Aerospace & Defense Technology - February 2021 - 34

Tech Briefs

Reconfigurable Electronics Based on Multiferroics and
Nanomagnetism
Research could lead to the development of new materials with large magnetoelectric (ME) coupling
for next-generation multifunctional devices, including, multi-state (neuromorphic-like) circuits and
memories, and E-field tunable microwave resonators for secure communications.
Air Force Research Laboratory, Arlington, Virginia

BFO Matrix

CFO Pillar

Out-of-Plane

ultifunctional magnetoelectric materials with high exchange represent a missing " holy grail " of materials
physics. To combine polarization and
magnetization in the same solid is
nothing short of actually controlling
the fundamental nature of electromagnetism in matter. Although magnetoelectricity (ME) is an intrinsic phenomenon in some natural materials at low
temperature, such single-phase materials suffer from an extremely weak ME
exchange.
In contrast, composites consisting of
magnetostrictive and piezoelectric
phases can feature dramatically larger
ME coefficients. This proposed program
focuses on achieving the disruptive potential of emerging multifunctional
magnetoelectrics, and in so doing lay
the foundations for their use as a materials platform that would benefit future
AFOSR applications.
The purpose of this research is to develop new ME thin-layers. Efforts focus
on heterostructures grown on piezoelectric single crystal substrates. The program objectives are to (1) optimize epitaxial ME thin layers with regards to the
influence of film composition, epitaxy,
deposition parameters, defects and substituents; and influence of substrate
composition with proximity to the
morphotropic phase boundary (MPB)
and crystallographic orientation; (2)
study the reconfigurable properties of
these ME heterostructures and nanostructures under multiple fields for application in logic, memory, and tunable
microwave applications; and (3) understand EM interactions on the nanometer scale in these two phase systems.
The anticipated outcome and impact
of this effort will be realized in the development of new materials with large
magnetoelectric (ME) coupling for nextgeneration multifunctional devices, including, multi-state (neuromorphic-

SRO
PMN-PT (100)

In-Plane

Schematic of the BFOCFO/SRO/PMN-PT heterostructure. Out-of-plane is perpendicular to the sample surface, and in-plane is parallel to the sample surface.

like) circuits and memories, and E-field
tunable microwave resonators for secure communications.
In general, self-assembled BiFeO 3CoFe2O4 (BFO-CFO) thin films were deposited on (100) Pb(Mg 1/3Nb 2/3) 0.62
Ti0.38O3 (PMN-38PT) single crystal substrates. These heterostructures were used
for the study of real-time changes in the
magnetization with applied DC electric
field (EDC). With increasing EDC, a giant
magnetization change was observed
along the out-of-plane (easy) axis. The
induced magnetization changes of the
CFO nanopillars in the BFO/CFO layer
were about delta M=80%. A giant converse magnetoelectric (CME) coefficient
of 1.3 × 10-7s/m was estimated from the
data. By changing EDC, multiple (N ≥ 4)
unique possible values of a stable magnetization with memory were found on removal of the field.
To be specific, a SRO buffered BFOCFO nanopillar structure was deposited
on (100) PMN- 38PT substrates, e.g. BFOCFO/SrRuO 3/PMN-38PT, as schematically shown in the accompanying figure.
A 65%BFO-35%CFO composition ratio

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Cov

ToC

was chosen. All thin films were deposited
by pulsed laser deposition.
The single crystal PMN-38PT substrates were grown by the Shanghai Institute of Ceramics Chinese Academy
Sciences. The crystal structure was determined by X-ray diffraction (XRD,
Philips X'Pert system) line and mesh
scans. Magnetic hysteresis loops were
recorded using a vibrating sample magnetometer (VSM, Lakeshore 7300 series)
along both out-of-plane (perpendicular
to the sample surface) and in-plane
(parallel to the sample surface) directions. Atomic force (AFM) and magnetic
force microscopy (MFM) images were
obtained (Dimension 3100, Vecco),
which were used to study the surface
and magnetic domain structures.
This work was done by Dwight Viehland
and Jie-Fang Li of Virginia Polytechnic Institute and State University for the Air Force
Office of Scientific Research. For more information, download the Technical
Support Package (free white paper) at
www.aerodefensetech.com/tsp under
the Electronics & Software category.
AFRL-0301

Aerospace & Defense Technology, February 2021

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