Observation of spontaneous spin-splitting in the band structure of an n-type zinc-blende ferromagnetic semiconductor

Abstract

Large spin splitting in the conduction band (CB) and valence band (VB) of ferromagnetic semiconductors (FMSs), predicted by the influential mean-field Zener model[1,2] and assumed in many spintronic device proposals[3-8], has never been observed in the mainstream p-type Mn-doped FMSs[9-15]. Here using tunnelling spectroscopy in Esaki-diode structures, we report the observation of such a large spontaneous spin-splitting energy (ΔE = 31.7 - 50 meV) in the CB bottom of n-type FMS (In,Fe)As, which is surprising considering the very weak s-d exchange interaction reported in several zinc-blende (ZB) type semiconductors[16,17]. The mean-field Zener model also fails to explain consistently the ferromagnetism and the spin splitting energy ΔE of (In,Fe)As, because we found that the Curie temperature (TC) values calculated using the observed ΔE are much lower than the experimental TC by a factor of 400. These results urge the need for a more sophisticated theory of FMSs. Furthermore, bias-dependent tunnelling anisotropic magnetoresistance (TAMR) reveals the magnetic anisotropy of each component of the (In,Fe)As band structure [CB, VB, and impurity band (IB)]. The results suggest that the energy range of IB overlaps with the CB bottom or VB top, which may be important to understand the strong s-d exchange interaction in (In,Fe)As[18,19].

arXiv commentmain manuscript: page 1-22, supplementary materials: page 23-36

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• Spin triplet superconducting proximity effect in a ferromagnetic semiconductor
• Minority-Spin Impurity Band in n-Type (In,Fe)As: A Materials Perspective for Ferromagnetic Semiconductors
• Densities of states in Fe-doped III-V semiconductors: a first-principles study
• Magnetization process of the insulating ferromagnetic semiconductor (Al,Fe)Sb
• Ferromagnetism and giant magnetoresistance in zinc-blende FeAs monolayers embedded in semiconductor structures
• Growth and characterization of quaternary-alloy ferromagnetic semiconductor (In,Ga,Fe)Sb
• Spin gapped metals: A novel class of materials for multifunctional spintronic devices
• Chern insulator in a ferromagnetic two-dimensional electron system with Dresselhaus spin-orbit coupling
• Current-in-plane spin-valve magnetoresistance in ferromagnetic semiconductor (Ga,Fe)Sb heterostructures with high Curie temperature