MSE Seminar - Dr. John Read, National Institute of Standards and Technology

Friday, September 11, 2009
1:00 p.m.
Room 2108, Chemical and Nuclear Engineering Bldg.
Annette Mateus
301 405 5207
amateus@umd.edu

"High Magnetoresistance Mg-B-O Tunnel Junctions with Ni-Fe-B and Fe-Co-B Free Electrodes"

High tunneling magnetoresistance (TMR) in MgO magnetic tunnel junctions (MTJs) is key to the realization of next generation magnetic random access memory (MRAM). The best results in the thin barrier, < 1.5 nm, low resistance-area (RA) (< 100 Ωum)2) regime required for MRAM applications are generally obtained with sputter deposition of MgO between amorphous Co-Fe-B electrodes that crystallize during annealing. This deposition process partially oxidizes the base electrode, resulting in Mg-B-O barrier formation with ~5-10% B trigonally coordinated with O (BO3). To optimize the utility of high TMR MTJs for MRAM applications, specifically spin-transfer torque switching based MRAM applications, an ideal free layer material is required. Permalloy (Py), Ni81Fe19?, which has essentially no magnetostriction, low microcrystalline anisotropy, saturation magnetization (MS), coercivity, and damping, is such a material. We demonstrate that annealed Co-Fe-B / Mg-B-O / Ni-Fe-B MTJs have textured Py-like free electrodes. These MTJs achieve high TMR values (~150%) in the low RA regime (< 20 Ωum)2), provided the Ni-Fe-B alloy is sufficiently B rich. I will present correlated electronic, chemical, and magnetic studies that illuminate the behavior of these MTJ thin film stacks with a focus on their potential utility in MRAM applications.

Audience: Public 

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