Recent developments in (Mn,Fe)2(P,Si) materials · 2(P,Si) materials H. Yibole Fundamental Aspects...
Transcript of Recent developments in (Mn,Fe)2(P,Si) materials · 2(P,Si) materials H. Yibole Fundamental Aspects...
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Recent developments in (Mn,Fe)2(P,Si) materials
H. Yibole
Fundamental Aspects of Materials and Energy, TU Delft, The Netherlands
DDMC 2015, 2nd Nov
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OutlinePart I:
- Parameters influencing the cyclability of the MCE
in (Mn,Fe)2(P,Si,B) compounds
- Compositional mapping of magnetocaloric figure of merit
- Mechanical stability
Part II:
- Growth of single-crystalline (Mn,Fe)2(P,Si)
- Magnetocrystalline anisotropy
- Magnetic behaviour towards the ferromagnetic state
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Fe2P-based manganese compounds
Tegus et al., Nature 415, 150 (2002)
Magneto-elasticFirst-order phase transition
Hexagonal (Mn,Fe)2(P,Si) compounds
N.H. Dung et al., Adv. Energy Mater. 1, 1215 (2011)
∆B = 2 T∆B = 1 T
∆B = 5 T∆B = 2 T
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Cyclability of the MCE
- Thermal hysteresis
- Finite transition width
- Shift of the transition due to the field
....
cyclic= measured
Irreversible
...
∆Tad
t
“Initial” state
Cyclability is a complex question !
Real FOMT
B =0
B =Bt
∆Tad
S
T
dTtr/dB
280 290 300 310 3200.0
0.5
1.0
1.5
2.0
2.5
T cycl
ic (K
)
T (K)
B = 1.1 T
Mn1.25Fe0.70P0.50Si0.50
H. Yibole et al., J. Phys. D: Appl. Phys. 47, 075002(2014)
Direct ∆T method
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30 40 50 60 70
277
278
279
280+B +B+B+B+B +B
-B-B-B
T (K
)
t (s)
-B -B
Boron doped (Mn,Fe)2(P,Si) materials
F. Guillou et al., Adv. Mater., 26, 2671 (2014)
- Mn/Fe = 1, optimization of saturation MPromising MCE properties
50 100 150 200 250 3000
20
40
60
80
100
120
140
160
M
(A m
2 kg-1
)
T (K)
1 T
MnFe0.95P2/3-xSi1/3Bx
x = 0x = 0.075
Other promising compositions in this system?
- Metalloid site, controlling the phase transition
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Influence of B content on hysteresis and sensitivity of transition to field
MnFe0.95P0.67-xSi0.33Bx
x = 0.070
x = 0.065
x = 0.060
x = 0, but Si=0.45
0
20
40
60
80
100
120
M (A
m2 k
g-1)
(c)
250 260 270 280 2900
20
40
60
80
100
120
M (A
m2 k
g-1)
T (K)
(d)
0
20
40
60
80
100
120
M (A
m2 k
g-1)
(b)0
20
40
60
80
100
120
M (A
m2 k
g-1)
(a)
0.05 T
1 T
dTtr/dB = 4.2 K/TdTtr/dB (1T) > hysteresis
dTtr/dB = 4.1 K/TdTtr/dB (1T) > hysteresis
dTtr/dB = 3.6 K/TdTtr/dB (1T) ≈ hysteresis
dTtr/dB = 2.1 K/TdTtr/dB (1T) < hysteresis
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Magnetocaloric effect in B ~1 T
∆S from Indirect method,MB(T) using Maxwell equation
∆Tcyclic from direct measurement
- dTtr/dB (1T) > hysteresis, ∆Tcyclic is ensured
- dTtr/dB (1T) ≈ hysteresis, ∆Tcyclic is reduced
- dTtr/dB (1T) < hysteresis, ∆Tcyclic disappears
250 260 270 280 290
-20
-16
-12
-8
-4
0
T (K)
Cool. ; Heat. ; B0.07
; B0.065
; B0.06
; Si0.45
S
(J k
g-1 K
-1)
250 260 270 280 2900.0
0.5
1.0
1.5
2.0
2.5
T cy
clic(K
)
T (K)
Sweeping modeB = 1.1 T
B = 1 T
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Threshold hysteresis for MCE cyclability
Direct method ∆Tcyclic = 1.1 K
Indirect method ∆Tad = 2.65 K
- Distinction between ∆Tad and ∆Tcyclic
for materials with hysteresis.
- dTtr/dB (1T) ≈ hysteresis:
threshold for MCE cyclability.
- In (Mn,Fe)2(P,Si,B ), dTtr/dB ≈ 4.2 K the
maximal hysteresis ≤ 4 K for B ~1 T.
MnFe0.95P0.61Si0.33B0.06
40 50 60 70 80
263
264
265
-B
T
(K)
t (s)
+B (b)
B = 1T
260 265 270 275
-70
-60
-50
-40
-30
-20
-10
B = 0 Cool. ; Heat.
B = 1 T Cool. ; Heat.
[S-S
(280
K)]
(J k
g-1 K
-1)
T (K)
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Mapping of magnetocaloric figure of merit
Coefficient of refrigerant performance (CRP) (Wood and Potter 1985)
Type of ∆T CRP
MnFe0.95P0.595Si0.33B0.075
∆Tad 0.62
∆Tcyclic 0.62
MnFe0.95P0.61Si0.33B0.060
∆Tad 0.78
∆Tcyclic 0.37
Gd ∆T 0.17
0,8 0,9 1,0 1,1 1,20,00
0,05
0,10
0,15
B
Mn
0
0,10
0,21
0,31
0,41
0,52
0,62
CRPcyclic(1 T)(a)
0,8 0,9 1,0 1,1 1,20,25
0,30
0,35
0,40
0,45
Si
Mn
(b)
max
0
( , ) 'B
C
refrigerant capacity S TCRPpositive work on refrigerant
M T B dB
Si = 1/3
B = 0.07(hysteresis < 1 K)
(hysteresis = 3.5 K)
150 < T < 380 K.
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Mechanical stability of (Mn,Fe)2(P,Si,B)
- Sample A: MnFe0.95P0.582B0.078Si0.34 (boron doped)
- Sample B: Mn1.25Fe0.7P0.5Si0.5 (Mn-rich)
- Sample C: MnFe0.95P0.55Si0.45 (Mn/Fe = 1)
-150 -100 -50 0 50 100 150 200 250-2
-1
0
1
2
3
4
5
6
[(c/a
)-(c/
a)T C
] / (c
/a) T C
(%
)
T-TC (K)
A B C
(c)
0 5 10 15 20
255
260
265
270
275
T C (K
)
(b)
0 5 10 15 20210
220
230
240
250
260
270
280
290
T C (K
)
n (cycle)
0 5 10 15 20 25
264
268
272
276
280
284
288
T C (K
)
TC Heating TC Cooling
(a)A
B
C
The degradation of material may result from:
- The volumetric stress resulting from volume change
- Anisotropic internal stress
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0 5 10 15 20 25 301E-6
1E-5
1E-4
1E-3
0,01
0,1
1
0 5 10 150
20406080
100120140
(1
0-6
m)
n (cycle)
(
m)
n (cycle)
T = 340 K
Mechanical stability
200 220 240 260 280 300 320 3400
4
8
12
16
20
24
28
32
36
(1
0-6
m)
T (K)
200 220 240 260 280 300 320 3400
50
100
150
200
250
300
350
400
450
500
(1
0-6
m)
T (K)
(b)
(a)
200 220 240 260 280 300 320 340
0
2
4
6
8
10
12
14
T (K)
(1
0-3
m)
(c)
(A)
(B)
(C)
Electrical resistivity measurement
- Sample A: MnFe0.95P0.582B0.078Si0.34 (boron doped)
- Sample B: Mn1.25Fe0.7P0.5Si0.5 (Mn-rich)
- Sample C: MnFe0.95P0.55Si0.45 (Mn/Fe = 1)
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Mechanical stability
- MnFe0.95P0.585Si0.34B0.075
~ no ∆V, small ∆(c/a)
- Mn1.25Fe0.7P0.5Si0.5
limited ∆V, small ∆(c/a)
- MnFe0.95P0.55Si0.45
limited ∆V, large ∆(c/a)0 1 2 3 4 5 6 18 19 20 210
200
400
600
800
HV
n (cycle)
Vickers micro-hardness measurements
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Part I:
− Definition of a thermal hysteresis threshold ensuring the cyclic character of the MCE in the
MnFe(P,Si,B) system
− Compositional mapping of the magnetocaloric performances : identification of MnFe(P,Si,B)
compositions with promising performances on a broad temperature range 150 < T < 380 K.
− Quantification of mechanical ageing due to cycling across the transition by DSC, resistivity
micro-hardness. The mechanical degradation is highly dependent on the (c/a) change.
Conclusions
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Part II: Single-crystalline (Mn,Fe)2(P,Si)
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(Mn,Fe)2(P,Si) Single Crystals
- Anisotropy
Needs for single crystals:
- Homogeneity
- Absence of grain boundaries
Viktor Hoglin, PhD Thesis, Uppsala Universitet.
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- Growth technique: Flux method
- Metallic flux: tin
- Crystal habit: prismatic
- Crystal surface: regular and homogeneous
- Average dimension: ~ 0.15×0.15×1.5 mm3
- Colour: metallic
(Mn,Fe)2(P,Si) Single Crystals
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Single crystal diffraction and refinement
- Chemical composition (EDS): Mn0.83Fe1.17P0.72Si0.28
- Crystal structure: Hexagonal Fe2P
- Space group: 62
- Refinement method: full-matrix least-squares on F2
Reciprocal-Space mapping
Bruker AXS Kappa APEX II DiffractometerAtomic position: 3g (x1, 0, 1/2); 3f (x2, 0, 0); 2c (1/3, 2/3, 0); 1b (0, 0, 1/2)
hk0 hk1
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0 100 200 3000
20
40
60
80
100
120
0 50 100 150 200 250 3000
20
40
60
80
100
120
M (A
m2 /k
g)
T (K)
Virgin curve
c // H
H = 1 T
M (A
m2 /k
g)
T (K)
FC FW
Magnetic properties of ferromagnetic crystal
Chemical composition: Mn0.83Fe1.17P0.72Si0.28
First-order ferromagnetic transition !
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0.0 0.5 1.0 1.5 2.00
20
40
60
80
100
120
140
160
180
c0H
c // 0H
After two cycles
M (A
m2 /k
g)
0H (T)
T = 5 K
Mangetocrystalline anisotropy in Mn0.83Fe1.17P0.72Si0.28 crystal
Corrected demagnetization field
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0.0 0.5 1.0 1.5 2.00
1
2
3
H
int/( 0M
)
(M)2 (T2)
sin sin
Sucksmith-Thompson plot
0.28 10 /
0.22 10 /
The preferred magnetization direction --- along the c axis !
Mangetocrystalline anisotropy energy for hexagonal system
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Mangetocrystalline anisotropy of related polycrystalline compounds
L. Caron et al, PRB 88, 094440 (2013)
Fe2P single crystalNeutron powder diffraction
- Fe-rich Mn0.66Fe1.29P1−xSix (x = 0.42, 0.37,0.34)
angle with c-axis 67˚, 46˚, 29˚Ou et al, J. Mag. Magn. Mater. 340, 80 (2013)
- MnFeP0.5As0.5along c-axisBacmann et al, J. Mag. Magn. Mater. 134, 59 (1994)
- Mn-rich Mn1.3Fe0.64P0.5Si0.5 and Mn1.1Fe0.9P0.8Ge0.2(a,b) planeDung et al, PRB 86, 045134 (2012); Liu et al, PRB 79, 014435 (2009);
0.28 10 /
0.22 10 /
2.3 10 /Fe2P
Mn0.83Fe1.17P0.72Si0.28
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0 1 2 3 4 50
30
60
90
120
150
180
0 1 2 3 4 50
30
60
90
120
150
180
M (A
m2 /k
g)
0H (T)
c // 0H
T = 5 K T = 5 K
M (A
m2 /k
g)
0H (T)
c 0H
Peculiar magnetic behaviour towards ferromagnetic state
(After ZFC)
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0 1 2 3 4 50
30
60
90
120
150
180
M (A
m2 /k
g)
0H (T)
T = 5 K 0 100 200 300 400 500 600 700
156
158
160
162
164
166
M (A
m2 /k
g)
t (s)
B = 2.6 T
c // µ0H
Spontaneous magnetization jumps
- Phase transition behaviour- Not magnetic screening by eddy currents or domain wall movements
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Possible interpretations for magnetization jumps
(i) An underlying antiferromagnetic order
G. Li et al, Appl. Phys. Lett. 105, 262405 (2014).
- Prompted by chemical disorder on 3f and 3g site
(ii) A dynamical phase separation phenomenon
- General to a First-order phase transition (Manganites, Gd5Ge4, Heusler alloys, CeFe2, FeRh,etc.)
(iii) A combination of both
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Conclusions
Part II:
− (Mn,Fe)2(P,Si) single crystals presenting FOMT have been grown for the first time.
− Crystal structure and magnetic properties support the findings of previous works on polycrystals.
− The weakening of the magnetocrystalline anisotropy from Fe2P to Mn0.83Fe1.17P0.72Si0.28
is beneficial for magnetocaloric application.
− The magnetization process toward the ferromagnetic state turns out to be complex.
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Acknowledgements
Dr. YingKai Huang,Van der Waals-Zeeman Institute
Dr. Graeme R. Blake,Zernike Institute for Advanced Materials
Dr. Francois GuillouDr. Giacomo PorcariDr. Lian ZhangDr. Niels van DijkProf. Dr. Ekkes Brück
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More details:
H. Yibole et al., Appl. Phys. Lett. 107, 162403 (2015).
F. Guillou et al., Adv. Mater. 26, 2671 (2014).
H. Yibole et al., J. Phys. D: Appl. Phys. 47 075002 (2014).
F. Guillou et al., J. Appl. Phys. 116, 063903 (2014).
F. Guillou et al., J. Alloys & Compd. 617, 569 (2014).
F. Guillou et al., Phys. status solidi (c) 11, 1007 (2014).
F. Guillou et al., J. Alloys & Compd. 632, 717 (2015).
Thank you for your attention!