Ferromagnetism and Anisotropic Spinodal Phase Separation in (In,Fe)As


Ferromagnetism and Anisotropic Spinodal Phase Separation in (In,Fe)As

Yuan, Y.; Hübner, R.; Birowska, M.; Helm, M.; Sawicki, M.; Dietl, T.; Zhou, S.

We report on the experimental observation and theoretical studies of a self-assembled Fe-rich (In,Fe)As nano-lamellar structure that is driven by anisotropic spinodal decomposition at the growth front during laser heating-induced recrystallization of Fe-implanted InAs [1]. Pseudomorphically embedded in the InAs lattice, those Fe-rich nano-lamellae are perpendicular to the (001) surface and parallel to the in-plane [110] crystallographic direction. The Fe atoms are substitutionally incorporated at the indium sites. Magnetic measurements indicate a typical blocked superparamagnetic behavior suggesting strong ferromagnetic orderings inside the Fe-rich nanostructures, but weak coupling between the nano-lamellae. Our findings explain the surprisingly high apparent Curie temperatures and unexpected eight-fold symmetry of crystalline anisotropic magnetoresistance found previously in Be-doped n-type (In,Fe)As grown by molecular beam epitaxy [2]. Prompted by these results we discuss how a different d-level electronic configuration of Fe in InAs and Mn in GaAs [3] affects the magnetic ion incorporation and spatial distribution and, thus, magnetism and anisotropy. Our results also indicate that the directional distribution of impurities or alloy components setting in during the growth may account for the observed nematicity in other classes of correlated systems.

Reference
[1] Y. Yuan, R. Hübner, M. Birowska, C. Xu, M. Wang, S. Prucnal, R. Jakiela, K. Potzger, R. Böttger, S. Facsko, J.A. Majewski, M. Helm, M. Sawicki, S. Zhou, T. Dietl, Nematicity of correlated systems driven by anisotropic chemical phase separation, in Phys. Rev. Materials 2, 114601 (2018).
[2] Pham Nam Hai, D. Sasaki, Le Duc Anh, and M. Tanaka, Crystalline anisotropic magnetoresistance with twofold and eight-fold symmetry in (In,Fe)As ferromagnetic semiconductor, Appl. Phys. Lett. 100, 262409 (2012).
[3] M. Birowska, C. Śliwa, J. A. Majewski, and T. Dietl, Origin of Bulk Uniaxial Anisotropy in Zinc-Blende Dilute Magnetic Semiconductors, Phys. Rev. Lett. 108, 237203 (2012).

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