Доклад проф. А. Фуджимори "Origins of magnetic anisotropy of 2D materials studied by x-ray magnetic circular dichroism"

19 августа 2021 года

Уважаемые коллеги!

В четверг, 26 августа в 15:00 состоится доклад проф. А. Фуджимори (Токийский университет, Япония) на тему: Origins of magnetic anisotropy of 2D materials studied by x-ray magnetic circular dichroism.

Доклад будет проходить в очно/заочной форме в малом зале и с помощью сервиса zoom (ссылка будет выслана позднее).

После доклада будет иметься возможность пообщаться с проф. Фуджимори.
 

ABSTRACT:
In order to realize ferromagnetism in 2D materials, perpendicular magnetic anisotropy (MA) is necessary because, according to the Wigner-Mermin theorem, magnetic order cannot not occur in the isotropic 2D Heisenberg model. We have studied the origins of perpendicular MA in 2D ferromagnets using x-ray magnetic circular dichroism (XMCD) combined with cluster-model calculation.

(1)  In “t2g systems”, where the t2g level of the transition-metal ion is partially filled, the single-ion anisotropy (SIA) arising from spin-orbit coupling (SOC) and low-symmetry crystal field leads to MA and hence ferromagnetic order. XMCD results on (Ba,K)(Zn,Mn)2As2, a 2D version of Ga1-xMnxAs [1], and FexTiS2 [2] will be presented.

(2)  In half-filled systems, where the distribution of transition-metal 3d electrons is highly symmetric, the SIA is small. The Cr3+ ion in the van der Waals ferromagnet Cr2Ge2Te6 is shown to have negligibly small SIA [3], consistent with the scenario that anisotropic exchange mediated by ligand p orbitals with strong SOC is responsible for the MA.

(3)  In “eg systems”, the partially-filled eg electrons do not carry orbital magnetic moment and hence the SIA is small. On the other hand, the anisotropic distribution of eg electrons (so-called magnetic dipole) contributes to MA, as demonstrated by an XMCD study of strained La1-xSrxMnO3 film [4]. Magnetic dipole plays a dominant role also in the perpendicular MA of the layered L10-type FePt alloy [5].

[1] S. Sakamoto et al., ACS Appl. Electron. Mater. 3 (2021).
[2] G. Shibata et al., J. Phys. Chem. C 125, 12929 (2021).
[3] M. Suzuki et al., submitted to Phys. Rev. Mater.
[4] G. Shibata et al., npj Quantum Mater. 3, 3 (2018).
[5] K. Ikeda et al., Appl. Phys. Lett. 111, 142402 (2017).