Presenter: Paul Neves

Mentors: Nicholas Butch & Juscelino Leão

NIST Center for Neutron Research

Summer Undergraduate Research Fellowship
2

Outline

• Magnetic Behavior of Cu2OSeO3 (Background)

• Sample Synthesis/Characterization

• SANS Measurements

• Conclusions/Future Work
3

Magnetic Structures

Higgins, Jeremy M. et al. Signature of Helimagnetic Ordering in 

Single-Crystal MnSi Nanowires. Nano Letters 10, 1605-1610 (2010)

Helical 

Structure

Ferromagnetic

Structure
4

An Interesting Material: Cu2OSeO3

Janson, O. et al. The quantum nature of skyrmions and half-skyrmions in 

Cu2OSeO3. Nature Communications 5, (2014)

Higgins, Jeremy M. et al. Signature of Helimagnetic Ordering in 

Single-Crystal MnSi Nanowires. Nano Letters 10, 1605-1610 (2010)
5

An Interesting Material: Cu2OSeO3

Seki, S. et al. Observation of Skyrmions in a 

Multiferroic Material. Science 336, 198-201 (2012)

(10 Oe = 1 mT)
6

Magnetic Skyrmions

• Topological structure

• Potential data storage 

applications

• Robust (stable)

• Result from competing 

interactions

• Limited field and 

temperature range

Kézsmárki, I. et al. Neel-type Skyrmion Lattice with Confined 

Orientation in the Polar Magnetic Semiconductor 

GaV4S8. Nature Materials 14, 1116-1122 (2015)

Yu, X. Z. et al. Real-space observation of a two-dimensional 

skyrmion crystal. Nature 465, 901-904 (2010)
7

What Are We Studying?

• Chemical substitution 

affects the skyrmion phase

• Substitute Zn for Cu

• Magnetization only

• Structure not directly 

confirmed

Wu, H. C. et al. Unexpected Observation of Splitting of Skyrmion 

Phase in Zn Doped Cu2OSeO3. Science Reports 5, (2015)

(10 Oe = 1 mT)
8

Growing Powders

• Mix/grind CuO and SeO2

• Seal in evacuated quartz 

tube

• Bake at 600°C

• Press into pellet

• Lather, rinse repeat

CuO SeO2
9

DC Susceptibility: Zn Doping

Wu, H. C. et al. Unexpected Observation of Splitting of Skyrmion 

Phase in Zn Doped Cu2OSeO3. Science Reports 5, (2015)

(10 Oe = 1 mT)
10

Small Angle Neutron Scattering

• Powders

• Cu2OSeO3

• (Cu0.9Zn0.1)2OSeO3

• ~0-70 mT Field

• On axis

• Transverse axis

• 12-53 K

https://www.ncnr.nist.gov/programs/sans/index.html

B

2θθ
11

Structural Scattering 

0.000 0.005 0.010 0.015 0.020 0.025

1

10

100

1000

10000

Zero Field Cooling, Above TC, NG7 SANS Circ. Cut

I (1/cm)

Q (1/A)

B
12

0.000 0.005 0.010 0.015 0.020 0.025

0

5

10

15

20

25

30

 Subtracted Data

I (1/cm)

Q (1/A)

0.000 0.005 0.010 0.015 0.020 0.025

1

10

100

1000

10000 Above TC

 Below TC

Zero Field Cooling, NG7 SANS Circ. Cut

I (1/cm)

Q (1/A)

SANS: Zn Doped, H On Axis

~65nm

?

?

Higgins, Jeremy M. et al. Signature of Helimagnetic Ordering in 

Single-Crystal MnSi Nanowires. Nano Letters 10, 1605-1610 

(2010)

Kézsmárki, I. et al. Neel-type Skyrmion Lattice with Confined 

Orientation in the Polar Magnetic Semiconductor 

GaV4S8. Nature Materials 14, 1116-1122 (2015)
13

SANS: Zn Doped, H On Axis
14

Future: Single Crystals?!?!
15

Summary

• Interesting results

• Expanded phase diagram

• Possible co-existence of skyrmion and helical phases 

near published phase boundaries

• Published phase diagram is too discrete

• Ongoing work
Acknowledgements

• Nick Butch, Juscelino Leão

• NIST and the SURF program

• The NCNR and CHRNS

• Julie Borchers and Joe Dura

• Dan Neumann

• Dustin Gilbert, Jeffrey Krzywon, Tanya Dax, Kefeng

Wang, I-Lin Liu, Shanta Saha, Mary Ann FitzGerald

• Doug Johnson, Patrick Connelly, Scott Slifer, Colin 

Wrenn, Andrew Malone
17

An Interesting Material: Cu2OSeO3

Janson, O. et al. The quantum 

nature of skyrmions and halfskyrmions in Cu2OSeO3. Nature 

Communications 5, (2014)

Seki, S. et al. Observation of Skyrmions in a 

Multiferroic Material. Science 336, 198-201 

(2012)
18

X-Ray Powder Diffraction

Meas. data:Cu2OSeO3-Sample1-Bake3

Intensity (cps)

 0e+000

 1e+005

 2e+005

 3e+005

 4e+005

 5e+005

2-theta (deg)

20 40 60 80
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Magnetization: Parent

Seki, S. et al. Observation of Skyrmions in a Multiferroic Material. Science 336, 198-201 (2012)
20

Magnetization: Zn Doped

Wu, H. C. et al. Unexpected Observation of Splitting of Skyrmion 

Phase in Zn Doped Cu2OSeO3. Science Reports 5, (2015)
Structural Scattering 

qq =

2ππ

dd
22

SANS: Zn Doped, H On Axis
23

SANS: Zn Doped, Transverse H

0 50 100 150 200 250 300 350

20

40

60

80

100

I (1/cm)

Phi (Degrees)

Annular Plot, (Cu0.9Zn0.1)2OSeO3, Transverse 690 Oe Field

B
24

SANS: Zn Doped, H On Axis
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SANS: Parent, H On Axis, Rotated

Without rotation

With rotation

Adams, T. et al. Long-Wavelength Helimagnetic 

Order and Skyrmion Lattice Phase in Cu2OSeO3. 

Physical Review Letters 108, (2012)
26

Future: Single Crystals?!?!