Great Differences between Low-Temperature Grown Co₂FeSi and Co₂MnSi Films on Single-Crystalline Oxides

Abstract

Using extremely low synthesis temperatures in molecular beam epitaxy (MBE) conditions on MgO(001), SrTiO3(001), and MgAl2O4(001), we find great differences in the crystallinity and magnetic properties between Co-based full-Heusler-alloy Co2FeSi and Co2MnSi films. For example, while L21-ordered Co2FeSi films can be demonstrated on all the oxides even at less than 80 °C, only the B2-ordered and amorphous Co2MnSi films can be obtained. Considering the experimental results and the findings obtained from theoretical calculations, we can conclude that the stability of the Heusler/oxide interfaces and the alloying energy of the disordered Heusler alloys are two of the most important factors for the low-temperature growth of epitaxial Co2FeSi and Co2MnSi films on these oxides. We suggest that Co2FeSi is more suitable for low-temperature formed spintronic devices than Co2MnSi.

Electric field tunable anisotropic magnetoresistance effect in an epitaxial Co2FeSi/BaTiO3 interfacial multiferroic system

“…Co 2 FeSi epilayers were grown on BaTiO 3 (001) substrates by molecular beam epitaxy (MBE) at 200 • C [37][38][39]. Figures 1(a) and 1(b) illustrate the crystal structures and the atomic arrangement of (001) plane for L2 1 -ordered Co 2 FeSi and BaTiO 3 , respectively.…”

“…After loading a BaTiO 3 (001) substrate into an MBE chamber, we performed heat treatment at 400 • C for 20 min with a base pressure of ∼10 −7 Pa. By in situ reflection high-energy electron diffraction (RHEED) observations, good surface flatness of the BaTiO 3 (001) surface was confirmed (not shown here). Cooling the substrate temperature down to 200 • C, we grew Co 2 FeSi layers with thicknesses of 5, 10, and 30 nm by co-evaporating Co, Fe, and Si elements using Knudsen cells [37][38][39]. After the growth, structural characterizations were conducted by in situ RHEED, x-ray diffraction (XRD), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and energy dispersive x-ray spectroscopy (EDX) measurements.…”

Giant magnetoelectric effect in an L21-ordered Co2FeSi/Pb(Mg1/3Nb2/3)O3-PbTiO3 multiferroic heterostructure

“…1(b). Notably, we have shown that the epitaxial and L2 1 -ordered CFS films can be experimentally grown on oxides 37,38 or semiconductor structures. [39][40][41] In this Letter, we experimentally demonstrate an epitaxial and L2 1ordered CFS/PMN-PT(001) multiferroic heterostructure using a molecular beam epitaxy (MBE) technique at 400 C. For the epitaxial Co 2 FeSi/PMN-PT heterostructure, the remanent magnetization state can be largely modulated by varying electric fields.…”

“…After cooling down to the growth temperature of 200 or 400 C, the CFS film was grown by co-evaporating using Knudsen cells, where we set the supplied atomic composition ratio of Co:Fe:Si to 2.0:1.0:1.0 during the growth. 37,39 After the growth, in situ reflection high-energy electron diffraction (RHEED) images are observed, as shown in Figs. 2(a (c) and 2(d), respectively.…”

Co2FeAl Full Heusler Compound Based Spintronic Terahertz Emitter

“…Husain et al [21,22] also reported B2 ordering of CFA deposited on MgO and Si substrates for the relatively larger thickness regime (∼50 nm). Moreover, L2 1 ordering has been achieved for Co 2 FeSi Heusler compounds deposited on MgO, SrTiO 3 , and MgAl 2 O 4 substrates having relatively larger thickness (∼25 nm) [23]. X. Zhang et al reported that the spin polarization varied between 50-60% varying the thickness of B2 ordered CFA films in the range of 5-20 unit cells (∼2.8-12 nm) [24].…”