giant magneto-caloric effect research in vietnam - the personal impact of np thuy tribute to prof....
TRANSCRIPT
Giant Magneto-Caloric Effect Research in Vietnam -
The Personal Impact of NP Thuy
Tribute to Prof. Nguyen Phu Thuy
Motivations
Development of magnetic refrigeration• Demonstration of an Active Magnetic Refrigerator [C.
Zimm et al. (1996), Zimm et al., Adv. Cryogen. Eng. 43(1998)1759]: – 3 kg pure Gd metal – 5 T superconducting magnet – Cooling power: 600W, Efficiency: 60%.– New design (possibly a Stirling Cycle prototype with
Nd2Fe14B magnet)
• Discovery of the Giant MCE [Gschneidner, Pecharsky et al. (1997), IOWA State Univ. News Release (2001)]: GMCE material Gd5(Si1-xGex)4
• Magneto-Caloric Effect - (MCE) is the change in temperature of a magnetic material due to the adiabatic change of the external applied magnetic field. Application of the MCE: Magnetic refrigeration.
VNU Key Research Project(QGTD-00-01)(NP Thuy formulated, proposed and got approved)
Title: Fabrication and investigation of materials with giant magneto-caloric effect for use in a new generation of magnetic refrigerators.Proposer and Coordinator: Nguyen Phu Thuy
Duration: 2 (two) years Budget: 300 Millions VND (about 20,000 US$ at that time)
Contents of the Research
• Investigation on the off-stoichiometric Gd5(SiGe)4 systems
• Investigation of the R5(SiGe)4 systems
• Other intermetallic alloy systems• Perovskite and other like compounds• Experimental methodology and techniques• Magnetic Cooling Effect demonstration (Cryo-Lab, CMS, Solid State Dep, Faculty of Chemistry, ITIMS,
HUT Chemistry Faculty, IMS and many others participated)
Results in R5(Si,Ge)4 systems
Gd5(SixGe1-x)4 system with excess Gd, off-stoichiometric compounds, data measured on SQUID and Pulsed Field Magnetometer (PFM) for comparison
-S
ma
g[J/k
g·K
]
B = 5T
MCE Determination: Isothermal magnetisation curves measured on PFM do not show enough details from the magnetisation of the materials in the temperature range around the Curie Transition Temperature.
Magnetic field(T)
0 1 2 3 4 5 6
Ma
gn
etiz
ati
on
(em
u/g
)
0
20
40
60
80
100
120
140
160
180
148 K
77 K
170 K
§ êng liÒn nÐt: PFM§ êng cã ®iÓm: SQUID
Gd5(SixGe1-
x)4
x=0.2525
The R5Si2Ge2 Compounds (proceedings of APPC 2000 conference) Replacing Gd by Rare Earths in R5Si2Ge2
All compounds formed in similar crystal
structure as that of Gd5Si2Ge2.
Magnetic Properties varied with R: either
ferro- or antiferromagnetic structure, complex
magnetic structure at low temperatures.
Spin reorientation transition observed in
Er5Si2Ge2.
Giant MCE in Tb5(SixGe1-x)4, associated with
structural and other field-induced phase
transitions.
Spin reorientation in Er5Si2Ge2
(Collaboration with Ho of Cincinatti University)
T (K)
0 10 20 30 40
S (
J /
mo
l K
)
a
1
2
3
4
20
40
60
80
100
120
Er5Si2Ge2
(a)
(b)
C /
T (
J /
mo
l K
2)
Er5Si2Ge2
Lu5Si2Ge2
Lu5Si2Ge2
(a)
T(K)
0 50 100 150 200 250 300
1/
Tkg
/ A
m2
0.0
0.2
0.4
0.6
0H = 0.01T
T(K)
0 10 20 30 40
1/ (
Tkg/
Am
2 )
0.00
0.02
0.04
0.06
Er5Si2Ge2
1.5T
0.5T
0H = 0.01T
Stoichiometric Tb5(SixGe1-x)4 compounds, measured on SQUID and PFM
50 100 150 200 250 300 3500
4
8
12
16
20
24
28
32
36
40
Sm
ag [J/
kg
.K]
T [K]
x = 0.6 x = 0.6 - PFM x = 1
0
1
2
3
4
5
6
7
8
9
10
Tb5(SixGe1-x)4
B = 5 T x = 0.4
SM
ag[J
/kg
.K]
Giant MCE in the Tb5(SixGe1-x)4 system
10
100 150 200 250 300
0
4
8
12
16
20
24
28
32
ΔS
mag
[J/k
g·K
]
Temperature [K]
0
1
2
3
4
5
6
7
8
9Tb5(SixGe1-x)4
ΔB = 5 T
x = 0.6 x = 1
x = 0.5
x = 0.75
x = 0.4
ΔS
mag
[J/
kg
·K]
Results on the Tb5(SixGe1-x)4 system
Magnetic Order
0 50 100 150 200 2500
20
40
60
80
100
120
140
0 100 200 3000.0
0.1
0.2
0.3
B = 1 T
T [K]
B = 1 T
B = 0.01 T
x13
x13Mag
net
isat
ion
[A
·m2 ·
kg-1]
Temperature [K]
FC
ZFC
ZFC FC
1/[
Tk
g/A
m2 ]
Temperature [K]0 50 100 150 200 250 300 350
0
25
50
75
100
125
150
175
200
B = 0.01TB = 5T
x 50
Tb5Si2.4Ge1.6
Mag
net
isat
ion
[A
·m2 ·
kg-1
]
Tb5Si2Ge2
Field-induced transition in Tb5(SixGe1-x)4
0 10 20 30 40
100
150
200
250
0 10 20 30 40100
150
200
Mag
neti
zati
on
[A
m2/k
g]
Magnetic field [T]
Tb5Si3Ge Tb5Si2Ge2
Magnetic field [T]
Mag
neti
zati
on
[A
m2/k
g]
Tb5Si2Ge2
Structural Phase Transition in the vicinity of the Curie Temperature (TC) in the Tb5(SixGe1-x)4 system
Inte
nsit
y [
arb
. u
nit
s]
2 [degree]20 22 24 26 28 30 32 34 36 38 40 42
100K
110K
115K
120K
130K
150K
Tb5Si2.4Ge1.
6
Collaboration with TU Dresden
Temperature Dependence of the Lattice Parameters of Tb5Si2.4Ge1.6:
Orthorhombic below TC=150KMonoclinic above TC= 150K
50 100 150 200 250 300
7.44
7.46
7.48
7.50
Latt
ice p
ara
mete
rs [
Å]
Temperature [K]
7.70
7.72
7.7414.64
14.66
14.68bo (T)
am (T)
bm (T)
ao (T)
co (T)
cm (T)
TC = 150 K
TC = 150 K
Orthorhombic Lattice parameters of Tb5Si3Ge in the temperature range from 50 to 300 K. An anomaly (a kink in the curves) occurs at 210 K, its Curie Temperature.
100 150 200 250 300
7.42
7.43 a (T)Latt
ice p
ara
mete
rs [
Å]
Temperature [K]
7.69
7.70
7.71
7.72
c (T)
b (T)
14.62
14.63
14.64
50
TC = 210 K
Effect of Cooling Cycle
Temperature dependence of the electrical resistivity and the magnetization in magnetic field up to 1 T between 10 and 300 K of the compounds Tb5(SixGe1−x)4 with x=0.6, 0.75, and 1.0 were studied.
All samples exhibit irreversible changes in the electrical resistance on thermal cycling between room temperature and 10 K. The irreversible effect is reduced with increasing x from 0.6 to 1.0, and it is not observed in the magnetisation studies.
The resistance irreversible effect may be due to micro-cracks formed during the thermal cycling associated with the induced structural phase transition).
Important to application: working substance can be destroyed!
Collaboration with D. Yao (Taiwan)
MCE in the La1-xNdx(Fe,Si)13 sytems
- Giant MCE.
-TC above 200K.
- Metamagnetic phase transition.
-Main part of material is Fe, therefore cost advantage.
FWHM = 40 K
FWHM = 26 K
T2T1
MCE in RCo2 system
0
T [K]
-ΔS
Mag
[J/
kg
·K]
Er(Co1-xSix)2
RCo2 (R=Dy, Tb, Gd)
0.10
100 200 3000
10
20
30
40
0.15
x = 0
0.05
0.075
0.02
MCE in Perovskite Compounds La1-xAxBO3
(A= Ca,Sr,Pb,Ag,Na; B=Mn,Co,Cu,Cr)
- Ceramic materials, simple preparation technology. Low cost of materials.
- Reasonably high MCE, comparable to pure Gd.
- High TC from 260K to above room temperature.
-S
mag
[J/
kgּK
]
TC [
K]
100
150
200
250
300
350
0.05 0.15 0.25 0.35
Smag sol-gel samples
Smag ceramic samples
TC sol-gel samplesTC ceramic samples
1
1.5
2
2.5
3
3.5
4
La1-xAgxMnO3 system
x
Other perovskite compounds
0
2
4
6
200 240 280 320
- S
Mag[J
/kg
·K
]
T [K]
La1-xCaxMnO3-δ system,
B=1, 3 vµ 5 T
MCE demonstration device
Schematic working principle:
Gd metal plates
Pneumatic sample handling system
Keithley Microvoltmeter to record the
temperature changes using a thermo -couple
(glued in between the Gd plates)
Computer to display the
sample temperature
changes
N SMagnet Pole
Magnet Pole
Results The magnet arrangement
B(d): Induction as dependent on the clearance between the NdFeB magnet poles
d [cm]
B [
mT
]
0
200
400
600
800
1000
1200
0 1 2 3 4 5 6
Measured on the magnet pole surface
Measured in the gap in between the magnet poles
Prepared in LT Tai responsibility
with NdFe14B material
Demonstration Experimental Setup
Temperature of the sample + holder + thermocouple in the absence of the magnetic field
290
290.5
291
291.5
292
0 20 40 60 80 100Thêi gian [täa ®é tï y ý tÝnh b»ng gi©y]
Nhi
Öt ®
é cñ
a m
Éu v
µ cÆ
p nh
iÖt ®
iÖn
(K)
Temperature of the sample holder and the thermo couple during magnetisation and demagnetisation process
290
290.5
291
291.5
292
0 20 40 60 80 100
Thêi gian [täa ®é tï y ý tÝnh b»ng gi©y]
Nhi
Öt ®
é cñ
a g¸
mÉu
vµ
cÆp
nhiÖ
t ®iÖ
n [K
]
291.0
291.2
291.4
291.6
291.8
292.0
292.2
292.4
0 20 40 60 80 100
Time [arbitary reference in seconds]
Sam
ple
Tem
pera
ture
[K
]
Actual sample temperature changes during magnetisation and demagnetisation cycles
Absolute sample temperature change at room temperature (291 K) during magnetisation and demagnetisation cycles
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0 20 40 60 80 100
Time [arbitary reference in seconds]
Sam
ple
Tem
pera
ture
[K
]
Concluding remarks:•Well designed, organised and sucessfully implemented•Publications:
Total number of papers published: 42Number of papers published internationally: 16
•Education:Number of Bachelor Theses: 15Number of Master Theses: 02PhD Project proposed and started: 01
•Research continued after this project: Cryo-Lab, Solid State Department, CMS, ITIMS, IMS etc. (about 20 % of international scientific publications of the Vietnamese Physics Community in the last 8 years deal with MCE)• International Cooperation promotion: extension, lot of new relationships and programmes established
NP Thuy: •A decent and modest person, a bright and intelligent physicist with a sucessful career, featured by deep insight in every topic he approached, long term vision and sharp sense, great scientific imagination, intuitivity and creativity, always with an open mind and endless enthousiasm to catch up and to start with new topics, ideas and technologies.•A kind colleague with strong attraction and capability to link together and to encourage both students and co-workers