Comparing XRD data for 225C and 300C growth of Si-Heusler.

Some composition assumption for sample grown at 225C.

S230 grown at 300CSi Comp = 22.9 at.%

S239 grown at 225CSi Comp = 27 at.%?

1009080706050Co Percent Metal

1.0

0.8

0.6

0.4

0.2

0.0

x10

-2

4.10

4.05

4.00

3.95

3.90

0.12

0.10

0.08

0.06

0.04

0.02

0.00

1.003

1.002

1.001

1.000

0.999

0.998

0.997

In-P

lan

e P

ositio

n

4.0

3.5

3.0

2.5

2.0

1.5

1.0

In-P

lan

e F

WH

M 1

0-2

1.0

0.8

0.6

0.4

0.2

x10

-3

2.06

2.04

2.02

2.00

1.98

1.96

1.94

5

4

3

2

1

0

x10

-4

1.03

1.02

1.01

1.00

0.99

0.98

0.97

Integrated Intensity

Peak Position [rlu]

Peak FWHM [rlu]

L(014)h=(022)c K(014)h=(022)c L(102)h=(002)c L(011)h=(111)c

Int=0.0069

1009080706050Co Percent Metal

2.5

2.0

1.5

1.0

0.5

0.0

x10

-2

4.08

4.06

4.04

4.02

4.00

3.98

3.96

3.94

3.920.12

0.10

0.08

0.06

0.04

0.02

0.00

Ou

t-o

f-P

lan

e F

WH

M

1.004

1.002

1.000

0.998

0.996

In-P

lan

e P

ositio

n

4.0

3.5

3.0

2.5

2.0

1.5

1.0

In-P

lan

e F

WH

M 1

0-2

3.0

2.5

2.0

1.5

1.0

0.5

0.0

x10

-3

2.04

2.02

2.00

1.98

1.96

1.5

1.0

0.5

0.0

x10

-4

1.02

1.01

1.00

0.99

0.98

Integrated Intensity

Peak Position [rlu]

Peak FWHM [rlu]

L(014)h=(022)c K(014)h=(022)c L(102)h=(002)c L(011)h=(111)c

Int=0.0117

Things I noticed:• (022) intensity higher for 225C growth at Heusler Comp• Large area of higher intensity and in-plane lattice matching (65-90)%Co

– FWHM shows similar trend• No Significant difference in in-plane peak width for the two growth

temperatures• (111) very wide at 225C growth• On the 300C sample, the strain is different for each reflection (the

position traces do not collapse on top of each other) wereas they agree in the 225C sample

• Comparing Zero Strain w/Si concentration suggests zero strain if Si was 25at%

• Zero Strain doesn’t necessarily correspond with highest intensity of narrowest peak

Comparing Chemical Order

3

4

5

67

0.01

2

3

4

5

67

0.1

2

3

4

Inte

nsi

ty R

atio

1009080706050Co Percent Metal

S1/F (300C) S2/F S1/F (225C) S2/F

The idea here is to measure the chemical ordering qualitatively. I’ve divided the integrated intensity of each superlattice peak by the fundamental to remove variations in structural disorder.

F=(022)c=(014)hS1=(002)c=(102)hS2=(111)c=(011)h

• No significant changes in intensity within the “good” region (65-85)% Co

• No difference in S1/F for the two temperatures

• Significant difference in intensities for S2/F: the (111) peak is MUCH stronger relative to the fundamental peak for 300C growth

Comparing phi-scan FWHM• Voigt could not fit well, so I found

FWHM via max value and located max/2 in the data after background subraction

• S239 had 2 components probably due to 2 distinct populations of grain sizes. I fit the wider as a polynomial background

• Clearly, the sample grown at 225C has a narrower width at the Heusler composition

FWHM vs Comp at Two Growth Temps

Example of two components in s239 Heusler Stoichiometry Data Compare

2

3

4

567

1

2

3

4

Ph

i-Sca

n F

WH

M [D

eg

]

1009080706050Co Percent Metal

s239 (225C) s230 (300C)

8

6

4

2

No

rmed

In

ten

sity

x 1

0-3

26.025.024.023.022.021.0Phi [Deg]

Data Fit Bkg

Voigt Fit: |X|² = 2.8973Intensity: 0.001946 ± 3.8349e-05Amplitude: 0.0059389 ± 6.5139e-05Position: 23.803 ± 0.00096075FWHM: 0.2086 ± 0.0034152Shape: 10000 ± 0

0.3

0.2

0.1

0.0

No

rmed

In

ten

sity

26.025.024.023.022.021.0Phi [Deg]

s239 (225C) s230 (300C)

L-scans of (014) on s231 (Si~19at%)Grown at 150C and 1/3 as Thick as Others

• A couple bad spots at ~90% Co• Zero strain @ ~84% Co• Position/Strain changes monotonically/linearly• Width strange

4.08

4.06

4.04

4.02

4.00

3.98

3.96

3.94

Po

sitio

n [

rlu]

1009080706050Co Percent Metal

60

55

50

45

40

35

FW

HM

[rlu 1

0-3]

6810

-4

2

4

6810

-3

2

4

68

Integ

rated In

ten

sity

Some General Conclusions• Si-concentration is a bigger factor to determine strain than Co/Mn ratio• Higher Co concentration is better ordered than Heusler stoichiometry

regardless of growth temp according to intensities• Large region of composition gives good ordering according to peak

widths• These samples are still too different to make a definitive statement on

growth temperature– Different Si concentrations– Different layer ordering when grown– Different thicknesses (at least the 150C sample)

• Improving the study:– Study Si-dependant samples– Grow all three samples in a immediately after each other rather than venting

or composition recalibration to ensure const Si btwn samples