The antiphase boundary in half-metallic Heusler alloy Co2Fe(Al,Si): atomic structure, spin polarization reversal, and domain wall effects

Abstract

Atomic resolution scanning transmission electron microscopy reveals the presence of an antiphase boundary in the half-metallic Co 2 Fe(Al,Si) full Heusler alloy. By employing the density functional theory calculations, we show that this defect leads to reversal of the sign of the spin-polarization in the vicinity of the defect. In addition, we show that this defect reduces the strength of the exchange interactions, without changing the ferromagnetic ordering across the boundary. Atomistic spin calculations predict that this effect reduces the width of the magnetic domain wall compared to that in the bulk. Published by AIP Publishing. [http://dx

Role of anti-phase boundaries in the formation of magnetic domains in magnetite thin films

“…Anti-phase boundaries (APBs) are extended defects appearing in crystalline materials, created by a fractional displacement of the lattice constant between atomic planes. They have been observed in many materials such as Co 2 Fe(Al, Si) Heusler alloy [1], MnAl [2], GaAs [3] and magnetite (Fe 3 O 4 ) [ 4], as well as in different types of nanostructures, e.g. thin films [4][5][6] or nanoparticles [7].…”

Effect of annealing on the structure and magnetic properties of Co2FeAl0.5Si0.5 thin films on Ge(111)

“…Despite the predicted ideal properties of fully ordered L2 1 single crystal half-metallic Heusler alloys, structural defects and chemical disorder can drastically change the spin polarisation [7,15,16] in Heusler thin films. In order to improve spin-electronic properties, thermal treatment is essential not only to remove the point-and extended structural defects but also to achieve the chemically-ordered L2 1 phase throughout the film [17,18].…”

“…In contrast to CFAS/Si where extensive intermixing has been observed even for room temperature deposition [5], recent studies of CFAS films on Ge(111) have demonstrated atomically and chemically sharp interfaces for room temperature deposition [6]. The structural phase of the room temperature deposited CFAS is B2 and defects such as antiphase boundaries, which locally destroy the spin polarisation, have been observed [7]. Therefore, it is important to determine how the annealing affects overall film structure as well as the atomic and chemical structure of the CFAS/Ge interface.…”

“…Efficient spin-injection from half-metallic ferromagnets into semiconductors is crucial for the development of hybrid spintronic devices such as spin transistors [1][2][3][4]. Half-metallic ferromagnets such as Co-based full Heusler alloys that are 100% spin-polarized at the Fermi-level are ideal candidates for such devices [5][6][7][8]. In particular, Co 2 FeSi 0.5 Al 0.5 (CFAS) shows great promise due to its high Curie temperature, high magnetic moment, mid-gap Fermi level, and low Gilbert damping constant [9][10][11][12][13][14].…”

A modulated structure derived from the XA-type Mn2RuSn Heusler compound

“…Antiphase boundary (APB), as one of the important microor nanostructures, was investigated in the Heusler compounds to explore its effects on magnetic properties, e.g. domains, spin-polarization and exchange interactions (Lapworth et al, 1971;Venkateswaran et al, 2007;Umetsu et al, 2011;Murakami et al, 2013;Nedelkoski et al, 2016;Niitsu et al, 2017;Vronka et al, 2020;Levin et al, 2021). Intensive studies on the APB and its related long-periodic structures were initially investigated in AuCu, AuCu 3 and Au 3 Cu (Ogawa & Watanabe, 1954;Glossop & Pashley, 1959;Yamaguchi et al, 1962;Toth & Sato, 1964;Hashimoto & Ogawa, 1970;Sinclair & Thomas, 1975).…”