Structural and magnetic properties of cubic and tetragonal Heusler alloy bilayers

Abstract

Different cubic Co-based Heusler alloys-Co 2 FeAl (CFA), Co 2 FeSi (CFS), Co 2 MnAl (CMA), and Co 2 MnSi (CMS)-were grown epitaxially on tetragonal Heusler-like D0 22-MnGa at different annealing temperatures (T a) in the form of Heusler (20 nm)/MnGa (30 nm) bilayers. The CMA/MnGa bilayer showed the largest critical temperature (450 • C), indicating good structural stability against interdiffusion. The experimental results showed an easier interdiffusion of the Fe and Si elements than of Mn and Al. An inverted hysteresis loop was observed in a polar magneto-optical Kerr effect (P-MOKE) measurement for the CFS/MnGa, CMA/MnGa, and CMS/MnGa bilayers. This is one piece of evidence for the existence of the antiferromagnetic (AFM) interfacial exchange coupling (J ex). We evaluated J ex for the Heusler/MnGa bilayers annealed at different temperatures. J ex changed from ferromagnetic (FM) to AFM after annealing at 300 • C for the CFA/MnGa bilayer. Other bilayers showed only AFM coupling. The strongest J ex value of approximately-3.2 erg/cm 2 was obtained for the CMS/MnGa bilayer annealed at 400 • C. It was found that the tendency of the Mn and Si elements to make AFM J ex in the Heusler/MnGa bilayers interfaces is larger than that of Fe and Al.

Structural, electronic and magnetic properties of MnxGa/Co2MnSi (x = 1, 3) bilayers

“…In AFM MM-MS_B interface with the lowest formation energy, the optimized in-plane lattice constants are 3.785 Å and 3.846 Å for D0 22 -MG/CMS and L1 0 -MG/CMS bilayers, respectively, while the optimized lattice constant of CMS bulk is 5.627 Å. Thus, the estimated lattice mismatch value of the MM-MS_B interface are 2.64% in the D0 22 -MG/CMS bilayer and 1.17% in the L1 0 -MG/CMS bilayer, indicating that the lattice of the CMS is contracted to fit the MG lattice at the bottom of the MG/CMS, as has observed experimentally 24 – 26 . The following discussion will only focus on the magnetic and electronic properties of the AFM MM-MS_B interface in both D0 22 -MG/CMS and L1 0 -MG/CMS bilayers due to their lowest energies in both PBE and PBEsol functionals.…”

“…As a soft magnetic alloy, the Co 2 MnSi is expected to be applied in hybridized electrode as interlayer because the MnGa alloys have a structure derived from Heusler alloys. The exchange coupling between Co-based Heusler alloys and D0 22 -MnGa films has been investigated experimentally 24 – 26 . Among several kinds of Co-based Heusler compounds, Co 2 MnSi was indeed identified to show the highest interfacial AFM coupling strength with D0 22 -MnGa.…”

MnGa-based fully perpendicular magnetic tunnel junctions with ultrathin Co2MnSi interlayers

“…The AFM exchange coupling between Co-based Heusler alloys and MnGa films has been investigated previously by Ranjbar et al . 18 Among several kinds of Co-based Heusler compounds, Co 2 MnSi was identified to show the highest interfacial AFM coupling strength ( J ex ) with MnGa 19 .…”

Perpendicularly Magnetized MnxGa‐Based Magnetic Tunnel Junctions: Materials, Mechanisms, Performances, and Potential Applications

“…Later, Ranjbar et al systematically investigated the structural and magnetic properties of the bilayer systems composed of D0 22 -Mn 3 Ga and typical cubic Co-based Heusler alloys, including Co 2 FeAl (CFA), Co 2 FeSi (CFS), Co 2 MnAl (CMA), and Co 2 MnSi (CMS). [94] These bilayer films were epitaxially grown on (001) MgO single-crystalline substrates with different annealing temperatures T a . Figure 5a-d shows the out-of-plane and inplane M-H loops for the as-grown MnGa/CFA, MnGa/CFS, MnGa/CMA, and MnGa/CMS bilayers, respectively.…”