This document summarizes the development of an Fe-Cu-Nb-Si-B based nanostructure alloy for soft magnetic properties. It describes how annealing the alloy at different temperatures and times affects properties like grain size, permeability, coercivity, and losses. The key findings are that annealing at 545°C for 30 minutes produces a maximum initial permeability of 23,065 along with low coercivity below 1 A/m, low losses between 17.752-26.234 W/kG, and remanence between 2.183-3.224 kG, demonstrating the alloy's suitability for soft magnetic applications.

1. Development of Fe-Cu-Nb-Si-B
Based Nanostructure
for Soft Magnetic Properties
Presented by
Md. Khalid Hossain
Scientific Officer
Institute of Electronics
Atomic Energy Research Establishment
Bangladesh Atomic Energy Commission , Dhaka-1349
June 24, 2013
1

2. Lecture Outline
2
1. Fe-Based Soft Nanocomposite Magnetic Materials
2. Theoritical basis for magnetic softening
3. Importance of Nano-crystalline Alloys
4. Review of the Work on Nano-crystalline Alloy
5. Experimental
6. Result And Discussion
7. Conclusion

3. Fe-Based Soft Nanocomposite Magnetic Materials
An excellent soft magnetic property in nanocrystalline
alloys based on Fe-Cu-Nb-Si-B commercially known as
FINEMET was first discovered in 1988.
The major requirements for superior soft magnetic
properties are :
 high initial permeability
 extremely low coercivity
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4. Theoritical basis for magnetic softening
Soft magnetic properties on the basis of Random Anisotropy Model
(RAM). According to this model, D = L / 3 .
Where, D= Grain ize
L= Exchange correlation length.
4
For bcc Fe-(20%Si) , L = 35 nm.
So, grain size D becomes 10 – 15 nm.
Therefore, grain size must be lies 10-15 nm for
Fe73.5Cu1Nb3Si13.5B9 nanocrystalline alloy.
Finemet has a low coercivity (Hc < 1 A/m) and high initial
permeability (µi ≈ 105).

5. Importance of Nano-crystalline Alloys
Nano-crystalline alloys play an important role in the
modern technology for it’s soft magnetic properties, i.e.
 high saturation magnetization
 high permeability
 good frequency behavior
 low losses
 good thermal stability
 reduction in size and
 low weight
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6. 6
So nano-crystalline alloys are smart candidate in
telecommunication system.
Its also important in power transformer core where
high saturation induction and low hysteresis losses
are of principle importance.

7. Review of the Work on Nano-crystalline Alloy
The original alloy composition is Fe73.5 Cu1 Nb3.5 Si13.5 B9 .
 Cu helps the nucleation of -Fe(Si)
 Nb controls grain growth
 Si and B has been used as glass forming materials.
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8. Experimental
 Amorphous ribbon of Fe73.5Cu1Nb3Si13.5B9 alloys
was prepared by melt- spinning method
 Amorphousity, crystallization temperature, grain
size and composition of the grains were
determined by X-ray diffraction (XRD).
 Annealing was performed in Muffle Furnace
 Complex permeability was measured by an
Impedance Analyzer
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9. From these X-ray spectra we observe that the crystallization
starts in the temperature 500-525°C, while at Ta = 700°C
very sharp peak (110) is obtained with large grain size. This
peaks are indexed as bcc Fe-Si phase.
Result And Discussion
9

10. The Lattice parameter of the bcc Fe-Si phase decreases with
increasing annealing temperature Ta up to 545°C and then the value
of lattice parameter increases up to annealing temperature 680°C.
2.82
2.83
2.84
2.85
2.86
2.87
450 500 550 600 650 700
Annealing temperature, Ta (° C)
Latticeparameter,(Å)
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11. % of Si with the increase of annealing temperatures and time
have the reverse effect in comparison with the effect of lattice
parameter
0
5
10
15
20
25
450 500 550 600 650 700
Annealing temperature, Ta (° C)
Silicon(at%)
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12. At 490°C the grain size is smaller in size, 7nm, and with the
increase of annealing temperature grain size is getting bigger
in size within the range of (823) nm.
0
5
10
15
20
25
450 500 550 600 650 700
Annealing temperature, Ta (° C)
Grainsize,Dg(nm)
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13. The initial permiability ( µ’ ) increases with anneling temperature upto 490°C then
decreases suddenly. Again initial permiability ( µ’ ) increases sharply passing
through a maxima at 545°C and then dramatically falls to very low value.
f = 1 kHz
0
5000
10000
15000
20000
25000
0 100 200 300 400 500 600 700
Ta (°C)
µ'
0
0.0005
0.001
0.0015
0.002
0.0025
0.003
0.0035
0.004
0.0045
tanδ/µ'
initial permiability ( µ' )
relative loss factor ( tan δ/ µ' )
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14. Permeability increases with annealing time attaining a maximum value at
30 min and than slightly decreases with longer annealing time possibly
due to induced anisotropy that develops due to longer holding time
Ta = 545 °C
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000
22000
24000
26000
1 10 100 1000 10000
f (kHz)
µ'
5 min
10 min
30 min
35 min
40 min
45 min
60 min
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15. Loss Factor
ta = 30 min
0
0.5
1
1.5
2
2.5
3
300 350 400 450 500 550 600 650
Ta (°C)
LossFactor,D
2 kHz
3 kHz
4 kHz
5 kHz
50 kHz
Loss factor rapidly decreases with increasing annealing temperature
for various applied frequency (2-50) kHz. Loss factor has high value
at 50 KHz and decreases with the decrease of frequency.
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16. Relative Quality Factor
For the sample annealed at 545°C for 30 minute give the maximum
quality factor if the applied frequency is lower i.e 10 kHz .
ta = 30 min
0
10000
20000
30000
40000
50000
60000
70000
300 350 400 450 500 550 600 650
Ta (°C)
RelativeQualityfactor,µ'/D
1 kHz
2 kHz
3 kHz
5 kHz
10 kHz
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17. Magnetic Hysterisisgraph
ta = 30 min
-8
-6
-4
-2
0
2
4
6
8
-12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12
H (Oe)
B(kG)
Field dependence BH Loop of Fe73.5Cu1Nb3Si13.5B9
alloy which is annealed at 545°C for 30 minute. 17

18. Coercivity (Hc)
Ta = 545°C
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 10 20 30 40 50 60 70
Time (min)
Coercivity,Hc(Oe)
The coercivity is decreased if the annealing time is increased. But
in all the case the coercivity remain low (0.616 -0.406) oersted
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19. Core losses
The core losses remain low (26.234 -17.752) W/kG if the
annealing time is in the range of 1 minute to 60 minute
Ta = 545°C
0
5
10
15
20
25
30
0 10 20 30 40 50 60 70
Time (min)
Loss(W/kG)
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20. Remanence
The remanence is decreased if the annealing time is increased.
But in all the case the remanence remain low (3.224 -2.183) kG.
Ta = 545°C
0
0.5
1
1.5
2
2.5
3
3.5
0 10 20 30 40 50 60 70
Time (min)
Remanence,Br(kG)
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21. CONCLUSIONS
► X-ray diffraction results show that the grain size has
been obtained in the range of 7 nm to 21 nm at different
stage of annealing and Si content has been reached
upto 21.1 at %.
► When the alloy has been annealed for 30 minutes at
various temperatures, the maximum initial permeability
(μ') was observed at 545 0C.
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22. ► For the annealing temperature of 545 0C best soft magnetic
properties has been achieved which corresponds to a
maximum value of initial permeability (μ') is 23,065 while the
corresponding value of relative loss factor is 4.002×10-5 at
fixed frequency f = 1 kHz.
► From Magnetic Hysterisisgraph is shown that, the Core
Loss is low (26.234 -17.752) W/kG, the remanence is low
(3.224 -2.183) kG and the Coercivity (Hc) is low (0.616 -0.406)
oersted, which is nothing but the good property of soft
magnetic materials.
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