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Monday, March 04

Directed Self-Assembly of Multiferroic Nanocomposites Using Patterned Templates

Ryan Comes, University of Virginia, Charlottesville, VA
Materials Science & Technology Division Seminar
11:00 AM — 12:00 PM, Building 4100, Room J-302
Contact: Ho Nyung Lee (hnlee@ornl.gov), 865.574.9782

Abstract

Multiferroic nanocomposites thin films composed of a ferromagnetic spinel oxide nanopillar and ferroelectric perovskite oxide matrix offer intriguing spintronic applications due to the magnetoelectric coupling between the matrix and pillar. CoFe2O4 (CFO) offers unique properties as a magnetoelectric material due to its large magnetoelastic response when strained. Previous work has shown that when CFO is co-deposited with BiFeO3 (BFO) nanostructured phase segregation occurs, with CFO pillars forming in a BFO matrix, and that electrical control of the magnetic anisotropy is possible. The CFO-BFO nanocomposite system has been proposed as a possible electrically-controlled spintronic logic or memory scheme. Other spinel-perovskite nanocomposites are also of interest, but the ability to control the growth of these materials to produce ordered arrays for device applications has thus far been illusory.

In this talk, I will discuss work I have performed at the University of Virgina as part of my dissertation to template the growth of CFO-BFO nanocomposites using a pre-patterned substrate via pulsed electron deposition (PED). The relatively new PED technique is similar to the more traditional pulsed laser deposition (PLD) approach but produces nanocomposites with somewhat different strain properties when compared to those grown via PLD in the literature. I will present analysis of the magnetic anisotropy of CFO-BFO nanocomposites grown using PED and explain the difference in magnetic properties that we see due to the different growth technique. Then I will discuss the new technique we have developed to direct the self-assembly of the CFO pillars in CFO-BFO nanocomposites using electron-beam lithography with pillar pitch spacing as small as 100 nm. Electron microscopy analysis has demonstrated that by templating the substrate with CFO islands before growth, we can pattern the epitaxial nanocomposite films and achieve similar crystal quality to the unpatterned films.