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Magnetoelectric effects in the artificial LSMO/PZT multiferroics.
Robert Kruk, Philipp M. Leufke, Christian Reitz, Horst Hahn
Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT)
Hermann-von-Helmholtz Platz 1, 76344 Eggenstein-Leopoldshafen, Karlsruhe, Germany
[email protected]
Abstract: In this work the results of studies on the magnetoelectric coupling in the artificial multiferroic
La1−xSrxMnO3/Pb(Zr,Ti)O3 (LSMO/PZT) heterostructures are presented. This multiferroic was – for the first
time – in-situ investigated in a superconductive quantum interference device (SQUID).
1.
INTRODUCTION
The concept of electronically tuneable properties
extends the field-effect principle (very well-known in
field-effect
transistors)
and
reversible
electrochemistry to control a broad spectrum of
physical properties in material systems. It has been
proposed that generation of the surface charge upon
the application of an electric field can lead to
significant changes in the material properties, even of
highly conducting systems, by judiciously exploiting
the high surface-to-volume ratios that are typical of
nanostructures [1].
Particularly, a dynamic and reversible control of
magnetic properties via applied electrostatic field
(surface charge) may be relevant to application areas
concerned with the manipulation, storage, and transfer
of information by means of electron spins. Indeed, it
has been reported for various nanostructures and
numerous ferro- and ferrimagnetic materials that an
applied surface charge can effectively affect exchange
interactions or magnetic anisotropy.
effect
dominated
magnetoelectric
coupling
mechanism, confirming the concept of electrostatic
hole doping of LSMO. For a small surface charge
concentration at low temperature, a remarkably large
tuning coefficient of about 4 μB/hole was determined
suggesting the inducement of a ferromagnetic to
antiferromagnetic phase transition in LSMO.
Simultaneously, a shift in the magnetic transition
temperature at higher surface charge concentration
indicates coexistence of the ferromagnetic and
antiferromagnetic phases at the LSMO/PZT interface.
The dynamic magnetization modulation, resulting
upon charging, is interpreted and discussed in the
context of the existing magneto-electronic phase
diagrams.
FIGURES
2. GENERAL TOPIC
This presentation provides background and
discusses key issues in practical realization of
electrically tuneable systems. Selected examples of
successful applications of the, surface-charge driven,
tuneability principle are presented, including
reversible control of magnetic states in strongly
correlated oxides and spinels. A notion of reversible
electrostatic doping (ED) and its relevance to the
dynamic control of magnetic properties will be
discussed. Further, this reversible control concept is
expanded, by means of polymer-based electrolytes,
beyond the thin film geometry to the entire class of
nanoporous and nanoparticulate structures.
3. CASE STUDY
The response of the magnetization to the electric
switching of the PZT ferroelectric film evidences a
purely electrostatic coupling mechanism with
negligible
piezoelectric
influence
(Fig.1).
Temperature dependence of the magnetic modulation
upon the ferroelectric stimulation indicates a field-
Fig.1. Magnetization response, Δm, of the strongly
correlated ferromagnetic La1−xSrxMnO3 to the electric
polarization, P, of the PZT ferroelectric.
REFERENCES
[1]. H. Gleiter, Scripta Mater. 44 (2000) 1161