AVS 59th Annual International Symposium and Exhibition
    Magnetic Interfaces and Nanostructures Wednesday Sessions
       Session MI+OX-WeA

Paper MI+OX-WeA2
Magnetic Properties of Cobalt and Permalloy Thin Films Grown on Self-Assembled Monolayers by Physical Vapor Deposition

Wednesday, October 31, 2012, 2:20 pm, Room 006

Session: Spintronics, Magnetoelectrics, Multiferroics
Presenter: G.J. Szulczewski, The University of Alabama
Authors: G.J. Szulczewski, The University of Alabama
S. Schafer, The University of Alabama
B. Khodadadi, The University of Alabama
T. Mewes, The University of Alabama
J. Kreil, The University of Alabama
E. Ellingsworth, The University of Alabama
K. Anderson, The University of Alabama
Correspondent: Click to Email
In this talk we will present results from a study to understand how terminal functional groups in self-assembled monolayers (SAMs) influence the growth and subsequent magnetic properties of Co and NiFe (permalloy) thin films. Self-assembled monolayers were made from both aryl and alkyl carboxylic acids adsorbed onto oxidized aluminum surfaces. The SAMs were characterized by contact angle measurements and x-ray photoelectron spectroscopy. The magnetic properties of the thin films were characterized by ferromagnetic resonance spectroscopy. In general we find that reactive functional groups, for example thiols, cause the metals to grow as continuous films. In contrast, deposition of the metals onto non-reactive functional groups, for example methyl, leads to penetration of metal atoms through the SAM and cluster formation. The permalloy films are superparamagnetic below ~ 4 nm, while Co films are ferromagnetic at room temperature. The coercivity of the films is also found to vary with functional group. In the case of halide substituents, for example, flouro, chloro, bromo, and iodo on the aryl carboxylic SAMs, there is also a correlation between the magnetic properties of cobalt thin films and the strength of the carbon-halogen bond energy. Cobalt deposited onto SAMs with terminal C-F bonds tends to be non-reactive, while reactive toward C-I bonds. Not only do these reactivity patterns influence the magnetic properties of the thin film, but also they result in a measurable change in the resistance of tunnel junctions bearing these SAMs.