Title: THE ROLE OF EDGE OXIDATION IN THE SWITCHING OF SOFT FERROMAGNETIC NANODOTS

Paul Morrow, June Lau

Affiliation: MSEL, Metallurgy Division, Magnetic Materials Group

Nanoscale magnetic tunnel junctions (MTJ) are expected to be key components in the next generation of magnetoresistive random access memory (MRAM). MTJ’s are composed of a hard ferromagnetic (reference) layer, an insulating barrier, and a soft ferromagnetic (switching) layer. As the size of these devices shrinks to the extreme nanoscale (i.e., below 50 nm), the role of defects becomes increasingly important, and they can assume the dominant role in the uniformity of the switching behavior. Some primary types of defects include edge/interface roughness, random grain mosaics, and process-dependent artifacts that invariably produce variations in the local magnetic properties (i.e., anisotropy and magnetization).

In this work we investigate the effect of edge oxidation in the magnetic switching behaviour of the soft ferromagnetic layer by fabricating Ni:80Fe:20 nanodots (30 nm diameter) and ellipses (60 nm × 30 nm). The nanodots/ellipses were deposited by either evaporation or sputtering, and pattern transfer was accomplished via additive or subtractive techniques. The effect of oxidation on the switching behavior is determined by hysteresis measurements made using a superconducting quantum interference device vibrating sample magnetometer (SQUID-VSM), and the degree of oxidation is determined by transmission electron microscopy (TEM). The TEM results are used as input parameters for the object-oriented micromagnetic framework (OOMMF) code developed here at NIST, and the simulated magnetic behavior is used to aid interpretation of SQUID-VSM results. Together, these experimental and simulation studies allow a quantitative link to be made between edge oxidation and switching behavior of the free layer in nanoscale magnetic devices.  

CATEGORY:

Materials

Name: Paul Morrow

Metallurgy Division, MSEL

B140, Bldg. 223, MS 8552

Tel: 301-975-4923

Fax: 301-975-4553

Email: paul.morrow@nist.gov

Sigma Xi member?    No

Mentor’s Name: June Lau/Robert Shull

Metallurgy Division, MSEL

B142/B150, Bldg. 223, MS 8552

Tel: 301-975-5711/6035

Fax: 301-975-4553

Email: june.lau@nist.gov/robert.shull@nist.gov

Is your mentor a Sigma Xi Member?     Yes