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Multiferroic Mechanisms in Lead Based Complex Perovskite Oxides
*
José Antonio Eiras
Federal University of São Carlos, Physics Department Rod.
Wash. Luis km 235, São Carlos/SP – 13565-905, Brazil
*e-mail: [email protected]
Since the experimental confirmation of magnetoelectric effect (ME) in Cr2O3, more than half century ago,
innumerous investigations have been devoted to predict and describe mechanisms and to improve the
magnitude of the ME coupling. Electrons on the crystalline lattice should mediate the coupling between
electric polarization (P) and magnetization (M) in solids. Magnetoelectric effect can be “amplified” by
the simultaneous occurrence of (anti)ferromagnetism and ferroelectricity, in the so-called multiferroic
materials. Complex multiferroic oxides have attracted increasing attention in recent years due to their
possible new fundamental physics and possibilities to improve the ME coupling. In fact, concerning about
the last topic, despite microscopic origin of magnetism is the same in all magnets; several different
microscopic sources of electric polarization (ferroelectricity) can be considered, and accordingly one
different types of multiferroics. Materials in which the magnetic and ferroelectric orders are
independently established display commonly weak ME coupling. On the other side, multiferroics with
spin order induced ferroelectricity (‘improper’ ferroelectrics), in which the ME coupling is obviously
intrinsic, can present higher ME coupling. Both mechanisms can coexist in actual multiferroics. One
direction to investigate multiferroics, with the above described characteristics, is to explore polar (FE
and/or pyroelectric) crystals which host magnetic elements, responsible for the establishment of
ferromagnetic, ferrimagnetic or AF orders.
In this presentation will be presented and discussed experimental results (dielectric, pyroelectric,
magnetic and elastic results) from lead oxide based complex perovskites (Pb(Fe2/3W1/3)O3+PbTiO3 –
PFW-PT). PFW present “classical” ferroelectric and antiferromagnetic orderings around 180 K and 340
K, respectively. The gradual addition of PT to PFW enables to “tune” the temperatures of both orderings,
increasing the intrinsic ME coupling. On the side, high temperature measurements (magnetic
pyroelectric) show that PFW presents weak ferromagnetism and multiferroic characteristics, which can be
related with spin order induced ferroelectricity (multiferroic type II).
Curriculum Vitae
Name
Jose Antonio Eiras
Professional
Address
Universidade Federal de São Carlos, Centro de Ciências Exatas e
de Tecnologia, Departamento de Física.
CAIXA POSTAL 676
13565-905 - Sao Carlos, SP - Brasil
Phone: (16) 33519725 Fax: (16) 33614835
[email protected]
Formal Education/Degree
1980 - 1985
Ph.D. in Metallkunde und Metallphysik .
RWTHA Aachen University, RWTHA, Germany. Year of degree:
1985.
Advisor: Prof Dr. h.c. Kurt Lücke.
Physical Metallurgy
1977 - 1980
Master´s in Physics
Universidade de São Paulo, USP, Brasil. Year of degree: 1980.
Advisor: ProfDr. Milton F. de Souza.
Physics of Condensed Matter
1975 - 1976
Bachelor in Physics
Universidade de São Paulo, USP, Brasil.
1972 - 1974
Licentiate in Physics
Universidade Federal de São Carlos, UFSCAR, Brasil.
Professional Activities:
Contract
1976 – Present
Actual Positions:
Universidade Federal de São Carlos, UFSCAR, Brasil.
Physics Department
Professor / Researcher. Hours/Week: 40 - Exclusive
dedication
Ø Full Professor at the Physics Department –
UFSCar/Brasil
Ø Researcher Fellowship – National Council of Scientific
and Technological Development - CNPq : Degree 1A
Ø Member: Academy of Science of the São Paulo State.
Areas of Interest
Major Areas: Physics of Condensed Matter and Materials
Science
Subjects of Interest
Synthesis of Ceramic Ferroic Materials (ferroelectrics and
multiferroics - bulk or nanostructured), characterization
(ferroelectric, electric, dielectric, piezoelectric and mechanical
properties) and phenomenology (ferroelectric domain wall
dynamics, phase transitions).
Member of Editorial Board
2000 - Present
Scientific Journal: Ferroelectrics
2000 – Present
Scientific Journal: Cerâmica (Brasil)
2009 – Present
2015 - Present
Reviewer
Scientific Journal: Journal of Advanced Dielectrics
Associate Editor: Materials |Research (Brasil)
Reviewer of scientific journals in the areas of Physics of
Condensed Matter, Materials Science and Ultrasonic
Transducers and Applications.