Browsing by Author "Scholl, A."

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Electrically controllable spontaneous magnetism in nanoscale mixed phase multiferroics
(2011-03-01)
He, Q.
;
Chu, Y. -H.
;
Heron, J. T.
;
Yang, S. Y.
;
Liang, W. I.
Magnetoelectrics and multiferroics present exciting opportunities for electric-field control of magnetism. However, there are few room-temperature ferromagnetic-ferroelectrics. Among the various types of multiferroics the bismuth ferrite system has received much attention primarily because both the ferroelectric and the antiferromagnetic orders are quite robust at room temperature. Here we demonstrate the emergence of an enhanced spontaneous magnetization in a strain-driven rhombohedral and super-tetragonal mixed phase of BiFeO(3). Using X-ray magnetic circular dichroism-based photoemission electron microscopy coupled with macroscopic magnetic measurements, we find that the spontaneous magnetization of the rhombohedral phase is significantly enhanced above the canted antiferromagnetic moment in the bulk phase, as a consequence of a piezomagnetic coupling to the adjacent tetragonal-like phase and the epitaxial constraint. Reversible electric-field control and manipulation of this magnetic moment at room temperature is also shown.
Nanoscale characterization of emergent phenomena in multiferroics
(2012-10-01)
He, Q.
;
Arenholz, E.
;
Scholl, A.
;
Chu, Y. -H.
;
Ramesh, R.
Multiferroics exhibit intriguing physical properties and in turn promise new device applications as a result of the coupling between their order parameters. In this review article, we introduce photoemission electron microscopy (PEEM) as a powerful tool to study multiferroicity with the capability of probing the charge, spin and orbital states of a material simultaneously with nanoscale spatial resolution and element sensitivity. Several systematical studies of ferroelectricity, antiferromagnetism, and multiferroicity using PEEM are discussed. In the end, we outline several challenges remaining in multiferroic research, and how PEEM can be employed as an important characterization tool providing critical information to understand the emergent phenomena in multiferroics. Published by Elsevier Ltd.
Probing the evolution of antiferromagnetism in multiferroics
(2010-04-01)
Holcomb, M. B.
;
Martin, L. W.
;
Scholl, A.
;
He, Q.
;
Yu, P.
This study delineates the evolution of magnetic order in epitaxial films of the room-temperature multiferroic BiFeO(3) system. Using angle-and temperature-dependent dichroic measurements and spectromicroscopy, we have observed that the antiferromagnetic order in the model multiferroic BiFeO(3) evolves systematically as a function of thickness and strain. Lattice-mismatch-induced strain is found to break the easy-plane magnetic symmetry of the bulk and leads to an easy axis of magnetization which can be controlled through strain. Understanding the evolution of magnetic structure and how to manipulate the magnetism in this model multiferroic has significant implications for utilization of such magnetoelectric materials in future applications.