Large-scale simulation of L10 FePt nanoparticle toward magnetic recording
Hung Ba Tran,1,2,* , Yu-Ichiro Matsushita1,2,3
1Tokyo Institute of Technology, Japan.

E-mail: tran.h.ag@m.titech.ac.jp

2Quemix Inc., Tokyo, Japan.
3QST, Tokyo, Japan.

Introduction

PurposeTo develope large-scale simulation for L10 FePt nanoparticle
toward magnetic recording applications.

Methods

timemsMicromagneticsimulations

µs
Monte
Carlo

DFT

Kohn-Sham Heisenberg
equationsmodel

Energy barrier for magnetic flips of L10 FePt nanoparticle is important factorfor magnetic recording applications [1-4]Results and Discussions

Micromagneticns

LandauLifshitzGilbertequationMonte Carlosimulations

psDFTfsnm

pm

µmmm

lengthSize effect on Curie temperature of L10 FePt nanoparticles

First-principles calculations for L10 FePt bulk

Cutoff of exchangeinteractions

43FePtFe pdos
2.0 Pt pdos
0.0

1 dash: susceptibility

2solid: magnetization

001234Distance d/a

5Fe: 2.951 𝝁𝐁 /𝐚𝐭𝐨𝐦
Pt: 0.329 𝝁𝐁 /𝐚𝐭𝐨𝐦

64.0-100-50ENERGY(eV)

0200

1.5

L=103621220.50000.51x (nm)1101.5y (nm)

4y (nm)y (nm)

21

120

12Theory
Fit(Theory)
Exp.
Bulk
203040D (nm)300800

01000

1050

L=2002x (nm)462m (µΒ/atom)

L=570!𝟏/𝝂

Magnetization layer-resolved of L10 FePt nanoparticles
𝒎 (𝝁𝐁 /𝐚𝐭𝐨𝐦)

PtFe

400
600
T (Κ)

5

Magnetization profile of L10 FePt nanoparticles@300 K

𝑻𝐂 ∞ − 𝑻𝐂 (𝑫)
𝑫
=𝑻𝐂 ∞
𝑫𝟎

40

2.0

−2−4

2

100

TC(D)/TC(bulk) (%)

6

L=5L=10
L=20
L=40
Bulk

χ (a.u)8DOS(/eV)

10Jij (meV)4.0Fe−Fe pairs
Fe−Pt pairs
Pt−Pt pairsm (µB/f.u)

12MAE(Bulk-DFT) 14.4 MJ/m3MAE(Thin film-EXP.) 4-11 MJ/m3

L= 5
L= 10
L= 20
L= 40
L= 80
L=160
L= ∞

@300 K

10x (nm)001020x (nm)

30

4050

DEnergy barrier of magnetic flips of L10 FePt nanoparticles

3221

Hys[001]
Hys[100]
M⌧H[001]M⌧H[100]

0−150 K
0H (Τ)

25−255033221

Hys[001]
Hys[100]
M⌧H[001]M⌧H[100]

0−10H (Τ)

251×10650

Hys[001]
Hys[100]
M⌧H[001]M⌧H[100]

0−10.01

Dcritical(This work): 3.7 nm
Dcritical(Exp.): 4.0 nm

1−2−2200 K−30H (Τ)

25300 K−350−250H (Τ)

25

L=10
L=11
L=12
L=13
L=14
L=15
L=16
L=20
L=24
L=28
L=32
L=36
L=40
L=60
L=80

100
11

L=2
L=3
L=4
L=5
L=6
L=7
L=8
L=910000

100 K−3M (µB/f.u)

M (µB/f.u)

0−2−3−25

Hys[001]
Hys[100]
M⌧H[001]M⌧H[100]−1−2−2511×108K×V (meV)

3M (µB/f.u)

M (µB/f.u)

Hysteresis loop and M-H curves of L10 FePt nanoparticles

50Conclusions
Developement of large-scale simulation of L10 FePt nanoparticle for magnetic
recording
The experimental results of resistivity and Curie temperature are well
reproduced by our methodology
The L10 FePt nanoparticles, which have diameter less than 3.7 nm, can notstore data more than 10 years

𝑲×𝑽 ≈ 𝟔𝟎𝒌𝐁 𝑻 (10 years)

10L=120L=160
60kBTT (K)100

RT1000

Empirical rule base on Arrhenius-Neeĺ equation𝜏 = 𝜏" 𝑒!"#$ %(𝜏" ≅ 10#$ − 10#%" second)

Papers of this study[1] H. B. Tran, H. Momida, Y. Matsushita, K. Sato, Y. Makino, K. Shirai, T. Oguchi,Phys. Rev. B 105, 134402 (2022).
[2] H. B. Tran, H. Momida, Y. Matsushita, K. Shirai, T. Oguchi, Acta Mater. 231,117851 (2022).
[3] H. B. Tran, Y. Matsushita, Appl. Mater. Today 32, 101825 (2023).
[4] H. B. Tran, Y. Matsushita, “Temperature and size dependence of energy barrier formagnetic flips in L10 FePt nanoparticles: First-principles study”, DOI:
10.2139/ssrn.4462256 (2023)