Metallic superlattices such as Co/Ir/Co exhibit the symmetric interlayer exchange coupling (IEC) (1). Recently, the antisymmetric interlayer exchange coupling (AIEC) was observed in a metallic superlattice when the in-plane spatial inversion symmetry was broken (2-5). However, the controllability and the applicability of AIEC have not been examined yet, and the systematic experiments exploiting well-controlled in-plane structural asymmetry are indispensable. This study systematically investigated the AIEC for the wedge-shaped Pt/Co/Ir/Co/Pt to clarify the nature of AIEC.
A double-wedged sample (DWS) of Ta (1)/Pt (2)/Co (tCo)/Ir (tIr)/Co (0.5)/Pt (2)/Ta (1) (thickness in nm) was deposited on a SiOx substrate using magnetron sputtering. The tCo and tIr were continuously varied from 0.6 to 1.6 nm and from 0 to 1.5 nm, respectively. The wedge direction of the Ir layer was orthogonal to that of the wedged bottom Co layer. DWS was patterned into Hall-bar-shaped devices, and the magnetic properties were investigated by exploiting the anomalous Hall effect (AHE). The IEC in Co/Ir/Co was confirmed from the periodic change of the saturation field (μ0Hs) against tIr. The AHE curves were largely shifted with an additional in-plane magnetic field (μ0Hip) of 50 mT (Fig. 1), indicating the existence of AIEC. The largest switching field shift (μ0ΔHsw) was 14.8 mT at tCo ~ 0.80 nm and tIr ~ 0.27 nm, which was an order of magnitude larger than the values reported previously (0.7~1.7 mT (3,5)). Similar to the tIr dependence of μ0Hs, μ0ΔHsw showed the oscillatory change against tIr with a local minimum at tIr ~ 0.87 nm, suggesting the correlation between the symmetric IEC and the AIEC. Furthermore, we developed the extended Stoner-Wohlfarth model and proposed the tunability of the AIEC effective field by the ratio of the AIEC energy and the antiferromagnetic coupling strength. Finally, we theoretically and experimentally demonstrated the perpendicular magnetization switching solely induced by μ0Hip for DWS. This study provides crucial information to manipulate the three-dimensional chiral magnetic structures (6). 

**References:** 
[1] M. D. Stiles, J. Magn. Magn. Mater., Vol. 200, p.322-337 (1999). 
[2] E. Y. Vedmedenko et al., Phys. Rev. Lett., Vol. 122, p.257202 (2019). 
[3] D.-S. Han et al., Nat. Mater., Vol. 18, p.703 (2019). 
[4] A. Fernández-Pacheco et al., Nat. Mater., Vol. 18, p.679 (2019). 
[5] K. Wang et al., Commun., Phys. Vol. 4, p.10 (2021). 
[6] H. Masuda et al., Phys. Rev. Appl., Vol. 17, p.054036 (2022). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/75f4d3788c7d291090132b997eb8f2cd.png)

Large antisymmetric interlayer exchange coupling enabling perpendicular magnetization switching by an in plane magnetic field

The thermoelectric generation based on the anomalous Nernst effect (ANE) has become one of the promising approaches to realize efficient energy harvesting from waste heat and heat flux sensor due to its several advantages over conventional devices based on the Seebeck effect (SE) 1,2. However, till date, the observed ANE thermopower is very small and a systematic material investigation to realize large anomalous Nernst coefficient is necessary. Recent theoretical and experimental investigations identified a Weyl semimetal as a potential material having giant ANE which can be achieved by a little tuning of Fermi level (EF) near Weyl points3,4,5. However, systematic tuning of EF and investigation of thermoelectric properties based on many films with different compositions are time-consuming. Furthermore, in this process, one losses many intermediate compositions due to the limitation of number of films that can be prepared. In this regard, we introduce an efficient approach to tune EF for Weyl semimetals and demonstrate the approach through a layer-by-layer combinatorial deposition of a Co2MnAl1-xSix (CMAS) thin film with x varied from 0 to 1 on a single substrate. The fabrication procedure is represented schematically in Fig.1 (a). The structural characterization reveals the formation of single-phase CMAS alloys throughout the composition range. Hard X-ray photoemission spectroscopy (HAXPES) directly confirmed a continuous shifting of EF from Co2MnAl to Co2MnSi with a maximum shift of 0.4 eV (see Fig.1. (b)), which is consistent with the theoretical prediction. We also measured the anomalous Ettingshausen effect (AEE), the reciprocal of ANE, for the all x range using a single strip along the composition gradient (see Fig.1. (c)) by means of the lock-in thermography technique6,7. Only one LIT image tells us that large AEE is obtained between x = 0.06 to 0.12, which well agrees with the composition dependence of the ANE signals (see Fig.1. (d)), measured by making many parallelly aligned Hall bars elongated to the orthogonal direction to the composition gradient (see Fig.1. (c)). The findings clearly demonstrate that the AEE measurement using the composition spread film is an effective approach to investigate the composition dependence of ANE and find the highest performance without fabricating many films and performing systematic measurements. These demonstrations will enable the optimization of the composition in Weyl semimetals and exploration of new materials to obtain giant ANE/AEE, which is essential to realize applications based on the transverse thermoelectric effects.

**References:**

[1] Y. Sakuraba et al., Appl. Phys. Express 6, 033003 (2013) [2] W. Zhou et al., Appl. Phys. Express 13, 043001 (2020) [3] K. Sumida et al., Commun. Mater. 1, 89 (2020) [4] J. Noky et al., NPJ Comput. Mater. 6, 77 (2020) [5] Y. Sakuraba et al., Phys. Rev. B 101, 134407 (2020) [6] S. Daimon et al., Nat. Commun. 7, 13754 (2016) [7] T. Seki et al., Appl. Phys. Lett. 112, 152403 (2018)

**Images:**

![](https://assets.underline.io/uploads/markdown_image/1/image/58d6615be315220821aa1a7a138fb225.jpg)
Fig.1 (a) Schematic representation of composition-spread CMAS combinatorial film deposited with wedge shaped layer by layer deposition (b) Valance band HAXPES spectra for CMAS composition-spread film at Co2MnAl (CMA) and Co2MnSi (CMS) side (c) Schematic measurement configuration used for ANE and AEE (d) AAEE/jc and SANE as a function of x. Where AAEE is the amplitude of temperature modulation due to AEE, jc is the charge current density and SANE is anomalous Nernst coefficient. The inset shows observed AAEE image in LIT.

 Efficient tuning of electronic, transport, and thermoelectric properties of Weyl semimetal Co2MnAl1-xSix composition-spread thin film

EOB: Antiferromagnetic Spintronics II

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Large antisymmetric interlayer exchange coupling enabling perpendicular magnetization switching by an in plane magnetic field

Efficient tuning of electronic, transport, and thermoelectric properties of Weyl semimetal Co2MnAl1-xSix composition-spread thin film

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