Anomlous Hall Effect in Single Crystal Heusler Alloy Co₂MnAl

Discoveries of Weyl semimetals have attracted much attention due to their unique properties. Weyl semimetal states in ferromagnetic (FM) materials are expected to be particularly useful for spintronic applications. However, despite numerous efforts, FM Weyl semimetals are still missing. Co-based Heusler alloys with the formula of Co₂XZ (X = IVB or VB; Z = IVA or IIIA) were recently predicted to be FM Weyl semimetals [1]. But there has been no reported experimental evidence up to date, partly because single crystal growth of these materials is challenging. In this presentation, we will show our recent studies on Co₂MnAl single crystals grown by floating zone methods. Our magnetic measurements verifies both its room temperature ferromagnetism and its magnetic anisotropy. Moreover, our magnetotransport measurements unveils a remarkable anomalous Hall effect with exceptionally high Hall conductivity [~1800 (W cm)^-1 at 2K], consistent with the theoretical prediction that large anomalous Hall conductivity of Co₂MnAl caused by non-trivial band topology [2].
Key words: Heusler alloy, single crystal, Anomlous Hall effect
[1] Z.J. Wang et al., Phys. Rev. Lett. 117, 236401(2016)
[2] J. Kubler and C. Felser, Phys. Rev. B 85, 012405 (2012)