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Condensed Matter Seminars

ics Condensed Matter
Monday, March 23, 2009
11:00 AM
Physics Building, Room 313
Note special date.
Micky Holcomb [Host: Stu Wolf]
University of California, Berkeley
"Understanding Magnetism in Multiferroics"
Magnetoelectric multiferroics are materials that exhibit multiple order parameters, such as ferroelectricity and ferromagnetism. The potential for coupling between such order parameters and their manipulation through external stimuli (electric or magnetic fields) allows the exploration of novel physics and device functionalities. Among a large number of materials systems, the BiFeO3 system has emerged as an attractive model system, mainly because both the ferroelectric Curie temperature and the antiferromagnetic Neel temperature are well above room temperature. In order to understand magnetoelectric coupling, the individual order parameters must first be understood. While the ferroelectric order can be probed using conventional capacitive measurements as well as by scanned probe techniques (such as piezoforce microscopy) probing the antiferromagnetic order requires the use of optical probes, such as SHG and x-ray photoemission spectromicroscopy. Angle and temperature dependent absorption measurements using a state-of-the-art high-resolution photoemission microscope allowed imaging and direction determination of the order parameters in this multiferroic. These studies reveal the first observation of electrical control of antiferromagnetism and the extension to electrical control of ferromagnetism through exchange bias. Though this study, a generic method for separating order parameters in complex systems has been developed and applied.

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