Competing Interface and Bulk Effect-Driven Magnetoelectric Coupling in Vertically Aligned Nanocomposites.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Room-temperature magnetoelectric (ME) coupling is achieved in artificial multilayers and nanocomposites.
• While studied in multilayers, ME coupling in vertically aligned nanocomposites (VANs) remains largely unexplored.
• Theory predicts VANs offer significantly larger ME coupling coefficients than multilayer structures.

Purpose of the Study:

• To investigate and report strong transverse and longitudinal ME coupling in epitaxial BaTiO3:CoFe2O4 VANs.
• To explore the mechanisms governing ME coupling in VANs, focusing on interfacial effects.
• To provide physical insights into vertical interface coupling applicable to various nanocomposites.

Main Methods:

• Fabrication of epitaxial BaTiO3:CoFe2O4 vertically aligned nanocomposites (VANs).
• Measurement of ME coupling using optical second harmonic generation and piezoresponse force microscopy under magnetic fields.
• Phase field simulations to analyze the dependence of ME coupling on interfacial area and pillar size.

Main Results:

• Strong transverse and longitudinal magnetoelectric coupling was observed in the BaTiO3:CoFe2O4 VANs.
• ME coupling strength was found to be highly dependent on the vertical interfacial area, controlled by pillar size.
• The coupling is governed by a competition between vertical interface coupling and bulk volume conservation effects.

Conclusions:

• Vertically aligned nanocomposites exhibit significant room-temperature magnetoelectric coupling.
• The interface area and interplay between interface/bulk effects are critical for optimizing ME coupling in VANs.
• The findings offer general physical insights into vertical interface coupling for diverse nanocomposite functionalities.