PERPENDICULAR MAGNETIC ANISOTROPY IN HUESLER Co₂MnSi FOR SPINTRONIC DEVICES

Spin-electronics exploits the electron spin as an additional degree of freedom in solid-state devices, thus achieving additional functionalities. Amongst these are novel opto-electronic devices in which injection of perpendicularly polarized electrons from a ferromagnetic electrode into a light-emitting-diode yields circularly polarized photons[1]. Butler et al.[2] predict that such electron injection with high polarization is achieved with an ultrathin (2-3nm) chemically-ordered Co₂MnSi (CMS) full Heusler due to both perpendicular magnetic anisotropy (PMA) and half-metallicity. PMA is expected due to tetragonal distortion of cubic CMS on epitaxial MgO(001).

Here, we correlate between structure and magnetic properties of magnetron sputter-deposited CMS electrodes with varying thicknesses, interfaces, and annealing temperatures using transmission electron microscopy (TEM: phase contrast, energy-loss spectroscopy, Z-contrast scanning TEM) and magnetometry.

We indeed observe PMA in ultra-thin CMS though structural characterization indicates chemical intermixing of the Heusler layer with both the MgO and Pd adjacent layers. Furthermore, the CMS ultra-thin layers have a low degree of crystallinity and saturation moment as opposed to thicker layers (tens of nm) which are typically used for structural characterization[3]. Consequently, PMA is attributed mostly to interface intermixing comparable to Co/Pd multilayers[4].

• Farshchi et al. "Optical communication of spin information between light emitting diodes" Applied Physics Letters98.16(2011).
• Munira, et al. "Achieving perpendicular anisotropy in half-metallic Heusler alloys for spin device applications" Journal of Applied Physics115.17(2014).
• Tal, A. Kohn et al. "The role of structure on magneto-transport properties of Heusler Co2MnSi films deposited on MgO (001)" Journal of Applied Physics 114.16(2013).
• J.A. Den Broeder et al. "Magnetic properties and structure of Pd/Co and Pd/Fe multilayers" Journal of Applied Physics 61.8(1987).