Half-metallic Antiferromagnet Sheets in Sr4M2O6CrFeAs2 (M=Sc, Cr) and Their Bulk Form

TL;DR

This study uses first-principles calculations to demonstrate that Sr4M2O6CrFeAs2 layers exhibit robust half-metallic antiferromagnetism, and a magnetic field can align spins to restore bulk HMAFM properties.

Contribution

It reveals the existence of half-metallic antiferromagnetic layers in Sr4M2O6CrFeAs2 and proposes a method to restore bulk HMAFM by magnetic field alignment.

Findings

CrFeAs2 layers are half-metallic antiferromagnetic.

Interlayer coupling is negligible due to thick blocking layers.

Magnetic field can align spins to restore bulk HMAFM.

Abstract

We reveal by first-principles calculations that in iron pnictides Sr4M2O6CrFeAs2 (M=Sc, Cr) the two-dimensional CrFeAs2 layers exhibit a robust band structure of half-metallic antiferromagnet (HMAFM). Due to the thick blocking layer, the interlayer coupling is vanishingly small and thus the conductive channels in individual layers may take the alternative spin direction randomly. We show that, since the spin magnetizations of Fe and Cr are different in a ferromagnetic state, applying a strong magnetic field and ramping it down gradually can align the spin direction of conductive channel of all HMAFM layers, which restores the bulk HMAFM.