A 4-fold-symmetry hexagonal ruthenium for magnetic heterostructures   exhibiting enhanced perpendicular magnetic anisotropy and tunnel   magnetoresistance
  An unusual crystallographic orientation of hexagonal Ru with a 4-fold symmetry emerging in epitaxial MgO/Ru/Co2FeAl/MgO heterostructures is reported, in which an approximately Ru(02-23) growth attributes to the lattice matching among MgO, Ru, and Co2FeAl. Perpendicular magnetic anisotropy of the Co2FeAl/MgO interface is substantially enhanced as compared with those with a Cr(001) layer. The MTJs incorporating this structure gave rise to the largest tunnel magnetoresistance for perpendicular MTJs using low damping Heusler alloys. The 4-fold-symmetry hexagonal Ru arises from an epitaxial growth with an unprecedentedly high crystal index, opening a unique pathway for the development of perpendicular anisotropy films of cubic and tetragonal ferromagnetic alloys. 
Zhenchao Wen, Hiroaki Sukegawa, Takao Furubayashi, Jungwoo Koo,   Koichiro Inomata, Seiji Mitani, Jason Paul Hadorn, Tadakat...
cond-mat.mtrl-sci