Influence of boron diffusion on the perpendicular magnetic anisotropy in Ta|CoFeB|MgO ultrathin films

Journal Article · Wed Jan 28 00:00:00 EST 2015 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4906096· OSTI ID:22412995

Sinha, Jaivardhan; Gruber, Maria; Kodzuka, Masaya; Ohkubo, Tadakatsu; Mitani, Seiji; Hono, Kazuhiro; Hayashi, Masamitsu ^[1]

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1. National Institute for Materials Science, Tsukuba 305-0047 (Japan)

We have studied structural and magnetic properties of Ta|CoFeB|MgO heterostructures using cross-section transmission electron microscopy (TEM), electron energy loss spectrum (EELS) imaging, and vibrating sample magnetometry. From the TEM studies, the CoFeB layer is found to be predominantly amorphous for as deposited films, whereas small crystallites, diameter of ∼5 nm, are observed in films annealed at 300 °C. We find that the presence of such nanocrystallites is not sufficient for the occurrence of perpendicular magnetic anisotropy. Using EELS, we find that boron diffuses into the Ta underlayer upon annealing. The Ta underlayer thickness dependence of the magnetic anisotropy indicates that ∼0.2 nm of Ta underlayer is enough to absorb the boron from the CoFeB layer and induce perpendicular magnetic anisotropy. Boron diffusion upon annealing becomes limited when the CoFeB layer thickness is larger than ∼2 nm, which coincides with the thickness at which the saturation magnetization M{sub S} and the interface magnetic anisotropy K{sub I} drop by ∼20%. These results show the direct role which boron plays in determining the perpendicular magnetic anisotropy in CoFeB|MgO heterostructures.

• OSTI ID: 22412995
• Journal Information: Journal of Applied Physics, Vol. 117, Issue 4; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANISOTROPY
ANNEALING
BORON
COBALT COMPOUNDS
DIFFUSION
ELECTRONS
ENERGY-LOSS SPECTROSCOPY
HETEROJUNCTIONS
INTERFACES
IRON BORIDES
LAYERS
MAGNESIUM OXIDES
MAGNETIC PROPERTIES
MAGNETIZATION
TANTALUM
THIN FILMS
TRANSMISSION ELECTRON MICROSCOPY