Depth Dependence of 

Skyrmions in Thin Films

Lizabeth Quigley

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What are Skyrmions?

❏ Topologically protected magnetic 

whirlpools

❏ Difficult to destroy or deform

❏ Easy to move with electric currents

❏ Thin films are best for electronics

❏ Fit within existing devices

❏ Mostly surface interface

Need to discover difference between the 

surfaces and middle of thin film skyrmions I. Kézsmárki, Nature Materials (2015)

2
Skyrmion Differences 

❏ Thin film depth 

profile is still 

unknown

❏ Top and bottom 

differ from 

middle

Side view

Top down 

view

3

Blue → arrows pointing left 

Red → arrows pointing right
Reflectometry

❏ Intensity Falloff → Roughness

❏ Critical Edge → Where neutrons go through the sample

❏ Thickness Fringe → Thicknesses

❏ Fringe Height → Layer contrast

❏ ↑↑ ↓↓Splitting → Magnetization along field

❏ ↑↓ ↓↑ Spin Flip → Magnetization perpendicular to field

❏ Scattering Length Density (SLD) → scattering power of 

material based off of density and nuclear scattering length

https://w3auth.nist.gov/ncnr/understanding-pnr-data-features

Michael Demkowicz and Jaroslaw Majewski, Metals (2016)

4

nλ=2d*sin(Θ)

Peak → constructive λf1and λf2

Valley → destructive λf1and λf2

d
Polarized Neutron Reflectometry (PNR)

5

❏ Saturated magnetization

❏ Fit with Refl1D

❏ Fit scattering length 

densities (SLDs), 

thicknesses, 

interfaces, and 

percentage iron

❏ Developed parameters to 

be used in later fits and 

models

❏ Final fit goes with what we 

know about skyrmions

❏ Gives depth profile
❏ Magnetization was out of plane

❏ Neutrons hit in plane magnetization of skyrmions

❏ Only magnetic SLD was fit

❏ GdFe was split into three sections to allow for 

differing magnetization

❏ Many possible solutions

Skyrmion State Reflectometry

6
Object Oriented MicroMagnetic Framework (OOMMF)

Goals:

How different parameters 

affect the model

Build model of thin film

7
Varying Exchange Energy

e-11 e-11 e-11

8

Anisotropy = 200e3 J/m^3

Magnetization = 3.52 A/m

How much the magnetization wants to point in 

the same direction

Top Middle Bottom
Varying Anisotropy

9

Exchange Energy = 0.70e-11 J/m

Magnetization = 3.52e5 A/m

How much one magnetization wants to point in 

a direction, not depending on the surroundings

Top Middle Bottom
Small Angle Neutron Scattering (SANS)

10
Grazing Incidence Small Angle Neutron Scattering

(GISANS)

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Specular Scattering

Beam passing through

sample

Specular - reflecting 

off sample at the 

same angle that it 

came in with

Off Specular -

reflecting at a 

different angle then 

what it came in with

Off-specular Scattering
Simulating GISANS Data

12Intensity (arb. units)

Q (Å-1)
Simulating GISANS data

13

Intensity (arb. units)

Intensity (arb. units)

Qz (Å-1) Qy (Å-1)

Simulated GISANS Location
Simulating GISANS data

14

Intensity (arb. units)

Intensity(arb. units)

Qz (Å-1) Qy (Å-1)

Simulated GISANS Location
Simulating GISANS data

15

Intensity (arb. units)

Intensity (arb. units)

Qz (Å-1) Qy (Å-1)

Simulated GISANS Location
Simulating GISANS data

16

Intensity (arb. units)

Intensity (arb. units)

Qz (Å-1) Qy (Å-1)

Simulated GISANS Location
Future Work:

❏ Compare simulate GISANS 

data with actual data

❏ Make the two data sets equal

❏ Add neutron absorption by Gd 

to the code

❏ NIST

❏ NCNR

❏ CHRNS

❏ Dr. Alex Grutter

❏ Dr. Dustin Gilbert

❏ Dr. Brian Maranville

Thanks to:

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