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Epitaxial Bi5Ti3FeO15-CoFe2O4 pillar-matrix multiferroic nanostructures
Akira Imai1, Xuan Cheng, Huolin L Xin
1Materials and Structures Laboratory, Tokyo Institute of Technology , 4259 Nagatsuta, Midori-ku Yokohama 226-8503, Japan.
ACS Nano
|November 13, 2013
Summary
This study demonstrates novel lead-free magnetoelectric nanocomposites using cobalt iron oxide (CoFe2O4) pillars within a bismuth titanate (Bi5Ti3FeO15) matrix. These structures exhibit promising ferromagnetic and ferroelectric properties for advanced applications.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Ferroelectric bismuth layered perovskites (e.g., Bi5Ti3FeO15) and ferromagnetic spinels (e.g., CoFe2O4) are key functional materials.
- Developing lead-free magnetoelectric composites is crucial for next-generation electronic devices.
- Epitaxial growth of complex oxide nanostructures presents unique challenges and opportunities.
Purpose of the Study:
- To fabricate and characterize epitaxial self-assembled ferro(i)magnetic/ferroelectric nanocomposites.
- To investigate the magnetoelectric coupling and ferroelectric properties influenced by nanostructure morphology.
- To explore the potential of these lead-free materials for magnetoelectric applications.
Main Methods:
- Epitaxial growth of CoFe2O4 (CFO) pillars within a Bi5Ti3FeO15 (BTFO) matrix on SrTiO3 substrates.
- Piezoresponse force microscopy (PFM) to probe ferroelectric domain switching and polarization.
- Phenomenological Landau-Ginzburg-Devonshire (LGD) thermodynamic modeling to understand stress effects.
- Vibrating sample magnetometry (VSM) to analyze magnetic properties.
Main Results:
- Successfully fabricated vertically aligned CFO pillars (∼50 nm diameter) within a BTFO matrix up to 50% volume fraction.
- Observed strong in-plane and weak out-of-plane ferroelectricity in BTFO, contrary to bulk properties.
- Demonstrated robust ferromagnetism in CFO pillars with minimal degradation of saturation magnetization.
- LGD modeling indicated radial stress from CFO pillars significantly influences BTFO ferroelectric phases.
Conclusions:
- The BTFO-CFO nanocomposites exhibit promising coexisting ferroelectric and ferromagnetic properties.
- Nanopillar-induced stress is a critical factor modulating the ferroelectric behavior in the matrix.
- These lead-free nanocomposites represent a viable system for developing novel magnetoelectric devices.
