Upload
others
View
6
Download
0
Embed Size (px)
Citation preview
StructualStructual and Magnetic Properties of and Magnetic Properties of NanocrystallizedNanocrystallized TrantitionTrantition--Metal Oxides.Metal Oxides.
Hiroshi Kira(2004.8.1~)
Tohoku Y. Murakami, H. Tamura, Y. AndoUniversity T. Takahashi、M. Onodera
K. TsudaK.Oyama
Shizuoka Y. YamazakiUniversity
Kyushu H. IdeguchiUniversity
本研究における階層融合本研究における階層融合
Moleculemolecular
orbital
Electric structureLattice
原子・分子と凝縮物質の融合領域原子・分子と凝縮物質の融合領域
本研究における階層融合本研究における階層融合
Moleculemolecular
orbital
Electric structureLattice
???Nano crystal
原子・分子と凝縮物質の融合領域原子・分子と凝縮物質の融合領域
MetalMetal Strongly CorrelatedStrongly CorrelatedElectron System Electron System
Ex) Alkali Metal Ex) Transition metal oxides
0
0.5
1
1.5
0 2 4 6 8 10
Mag
netiz
atio
n (e
mu/
cm3 )
Temperature (K)
K5.0
/K12-LTA
M-T 20G
Potassium clusters arranging in simple cubic structure
Tc~6K Ferromagnetic transition
KK5.05.0/K/K1212--LTALTASpherical well potential
Strongly CorrelatedStrongly CorrelatedElectron System Electron System
Charge
Spin Orbital
site 1 site 2
site 3site 4
NanoNano--crystallized crystallized Strongly CorrelatedStrongly CorrelatedElectron System Electron System
1~10nm
Clarify the electronic states of nano-crystallized matter
ProblemsProblems
・・ Synthesis of the nano-crystallized transitional metal oxide
・ Stability ・ Size-distribution・ Amounts
1~10nm→MCM-41
PurposePurpose
30Å (30~80Å)
SiO2~5Å
102 ~
103 n
mStructure of MCMStructure of MCM--4141
Hexagonal NanomaterNanomater sized glass tube sized glass tube
LaMnOLaMnO33Perovskite Structure
LaOMnO2LaOMnO2LaOMnO2LaO
LaMnO3Canted Antiferromagnet
( TN=141K)
T.Sato, 2003(Tohoku University)
Preparation of LMO/MCMPreparation of LMO/MCM--4141
1. MCM-41+ La and Mn Nitrate solution
La and Mn nitrate is introduced into 1-d channel of MCM-41
Dried
2. Annealing (700℃, 20h, Oxygen atmosphere)La(NOLa(NO33))33 ++ Mn(NOMn(NO33))22 →→ LaMnOLaMnO33 + 5NO+ 5NO22 + O+ O22
Pristine Annealed
Magnetic properties of LMOMagnetic properties of LMO//MCMMCM--4141
・
0
0.005
0.01
0.015
0.02
0.025
0 50 100 150 200 250 300
試料①試料②試料③単結晶※強度は任意倍
Magnetization [
µ B/ion]
Temperature [K]
LMO/MCM-41M-T at 1000G
・Tc = 270 K??LaMnO3+δ : Tc=130K – 160K
Tc270K150K75K
Three Types FM TransitionsThree Types FM TransitionsTcTc=75K,150K,270K=75K,150K,270K
0 20 40 60 80 100
LMO/MCM-41LMO Bulk
Intensity (Arb. Units)
2Theta (deg)
2004.11.05 PF BL-1ALMO/MCM-41 XRDRT λ=1.409Å
XX--Ray Powder Diffraction AND TEM ImageRay Powder Diffraction AND TEM Image
Energy
Energy
0 20 40 60 80 100
Intensity
2Theta (deg)
RT λ=1.409Å
117Å
(112),(200)
138Å
(202)
96Å
(201), (004)
62Å
(224)
81Å
(024),
(312), (
204)
・ LMO nano crystal ・ No bulk phase LMO→Observed FM transition corresponding to the nano crystal?
XX--Ray Powder Diffraction AND TEM ImageRay Powder Diffraction AND TEM Image
0
0.5
1
1.5
2
2.5
3
3.5
0
0.05
0.1
0.15
0.2
0.25
0.3
0 50 100 150 200 250 300
800℃ 780℃770℃ 760℃740℃700℃
Magnetization (emu/g)
Temperature (K)
2005.02.03-07 LMO/MCM-41(25v%) H=1kG,ZFC
Magnetization (μB/Mn)
酸素流中・20h処理温度依存性
0 10 20 30 40 50 60 70 80
Intensity (arb. units)
2Theta (deg)
2005.02.11 KEK PF BL-1ALMO/MCM-41 O2Flow 20h
λ=1.408Å
800℃
780℃
770℃
760℃
740℃
LMO Bulk
Optimization of the synthetic condition Optimization of the synthetic condition 11
Magnetization X-Ray Powder Diffraction
770℃で最も大きい磁化
Observed FM transition (Tc=280K)corresponding to the nano crystal
760℃以上ではLa2Si2O7
Optimization of the synthetic condition 2Optimization of the synthetic condition 2
0
1
2
3
4
0 10 20 30 40 50 60 70 80
I (×
105 Counts)
2Theta (deg)
2005.02.14 KEK PF BL-1BLMO/MCM-41
λ=1.408Å83Å
92Å
74Å
74Å
57Å
Annealed at 750℃
・ Peaks of LMO Nano Crystal
・Size of the nano crystal →60~100Å
Succeeded in Succeeded in ddevelopeveloppingping the the method of method of nanonano--crystallize the crystallize the
transition metal oxidestransition metal oxides
Magnetism of LMO/MCMMagnetism of LMO/MCM--4141
Three types of ferromagnetism
0
0.5
1
1.5
2
2.5
3
3.5
0
0.05
0.1
0.15
0.2
0.25
0.3
0 50 100 150 200 250 300
800℃ 780℃770℃ 760℃740℃700℃
Magnetization (emu/g)
Temperature (K)
2005.02.03-07 LMO/MCM-41(25v%) H=1kG,ZFC
Magnetization (μB/Mn)
酸素流中・20h処理温度依存性
0
0.005
0.01
0.015
0.02
0.025
0.03
0 50 100 150 200 250 300
Magnetization (μ
B/ion)
temperature(K)
LMO/MCM-41M-T at 1000G
270~280K
150K75K
Three types of LMO Three types of LMO nanonano crystalscrystals
Electronic states of Electronic states of nanonano crystals in crystals in LMO/MCMLMO/MCM--4141
Magnetism of LMO/MCMMagnetism of LMO/MCM--4141
--11
((LaOLaO))
(Mn(Mn3+3+OO22))
((LaOLaO)) +1+1
+1+1
Amounts of introduced hole
1.TC = 270 K
2.TN = 150 K
3.TN = 75 K
δ = 0.1 – 0.2hole dope
δ = 0.1 – 0.2carrier dope
δ = 0
~30Å10-15 Layers????
Nano-crystallizedLaMnO3
Limited Size
Carrier dope
TiOTiO2 2 / MCM/ MCM--4141
0
1000
2000
3000
4000
5000
10 20 30 40 50 60 70
5%10%TiO2
I (co
unts
)
2Theta (deg)
TiO2/MCM-41TiO2 Cataryst
XX--ray powder diffractionray powder diffractionTiO2 nano clusters realized
works with UV light
Nanocrystal TiO2Visible light??
ConclusionConclusion
Succeeded in preparation of LaMnO3nano crystalsSucceeded in Succeeded in ddevelopeveloppingping the method of the method of nanonano--crystallize the crystallize the transition metal oxidestransition metal oxides
ResultsResults
high Tc of FM Transition in LaMnO3/MCM-41Size effects acts the effective charge transferTiO2/MCM-41 nano crystalsMnO2/MCM-41
Clarify the electronic states of nano-crystallized matterPurposePurpose
Structual and Magnetic Properties of Nanocrystallized Trantition-Metal Oxides.本研究における階層融合本研究における階層融合PurposeStructure of MCM-41LaMnO3Preparation of LMO/MCM-41