Tetragonal D0₂₂Mn_3+xGe Epitaxial Films Grown on MgO(100) with a Large Perpendicular Magnetic Anisotropy

Abstract

First-principles calculation of D022 Mn3Ge shows a fully spin-polarized Δ1 band at the Fermi level, low saturation magnetization MS=180 emu/cm3, high uniaxial magnetic anisotropy Ku=23 Merg/cm3, and low Gilbert damping α=9×10-4. We also experimentally investigate D022 Mn3+xGe epitaxial films grown on MgO(100) substrates with different compositions x. The films exhibit a coercivity of about 20 kOe, MS of about 130 emu/cm3, and Ku of about 10 Merg/cm3 at x=0.55 (78 at.% Mn). These indicate that D022 Mn3Ge is a good candidate for spin-transfer-torque random access memory.

Epitaxial Growth of Hard Ferrimagnetic Mn3Ge Film on Rhodium Buffer Layer

“…One possibility is the difference between the optimal composition of the Mn-Ge layer on the Cr and Cr/Rh layers. Mn-Ge has different optimal compositions for obtaining D0 22 structure and the best magnetic properties, e.g., Mn 3.4 Ge in the bulk state [33], Mn 3.55 Ge in the thin film state on MgO (001) [28], and Mn 3 Ge in the thin film state on Cr (001) [22,27]. It may be necessary to optimize the composition of the Mn 3 Ge layer to obtain the best magnetic properties on a Cr/Rh buffer layer.…”

“…Films with stoichiometric compositions exhibited a K u value of 11.8 Merg/cm 3 and an M s value of ∼110 emu/cm Figure 1e) [22]. D0 22 Mn 3 Ge is considered to have the properties most suitable for MRAM [28,29], although few examples of epitaxial growth have been reported. In particular, it is unclear how lattice matching between Mn 3 Ge and the buffer or substrate affect the magnetic properties of films.…”

High perpendicular magnetic anisotropy in D22-Mn3+xGe tetragonal Heusler alloy films

“…On the other hand, the D0 22 -structured Mn 3þx Ge tetragonal Heusler alloy has been predicted to possess a low a (9 Â 10 À4 ), 21 high K u (>22.9 Merg/cm 3 ), 21,22 and high P (77%), 23 as well as half-metallic band dispersion (P ¼ 100%) in the (001) crystallographic direction, 21,23 which could lead to an extremely high TMR. 23 These theoretical results imply that D0 22 -Mn 3þx Ge is another promising candidate material for STT-MRAM electrodes.…”

“…22 On the other hand, the D0 22 -Mn 3.55 Ge films grown on MgO was reported, which also showed high K u of about 10 Merg/cm 3 with a large experimental error (K u ¼ 10 6 3 Merg/cm 3 ). 21 For high density STT-MRAM application, it is very important issue to clarify whether experimental K u value for D0 22 -Mn 3þx Ge is clearly over 10 Merg/cm 3 . However, it is not yet clear whether K u for D0 22 -Mn 3þx Ge is higher than 10 Merg/cm 3 or not.…”

Isotropic, high coercive field in melt-spun tetragonal Heusler Mn3Ge

“…High coercivity in epitaxial thin films is usually attributed to the preferential tetragonal c-axis orientation along the film normal, 11 leading to perpendicular magnetic anisotropy. Magnetocrystalline anisotropy of 1.1 MJm −312,13 and coercivity up to µ 0 H C = 3.5 T, 14 and more a Electronic mail: kalache@cpfs.mpg.de b Electronic mail: felser@cpfs.mpg.de recently over 6 T on appropriate buffer layers, 15 have been reported. Here we focus on structural, microstructural, and magnetic properties of bulk melt-spun D0 22 Mn 3 Ge ribbons.…”