terahertz spectroscopy of electromagnons in multiferroics ashida lab. saito tadtaka 1
TRANSCRIPT
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Terahertz spectroscopy of electromagnons in Multiferroics
Ashida lab.Saito Tadtaka
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Contents
• Introduction ---Multiferroic materials ---The mechanism of Electromagnon’s excitation
• Experiment ---Experimental set up ---Sample
• Results • Summary
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Multiferroics
E
H
P
M
Multiferroics are materials where ferroelectricity and ferromagnetism are inherently coupled.
The magnetization can be controlled by electric field of light.The polarization can be controlled by magnetic.
Introduction ---Multiferroic materials
3
Magnet Electric effect(ME effect)
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Magnet Electric effectAntisymmetry Dzyaloshinskii-Moriya interaction
)(, jiji SSeP
Ptotal //c
Spiral-spin-order
a
b
c
ji ,e
iS jSらせんスピン磁性
bc-spiral
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Introduction ---Multiferroic materials
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Electromagnon
Magnon can be excited by electric field of light.
MagnonSpin wave
Magnon is exited by magnetic field.
Multiferroics…
Electromagnon(2006)
RMnO3 R; rare-earth metalLow temperature, High H
5
Introduction ---electromagnon’s excitation
N.Kida. et al Opt. Soc 26 108794(2009)
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RMnO3Rare-earth-metal perovskite magnitesR; rare earth elements(Y, Eu, Tb, Dy, ・・・ )
M. Mochizuki, et al Phy. Rev. Lett.104.177206(2010). 6
Introduction ---electromagnon’s excitation
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Phase Diagram of Eu1-xYxMnO3
Spiral spin phase
Spontaneous polarization
Spin chirality
At ab-cycloidal…
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Introduction ---electromagnon’s excitation
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Super Exchange Interaction
c
jijic
b
jijib
yx
jijiabex JJJ
,,
,
,
SSSSSS
Introduction
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The modulation of this interaction results in electromagnon’s excitation.
Introduction ---electromagnon’s excitation
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E//a
abJ
abJ
abJ
abJ
E//b
abJ
abJ
abJ
abJ
Mechanism of Electromagnon
a
b
yx
jijiabex J
,
,
SS
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Introduction ---electromagnon’s excitation
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Experimental set up
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Experiment
• THz-TDS enables us to observe a waveform of ”E(t)” directly.• By using THz-TDS , both amplitude and phase of ”E(t)” are directly obtained.
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Y-type hexaferrite Ba2Mg2Fe12O22
Ferri magnetic proper screw Conical spin
Room temperature T<195K T<50K
Sample六方晶フェライト
11S. Ishiwata et al Science 319, 1643 (2008)
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Weak magnetic field( ~ 1T)H//[001]
Longitudinal conical spin
H(>3T)
H//[100]
Transverse conical spin
H( > 4T)
FerrimagneticProper screw
Ferrimagnetic
θ
(001)
(100)(120)
Transition of spin phase by weak magnetic field
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Sample
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Proper-screwConical Ferri
F
C
F
C
F
Spectra change
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Proper-screwConical Ferri
F
C C
FF
Sample
Electromagnon’s excitation was observed inconical spin order.
Spectra change by weak H
E//(001)
N. Kida et al Phy Rev B 83, 064422 (2011)
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Z-type hexaferrites Sr3Co2Fe24O41
Y-type Z-type 14
Sample
Y. Kitagawa, etc Nat. Mat. 9, 797(2010).
Polarization by ME effect at room temperature.
c
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Results
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Results
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Results
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Results
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Summary
• I introduced to my study toward observation of electromagnon’s excitation at room temperature.
• We observed the change of spectrum by the direction of light polarization in Z-type hexaferrites Ba3Co2Fe24O41 at room temperature.
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Summary