Tailoring Spin Dynamic Properties of Sputtered
NiFe Thin Films with Different Seed Layers
Deepika Jhajhria*, Nilamani Behera, D K Pandya, Sujeet Chaudhary
Thin Film Laboratory, Indian Institute of Technology Delhi, New Delhi 110016
Corresponding author’s e-mail: deepika.jhajhria@gmail.com, Tel.: +91-7503733805; Fax: +91-11-26581114
*
1400
Resonance Field (Oe)
Abstract
We studied the tailoring of magnetization dynamics in
10 nm thick NiFe thin film with different seed layers (Ta,
Cu, Ru). Damping can be effectively tuned by choice of
seed layer, while the static magnetic properties remain
relatively constant. Smallest FMR line width was obtained
for Ta seed layer implying it is suitable for NiFe based spin
current devices.
1200
NiFe
1000
Ta/NiFe
Cu/NiFe
800
Ru/NiFe
600
400
200
(a)
0
2
3
4
5
6
7
8
9
10
11
Introduction
The magnetization dynamics of soft magnetic thin
films have been a subject of recent interest for its
applications in high frequency and spin current based
devices and it is often desirable to tailor the damping
behavior of magnetic relaxation. In this regard we used
different seed layers (Ta, Cu, Ru) for tuning the
magnetization relaxation and Gilbert damping in NiFe
thin films.
Experimental
NiFe films were deposited on seeded Si (100) substrate
in presence of magnetic field of 600 Oe at room
temperature by dc magnetron sputtering. The thickness
of NiFe film was kept at 10nm and that of seed layer at
5nm. Ferromagnetic resonance (FMR) signal was
recorded in 3 - 10 GHz range using a vector network
analyzer (VNA) and employing a coplanar waveguide.
Static magnetic measurements were done using MOKE
(Magneto-Optic Kerr Effect) experimental setup.
Structural and surface morphology studies have been
carried out using X-ray diffraction (XRD) and Atomic
force microscopy (AFM) respectively.
28
26
24
22
20
18
16
14
12
10
8
6
4
NiFe
Damping Constant ()
Keywords: Magnetization dynamics, seed layer, damping,
FMR line width, spin current.
FMR linewidth (Oe)
Frequency(GHz)
Ta/NiFe
Cu/NiFe
Ru/NiFe
(b)
2
3
4
5
6
7
8
9
Frequency (GHz)
10
11
0.007
0.006
0.005
0.004
0.003
(c)
0.002
NiFe
Ta/NiFe
Cu/NiFe
Ru/NiFe
Seed Layers
Fig. 1: (a) Frequency dependence of resonance fields,
(b) FMR line width ΔH as a function of frequency,
(c) Damping constant for different seed layers
As seen from Fig. 1c the damping constant α was least
at 0.0028 for sample with Ta seed layer and highest at
0.007 for Ru seed layer. However, α (~0.0045) is
comparable for single layered NiFe thin film and the
one with Cu seed layer. Correlation of interface
roughness and microstructure with the damping constant
will be presented at the conference.
Conclusions
Magnetic relaxation in NiFe thin films can be tuned in
wide range using different seed layers via different
interfacial effects and microstructure. Ta seed layer
results in lowest line width and may benefit various spin
current based magnetic devices.
References
Results
Fitting of frequency dependence of resonance field H res
data (Fig. 1a) using Kittel equation showed that
effective magnetization does not change much with
different seed layers. The intrinsic Gilbert damping
constant α was determined from the FMR line width ΔH
(Fig. 1b) using the relation of H  2   H 0
 3
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