SIR Physics Investigation Abstract
CONTROLLED LARGE-SCALE SYNTHESIS AND MAGNETIC PROPERTIES OF SINGLE CRYSTAL COBALT NANORODS
Presenter:
Rohan Bhobe, Illinois Mathematics and Science Academy, 1500 West Sullivan Road, Aurora, IL, 60506
Mentor:
Dr. Vinayak Dravid, Northwestern University
Abstract:
Nanostructured magnetic materials are drawing considerable attention for their potential applications in ultra high-density magnetic data storage, sensors, and other electronic devices. One-dimensional structures such as nanorods and nanotubes exhibit interesting properties not characteristic of their bulk-material counterparts. Nanorods created from single crystalline ferromagnetic materials have the added advantage of being magnetically polarized in the same direction along the entire length of the nanorod. We report detailed synthesis studies and a novel procedure for the large-scale fabrication of single crystalline cobalt (Co) nanorods using thermally evaporated gold as a conducting electrode on a nanoporous anodic aluminum oxide (AAO) template. Cobalt was chosen over other ferromagnetic materials because of recommendation by previous literature. Electrodeposition was used to fabricate the cobalt nanorods inside the pores of the AAO membrane, after which a mild hydrofluoric acid (HF) solution was used to dissolve the AAO, yielding a large-scale ensemble of isolated Co nanorods. A preferred perpendicular anisotropy is observed in these nanorod arrays. Scanning electron microscopy and transmission electron microscopy (SEM and TEM, respectively) examination show clear evidence of single crystal metallic Co nanorods (approx. 100 nm in diameter and 10 µm in length). Superconducting quantum inference device magnetometer (SQUID-M) studies demonstrate ferromagnetic behavior in the cobalt nanorods. Magnetic properties indicate both coercivity and thermal activation volume increase with increasing nanorod length.