mitglied der helmholtz-gemeinschaft giorgi khazaradze tbilisi, july10, 2014 study of hexaferrite ba...
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Hel
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aft Giorgi Khazaradze
Tbilisi, July10, 2014
Study of hexaferrite Ba0.6Sr1.4Zn2Fe12O22 by EPR technique
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Ferroelectric and Ferromagnetic orderings Schematic picture of Multiferroic
What is Multiferroics?
Read withGMR
Multiferroic
Write with avoltage
MF-RAM
[M. Bibes and A. Barthélémy, Nat. Mater. 7, 425 (2008)]D. Khomshii, Physics 2, 20 (2009)
P=α HM=α E
Magnetoelectric effect
Pij=eij x (si x sj) Dzyaloshinskii-Morya interaction
Cycloidal spin ordering
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Schematic crystal structures of hexaferrites. The (110) cross section views of an M-type (Ba,Sr)Fe12O19, W-type (Ba,Sr)Me2 Fe16O27, X-type (Ba,Sr)2 Me2Fe28 O46 , Y-type (Ba,Sr)2Me2
Fe12O22, Z-type (Ba,Sr)3Me2 Fe24 O41 , and U-type (Ba,Sr)4Me2Fe36O60 with the c axis vertical.
The (Fe,Me)-O-(Fe,Me) bond angles surrounded by dashed blue ellipsoids are strongly affected by the ratio of Sr to Ba.
Kimura et al., Annu. Rev. Condens.Matter Phys. 2012. 3:93–110]
Type of hexaferrites
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a) cristal sructure, b-d magnetic structure of Y-type hehaferrite.b) The proper-screw, c) the transverse-conical, d) the conical
Kimura et al., Annu. Rev. Condens.Matter Phys. 2012. 3:93–110]
a b c d
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Magnetic field dependence of electric polarization at different Temperatures and magnetic phase diagram of High-T MF hexaferrite Ba0.5Sr1.5Zn2Fe12O22 with magnetic field perpendicular to the c axis
T. Kimura et al. Phys Rev. Lett. 94,137201 (2005)
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Short description of EPR
• Zeeman splitting by magnetic field.• 9.6 GHz electromagnetic wave is
absorbed.• Linewidth of EPR is caused by the
interaction between the ions.
Ez=h𝝂=gµβH
Ez −Zeeman energy
𝝂− 𝑡ℎ𝑒 𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑦 𝑜𝑓 the microwave field
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A. Maisuradze Aet al., Phys. Rev. Lett., 108, 247211 (2012).
Idea: apply electric field modulation and try to detect magnetic resonance in ME materials
H=H‘+HmSin(2π𝝂mt) H‘−𝑺𝒕𝒂𝒕𝒊𝒄 𝒂𝒑𝒑𝒍𝒊𝒆𝒅 𝒎𝒂𝒈𝒏𝒆𝒕𝒊𝒄 field
Hm−Modulation amplitude 𝝂m−Modulation frequency 𝝂m−100KHz
P(t)=PmSin(2π𝝂mt) P(t) –Detected absorbed
power
Schematic picture of the experiment and the Magnetic/Electric field directions
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Electric-field modulated FMR is selectively sensitive to Magnetoelectric coupling in Cu2OSeO3
A. Maisuradze et al., Phys. Rev. Lett., 108, 247211 (2012).
Temperature dependence of FMR signals of single-crystal Cu2OSeO3
detected using the MFM technique and the EFM technique
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Ferromagnetic resonance in Y-type hexaferrite Ba0.6Sr1.4Zn2Fe12O22
Angular dependence of the resonance field
θ
C axis
H
0 2000 4000 6000 8000
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
T=293K
Ba0.6
Sr1.4
Zn2Fe
12O
22
FM
R S
igna
l, a.
u.
Magnetic Field, G0 15 30 45 60 75
1500
3000
4500
6000
7500
Res
onan
ce fi
eld,
G
Angle , Degree
B C
Ba0.6
Sr1.4
Zn2Fe
12O
22
T=293K
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Ferromagnetic resonance in Y-type hexaferrite Ba0.6Sr1.4Zn2Fe12O22 with Electric field modulation
2000 4000 6000 8000
-300
-200
-100
0
100
200
T=293K
Ba0.6
Sr1.4
Zn2Fe
12O
22
FM
R S
igna
l, a.
u.
Magnetic Field, G
500 1000 1500 2000 2500
0.05
0.10
0.15
0.20
0.25
Ba0.6
Sr1.4
Zn2Fe
12O
22
Am
plitu
de, a
.u
Electric field, V
Amplitude of firs FMR Line Amplitude of firs FMR Line
T=273K
FMR signal at Electric fieldThe amplitude of FMR signal as function Electric field
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Magnetic and Electric Field Modulated FMR (EFMR) in Ba0.6Sr1.4Zn2Fe12O22
0 2000 4000 6000 8000
-0.4
-0.2
0.0
0.2
0.4
Ba0.6
Sr1.4
Zn2Fe
12O
22
=600
T=293K
FM
R S
igna
l, a.
u.
Magnetic Field, G
Magnetic Electric
0 2000 4000 6000 8000
-0.4
-0.2
0.0
0.2
0.4
0.6
=900
T=293K
Ba0.6
Sr1.4
Zn2Fe
12O
22
FM
R S
ignal,
a.u
.
Magnetic Field, G
30 45 60 75 90 1051E-8
1E-7
1E-6
T=293K
Coupling at second FMR line Coupling at first FMR line
T=293K
Ba0.6
Sr1.4
Zn2Fe
12O
22M
agni
toel
ectr
ic c
oupl
ing,
Angle , Degree
Angular dependence of the Magnetoelectric (ME) coupling
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Summary and Conclusions• Ferromagnetic resonance (FMR) in Y-type hexaferrite
single crystal Ba0.6Sr1.4Zn2Fe12O22 was observed.
• Using electric field modulation FMR (EFMR) technique magnetoelectric coupling was observed in this compound.
• Magnetoelectric coupling was estimated, however it is week at room temperature.
• Magnetoelectric coupling was determined quantitatively as a function of temperature and magnetic field orientation.
• The next step would be to study this compound at lower temperatures and appropriate magnetic field range where electric polarization was observed by using Soft X-ray Scattering method.
Outlook
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Thanks for your Attention!