as the spin Hall effect are highly promising ingredients of future THz spintronic devices reliably operating from DC to 40 THz and beyond.

Impact of gigahertz and terahertz transport regimes on spin propagation and conversion in the antiferromagnet IrMn

“…The good agreement of GHz and THz S2C efficiency in both thickness limits is consistent with previous studies that compared THz and low-frequency regimes of spin-orbit-couplingbased effects. 32,46,47 As y 0 ( y 1 in most cases, the IrMn layer behaves like a simple spin-current attenuator, and we can justify the mono-exponential approximation in Eq. ( 2).…”

Terahertz spintronic magnetometer (TSM)

“…This charge current, 𝒋 𝒄 is given by 𝒋 𝒄 = 𝛾𝒋 𝒔 × 𝑴/|𝑴| 15 where 𝑴/|𝑴| denotes the magnetization unit vector of the FM layer and 𝛾 signifies the spin Hall angle of the HM layer. Recent studies have highlighted the potential of the linear relation between the 𝒋 𝒄 and 𝒋 𝒔 where the measure of 𝒋 𝒄 relates to the spin ordering in the system [17][18][19] . Empirically, the terahertz pulse amplitude follows the magnetization behavior of the FM 20,21 , however, the underlying microscopic processes are largely unexplored and require a rigorous investigation to establish the physical interpretations of the terahertz pulse amplitude.…”

Direct evidence of terahertz emission arising from anomalous Hall effect

“…The conduction electrons involved in the super-diffusive transport model are located close to the Fermi level, making them equivalent to the conduction electrons in the diffusive transport model. Seifert et al 29 demonstrated that the anomalous Hall conductivity and anomalous Hall angle are frequency-independent up to 40 THz, and therefore consistent with the DC anomalous Hall conductivity within an error bar of 2%.

Figure 5 ( a ) Transmission ( T ), reflectance ( R ) and absorption ( A ) vs. .

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