Engineered Heusler Ferrimagnets with a Large Perpendicular Magnetic Anisotropy

Area of Science:

• Materials Science
• Condensed Matter Physics
• Spintronics

Background:

• Perpendicular magnetic anisotropy (PMA) is essential for high-density magnetic storage devices.
• Heusler alloys offer tunable magnetic properties for advanced spintronic applications.
• Interfacial coupling in thin-film heterostructures significantly influences magnetic behavior.

Purpose of the Study:

• To investigate the growth and magnetic properties of Co₂MnSi/MnGa bilayers with varying Co₂MnSi thicknesses.
• To explore the effect of post-annealing on the structural and magnetic characteristics of these bilayers.
• To determine the critical thickness for observing PMA with antiferromagnetic (AFM) coupling in Co₂MnSi/MnGa systems.

Main Methods:

• Epitaxial growth of D0₂₂-MnGa and Co₂MnSi (CMS) films on MgO substrates using sputtering.
• Fabrication of two sample series: as-grown and post-annealed at 400 °C.
• Structural characterization using X-ray diffraction (XRD) to confirm film structure and epitaxy.
• Magnetic property measurements to determine remnant magnetization and switching fields.

Main Results:

• Successful epitaxial growth of MnGa and CMS films, with the cubic L2₁ structure of CMS observed down to 3 nm thickness.
• Evidence of antiferromagnetic (AFM) interfacial exchange coupling (Jex) between MnGa and CMS films in bilayers, indicated by reduced remnant magnetization and increased switching fields.
• Determination of a critical CMS thickness below 10 nm for observing PMA with AFM coupling, which is larger than in previous studies.

Conclusions:

• Co₂MnSi/MnGa bilayers exhibit synthetic PMA with significant AFM interfacial coupling.
• The observed critical thickness suggests potential for novel spintronic device designs.
• Post-annealing does not fundamentally alter the observed PMA and AFM coupling behavior in these specific structures.