![Die Gemäldesammlung des Johann Gottlob von Quandt ...Quandt 1860 (2), S. 73, Nr. 367: „Sehr brav in schwarzer und weisser Kreide auf braun[es] Papier gezeichnet.“ 12 Gemäss Hinweis](https://static.fdocuments.net/doc/165x107/6063fccd6047c9164a1af9f4/die-gemldesammlung-des-johann-gottlob-von-quandt-quandt-1860-2-s-73-nr.jpg)
K. Krüger 1 , C. Thede 2 , K . Seemann 1 , H. Leiste 1 , M. Stüber 1 , E. Quandt 2
1
KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association Thermal stability of the ferromagnetic in-plane uniaxial anisotropy of Fe-Co-Hf-N/Ti-N multilayer films for high-frequency sensor applications K. Krüger 1 , C. Thede 2 , K. Seemann 1 , H. Leiste 1 , M. Stüber 1 , E. Quandt 2 1 Institute for Applied Materials (IAM-AWP), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany 2 Institute for Materials Science, Kiel University, Kiel, Germany [email protected] Motivation Idea: contactless inspection of wear state of surfaces and coatings Sample preparation Two-step process: Deposition and subsequent heat treatment Ferromagnetic material Protective material Ti-N Fe-Co-Hf-N Substrate 700 W (DC) 250 W (RF) Fe 37 Co 46 Hf 17 - target 150 mm TiN-target 150 mm Si/SiO 2 (1 µm)- substrate p = 0.2 Pa Ar/N 2 atmosphere (N 2 ≈ 3 Vol.- %) turbomolecular pump 1. Reactive DC and RF magnetron sputter deposition 2. Heat treatment • Annealing for 1 h at T a = 400 °C or T a = 600 °C in a static magnetic field (50 mT) in vacuum after deposition Generation of an in-plane uniaxial anisotropy H u to ensure a homogenous precession of magnetic moments in an external high- frequency field Rotatable table: • Fe 32 Co 44 Hf 12 N 12 and Ti 50 N 50 individual layers with number of bilayers n = 7 • Individual layer thickness Fe 32 Co 44 Hf 12 N 12 : d FeCoHfN = 53 nm • Individual layer thickness Ti 50 N 50 : d TiN = 67 nm Experimental [1] T.L. Gilbert, IEEE Trans. Magn. 40 (2004) [2] K. Seemann, H. Leiste, V. Bekker, J. Magn. Magn. Mater. 278 (2004) Heater Substrate Outlook Uniaxial anisotropy field: • Temperature stability of µ 0 H u depends on a possible oxidation process of the magnetic layer Further investigations on the oxidation process at high temperatures Temperature dependent resonance frequency: • Verification of the thermal stress • Integration of the thermally induced residual stress in the model for f r (T) by introducing a magnetoelastic anisotropy • Experimental verification of f r (T) Summary • By annealing the Fe 32 Co 44 Hf 12 N 12 /Ti 50 N 50 multilayer films at either T a = 400 °C or 600 °C for 1 h in a static magnetic field in vacuum a uniaxial anisotropy field of about µ 0 H u ≈ 5 mT was induced • The films annealed at T a = 600 °C show a temperature stability of µ 0 H u up to 500 °C at least for 1 h Thermally induced strain relaxes instantaneously Fe 32 Co 44 Hf 12 N 12 / Ti 50 N 50 multilayer films annealed at T a = 600 °C for 1 h are suitable for detecting changes in the resonance frequency up to 500 °C • In contrast, the films annealed at T a = 400 °C lose this metastable state above 200 °C, because the orientation of µ 0 H u in the film plane has shifted out of its room temperature direction • The change of the uniaxial anisotropy field direction could have been caused by mechanically and thermally induced strain in the magnetostrictive material Thermally induced strain starts to relax after approximately 3 h at 500 °C Fe 32 Co 44 Hf 12 N 12 /Ti 50 N 50 multilayer films annealed at T a = 400 °C for 1 h are less suitable for detecting changes in the resonance frequency above 200 °C Temperature-dependent ferromagnetic properties • A shift in the resonance frequency f r with increasing temperature is expected due to a decrease of J s • Temperature stability of the resonance peak depends on a possible degradation of the thermally induced uniaxial anisotropy field H u at high temperatures Study: • Investigation of the thermal stability of H u thermally induced at T a = 400 °C and T a = 600 °C Temperature-dependent VSM measurements in easy and hard axis of polarization from room temperature (RT) up to 500 °C multilayer design: protective coating with an integrated sensor function Quantification of mechanical stress changes (Δσ) and temperature changes (ΔT) in the sensor material by a shift of the resonance frequency f r • Decrease of coercive field H c in the hard axis of polarization • Saturation polarization J s decreases with increasing temperature • Clear distinction between easy and hard axis up to 500 °C • Absolute value of µ 0 H u decreases slightly from 5 mT at RT to 3.4 mT at 500 °C • Uniaxial anisotropy field µ 0 H u remains stable in its direction up to 500 °C within one hour Fe 32 Co 44 Hf 12 N 12 /Ti 50 N 50 multilayer films annealed at T a = 600 °C for 1 h are suitable for detecting changes in the resonance frequency up to 500 °C Kittel resonance formula: • Decrease in J s and µ 0 H u f r decreases with increasing temperature Dynamic behavior of magnetic moments in a HF-field: Landau-Lifschitz-Gilbert equation (L-L- G) [1] in combination with the Maxwell equations to consider eddy-currents [2]: Results Multilayer films annealed for one hour at T a = 600 °C in vacuum Experiment: f r at 20 °C Prediction: f r with increasing temperature Multilayer films annealed for one hour at T a = 400 °C in vacuum • Kittel formula: a decrease in f r is predicted due to the decrease in J s (T) and µ 0 H u (T) with increasing temperature • 20 °C: f r was confirmed experimentally • Due to thermal fluctuations the damping parameter α is expected to increase • f r (T) will also be affected by α(T) • No oxygen in the multilayer film due to annealing in vacuum • TiN top layer has oxidized to a large extent to TiO 2 • A diffusion of the oxygen to the magnetic Fe 32 Co 44 Hf 12 N 12 layer has not occurred Ferromagnetic properties are maintained Temperature-dependent hysteresis loop measurements in easy and hard axis of polarization from RT up to 500 °C in air Auger electron spectroscopy depth profiles Before heating up to 500 °C: After heating up to 500 °C in air for 1 h during the measurement : Oxidation process due to heating in air? • Clear distinction between easy and hard axis at RT • Above 200 °C the clear distinction starts to vanish The direction of µ 0 H u seems to shift out of its originally preferred direction Hysteresis loop measured in the “hard axis” of polarization shows a decreasing uniaxial anisotropy field µ 0 H u Fe 32 Co 44 Hf 12 N 12 / Ti 50 N 50 multilayer films annealed at T a = 400 °C for 1 h are less suitable for detecting changes in the resonance frequency above 200 °C Temperature-dependent hysteresis loop measurements in easy and hard axis of polarization from RT up to 500 °C in air Effect of time at 500 °C on the orientation of µ 0 H u : The direction of µ 0 H u relaxes towards its originally direction at room temperature after 3 h 40 min at 500 °C h in h refl Non- contact HF-sensor µ r (f, ∆σ, ∆T) -1 0 -8 -6 -4 -2 0 2 4 6 8 10 -1 .2 -0 .8 -0 .4 0.0 0.4 0.8 1.2 Fe 32 Co 44 Hf 12 N 12 /Ti 50 N 50 # B ilayer n = 7 annealed for 1h @ 600°C to talm ag n etic layer th ickn ess d m = 370 nm P olarization, J (T ) M ag ne tic flu x de n sity,µ 0 H ext (m T) 2 0 °C 100°C 200°C 300°C 400°C 500°C easy axis -10 -8 -6 -4 -2 0 2 4 6 8 10 -1.2 -0.8 -0.4 0.0 0.4 0.8 1.2 Fe 32 Co 44 Hf 12 N 12 /Ti 50 N 50 # B ilayer n = 7 annealed for 1h @ 600°C to talm ag n etic layer th ickn ess d m = 370 nm 20°C 100°C 200°C 300°C 400°C 500°C P olarization, J (T ) M a g ne tic flux den sity, µ 0 H ext (m T) h ard axis 0 100 200 300 400 500 1.50 1.75 2.00 2.25 2.50 Prediction,according to Kittel form ula Experim ental data Resonance frequency, f r (G Hz) Temperature, T (°C) 0 20 40 60 80 100 120 0 10 20 30 40 50 60 70 80 90 100 Fe 32 Co 44 Hf 12 N 12 /Ti 50 N 50 # B ilayern = 7 annealed for1h @ 600°C in vacuum Atom ic concentration, c (%) Sputtertim e, t (min) O Ti N Fe Co Hf 0 20 40 60 80 100 0 10 20 30 40 50 60 70 80 90 100 Fe 32 Co 44 Hf 12 N 12 /Ti 50 N 50 # B ilayern = 7 annealed for1h @ 600°C in vacuum and heated for 1h @ 500°C in air Atom ic concentration, c (%) Sputtertim e, t (min) O Ti N Fe Co Hf -10 -8 -6 -4 -2 0 2 4 6 8 10 -1.2 -0.8 -0.4 0.0 0.4 0.8 1.2 Fe 32 Co 44 Hf 12 N 12 /Ti 50 N 50 # B ilaye r n = 7 annealed for 1h @ 400°C to talm ag n etic layer thickness d m = 370 nm 20°C 100°C 200°C 300°C 400°C 500°C P olarization, J (T) M a g ne tic flu x de nsity, µ 0 H ext (m T) easy axis -1 0 -8 -6 -4 -2 0 2 4 6 8 10 -1 .2 -0 .8 -0 .4 0.0 0.4 0.8 1.2 Fe 32 Co 44 Hf 12 N 12 /Ti 50 N 50 # B ilayer n = 7 annealed for 1h @ 400°C to talm ag n etic layer thickness d m = 370 nm 2 0 °C 100°C 200°C 300°C 400°C 500°C P o larization , J (T ) M a g ne tic flu x d en sity, µ 0 H ext (m T) h ard axis 1 2 3 4 5 -400 -200 0 200 400 600 = 0.037 J S = 1.15 T 0 H U = 4.2 m T = 1 .2 m Fe 32 Co 44 Hf 12 N 12 /T i 50 N 50 # B ilay er n = 7 an n ea led fo r 1h at 6 0 0°C to tal m a g n e tic lay er th ic kn ess d m = 370 nm R e(µ r ) Im (µ r ) L-L -G P erm eability, µ r Frequency, f (G Hz) 0 45 90 135 180 225 270 315 360 -0 .8 -0 .6 -0 .4 -0 .2 0.0 0.2 0.4 0.6 0.8 1.0 1h@ 5 0 0 °C 3h40min@ 5 0 0 °C 4h30min@ 5 0 0 °C 2 0 °C , fo r co m pa rison Fe 32 Co 44 Hf 12 N 12 /Ti 50 N 50 # B ilayer n = 7 annealed for 1h @ 400°C to talm ag n etic layer th ickn ess d m = 370 nm P ro je cte d re m a n e n ce p o la riza tio n, J r,x (T ) R o tation an gle , (°)
description
250 W (RF). 700 W (DC). Fe 37 Co 46 Hf 17 -target 150 mm. TiN -target 150 mm. F erromagnetic material. Protective material. h in. Si/SiO 2 (1 µm)- substrate. Non- contact HF-sensor. Fe -Co- Hf -N. Ti -N. h refl. p = 0.2 Pa Ar/N 2 atmosphere (N 2 ≈ 3 Vol.-%). - PowerPoint PPT Presentation
Transcript of K. Krüger 1 , C. Thede 2 , K . Seemann 1 , H. Leiste 1 , M. Stüber 1 , E. Quandt 2
KIT – University of the State of Baden-Wuerttemberg andNational Research Center of the Helmholtz Association
Thermal stability of the ferromagnetic in-plane uniaxial anisotropy of Fe-Co-Hf-N/Ti-N multilayer films for high-frequency sensor applications
K. Krüger1, C. Thede2 , K. Seemann1, H. Leiste1, M. Stüber1, E. Quandt2
1 Institute for Applied Materials (IAM-AWP), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany2 Institute for Materials Science, Kiel University, Kiel, Germany
Motivation
Idea: contactless inspection of wear state of surfaces and coatings
Sample preparation
Two-step process: Deposition and subsequent heat treatment
Ferromagnetic material Protective material
Ti-NFe-Co-Hf-N
Substrate
700 W (DC)250 W (RF)
Fe37Co46Hf17-target 150 mm
TiN-target 150 mm
Si/SiO2(1 µm)- substrate
p = 0.2 PaAr/N2 atmosphere
(N2 ≈ 3 Vol.-%)
turbomolecular pump
1. Reactive DC and RF magnetron sputter deposition 2. Heat treatment• Annealing for 1 h at Ta = 400 °C or Ta = 600 °C
in a static magnetic field (50 mT) in vacuum after deposition
Generation of an in-plane uniaxial anisotropy Hu to ensure a homogenous precession of magnetic moments in an external high-frequency field
Rotatable table:• Fe32Co44Hf12N12 and Ti50N50 individual layers with number of bilayers n = 7• Individual layer thickness Fe32Co44Hf12N12: dFeCoHfN = 53 nm• Individual layer thickness Ti50N50: dTiN = 67 nm
Experimental
[1] T.L. Gilbert, IEEE Trans. Magn. 40 (2004)[2] K. Seemann, H. Leiste, V. Bekker, J. Magn. Magn. Mater. 278 (2004)
Heater
Substrate
OutlookUniaxial anisotropy field:• Temperature stability of µ0Hu depends on a possible oxidation process of
the magnetic layer Further investigations on the oxidation process at high temperatures
Temperature dependent resonance frequency:• Verification of the thermal stress • Integration of the thermally induced residual stress in the model for fr(T) by
introducing a magnetoelastic anisotropy• Experimental verification of fr(T)
Summary• By annealing the Fe32Co44Hf12N12/Ti50N50 multilayer films at either Ta = 400 °C or 600 °C for 1 h in a static magnetic field in vacuum a uniaxial anisotropy field of
about µ0Hu ≈ 5 mT was induced• The films annealed at Ta = 600 °C show a temperature stability of µ0Hu up to 500 °C at least for 1 h Thermally induced strain relaxes instantaneously Fe32Co44Hf12N12 / Ti50N50 multilayer films annealed at Ta = 600 °C for 1 h are suitable for detecting changes in the resonance frequency up to 500 °C
• In contrast, the films annealed at Ta = 400 °C lose this metastable state above 200 °C, because the orientation of µ0Hu in the film plane has shifted out of its room temperature direction
• The change of the uniaxial anisotropy field direction could have been caused by mechanically and thermally induced strain in the magnetostrictive material Thermally induced strain starts to relax after approximately 3 h at 500 °C Fe32Co44Hf12N12/Ti50N50 multilayer films annealed at Ta = 400 °C for 1 h are less suitable for detecting changes in the resonance frequency above 200 °C
-10 -8 -6 -4 -2 0 2 4 6 8 10-1.2
-0.8
-0.4
0.0
0.4
0.8
1.2Fe32Co44Hf12N12/Ti50N50
# Bilayer n = 7annealed for 1h @ 600°Ctotal magnetic layerthickness dm= 370 nm
Pol
ariz
atio
n,
J (T
)
Magnetic flux density, µ0Hext (mT)
20°C 100°C 200°C 300°C 400°C 500°C
easy axis
-10 -8 -6 -4 -2 0 2 4 6 8 10-1.2
-0.8
-0.4
0.0
0.4
0.8
1.2Fe32Co44Hf12N12/Ti50N50
# Bilayer n = 7annealed for 1h @ 600°Ctotal magnetic layerthickness dm= 370 nm
20°C 100°C 200°C 300°C 400°C 500°C
Pol
ariz
atio
n,
J (T
)
Magnetic flux density, µ0Hext (mT)
hard axis
0 100 200 300 400 5001.50
1.75
2.00
2.25
2.50 Prediction, according to Kittel formula Experimental data
Res
onan
ce fr
eque
ncy,
f r (
GH
z)
Temperature, T (°C)
0 20 40 60 80 100 1200
10
20
30
40
50
60
70
80
90
100Fe32Co44Hf12N12/Ti50N50
# Bilayer n = 7annealed for 1h @ 600°C in vacuum
Ato
mic
con
cent
ratio
n,
c (%
)
Sputter time, t (min)
O Ti N Fe Co Hf
0 20 40 60 80 1000
10
20
30
40
50
60
70
80
90
100Fe32Co44Hf12N12/Ti50N50
# Bilayer n = 7annealed for 1h @ 600°C in vacuumand heated for 1h @ 500°C in air
Ato
mic
con
cent
ratio
n,
c (%
)
Sputter time, t (min)
O Ti N Fe Co Hf
-10 -8 -6 -4 -2 0 2 4 6 8 10-1.2
-0.8
-0.4
0.0
0.4
0.8
1.2Fe32Co44Hf12N12/Ti50N50
# Bilayer n = 7annealed for 1h @ 400°Ctotal magnetic layerthickness dm= 370 nm
20°C 100°C 200°C 300°C 400°C 500°C
Pol
ariz
atio
n,
J (T
)
Magnetic flux density, µ0Hext (mT)
easy axis
-10 -8 -6 -4 -2 0 2 4 6 8 10-1.2
-0.8
-0.4
0.0
0.4
0.8
1.2Fe32Co44Hf12N12/Ti50N50
# Bilayer n = 7annealed for 1h @ 400°Ctotal magnetic layerthickness dm= 370 nm
20°C 100°C 200°C 300°C 400°C 500°C
Pol
ariz
atio
n,
J (T
)
Magnetic flux density, µ0Hext (mT)
hard axis
1 2 3 4 5-400
-200
0
200
400
600
= 0.037J
S = 1.15 T
0H
U = 4.2 mT
= 1.2 m
Fe32Co44Hf12N12/Ti50N50
# Bilayer n = 7annealed for 1h at 600°Ctotal magnetic layerthickness dm= 370 nm
Re(µr)
Im(µr)
L-L-G
Per
mea
bilit
y, µ r
Frequency, f (GHz)
Temperature-dependent ferromagnetic properties
• A shift in the resonance frequency
fr with increasing temperature is expected due to a decrease of Js
• Temperature stability of the resonance peak depends on a possible degradation of the thermally induced uniaxial anisotropy field Hu at high temperatures
Study:• Investigation of the thermal
stability of Hu thermally induced at Ta = 400 °C and Ta = 600 °C
Temperature-dependent VSM measurements in easy and hard axis of polarization from room temperature (RT) up to 500 °C
multilayer design:protective coating with an integrated sensor function
Quantification of mechanical stress changes (Δσ)and temperature changes (ΔT) in the sensor material
by a shift of the resonance frequency fr
• Decrease of coercive field Hc in the hard axis of polarization• Saturation polarization Js decreases with increasing temperature• Clear distinction between easy and hard axis up to 500 °C• Absolute value of µ0Hu decreases slightly from 5 mT at RT to 3.4 mT at 500 °C• Uniaxial anisotropy field µ0Hu remains stable in its direction up to 500 °C within
one hour Fe32Co44Hf12N12/Ti50N50 multilayer films annealed at Ta = 600 °C for 1 h are suitable
for detecting changes in the resonance frequency up to 500 °C
Kittel resonance formula: • Decrease in Js and µ0Hu
fr decreases with increasing temperature
Dynamic behavior of magnetic moments in a HF-field:Landau-Lifschitz-Gilbert equation (L-L-G) [1] in combination with the Maxwell equations to consider eddy-currents [2]:
ResultsMultilayer films annealed for one hour at Ta = 600 °C in vacuum
Experiment: fr at 20 °C Prediction: fr with increasing temperature
Multilayer films annealed for one hour at Ta = 400 °C in vacuum
• Kittel formula: a decrease in fr is predicted due to the decrease in Js(T) and µ0Hu(T) with increasing temperature
• 20 °C: fr was confirmed experimentally• Due to thermal fluctuations the damping
parameter α is expected to increase• fr(T) will also be affected by α(T)
• No oxygen in the multilayer film due to annealing in vacuum
• TiN top layer has oxidized to a large extent to TiO2
• A diffusion of the oxygen to the magnetic Fe32Co44Hf12N12 layer has not occurred
Ferromagnetic properties are maintained
Temperature-dependent hysteresis loop measurements ineasy and hard axis of polarization from RT up to 500 °C in air
Auger electron spectroscopy depth profiles
Before heating up to 500 °C:
After heating up to 500 °C in airfor 1 h during the measurement :
Oxidation process due to heating in air?
• Clear distinction between easy and hard axis at RT• Above 200 °C the clear distinction starts to vanish The direction of µ0Hu seems to shift out of its originally preferred direction Hysteresis loop measured in the “hard axis” of polarization shows a
decreasing uniaxial anisotropy field µ0Hu
Fe32Co44Hf12N12 / Ti50N50 multilayer films annealed at Ta = 400 °C for 1 h are less suitable for detecting changes in the resonance frequency above 200 °C
Temperature-dependent hysteresis loop measurements ineasy and hard axis of polarization from RT up to 500 °C in air
0 45 90 135 180 225 270 315 360
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1h@500°C 3h40min@500°C 4h30min@500°C 20°C, for comparison
Fe32Co44Hf12N12/Ti50N50
# Bilayer n = 7annealed for 1h @ 400°Ctotal magnetic layerthickness dm= 370 nm
Pro
ject
ed re
man
ence
pol
ariz
atio
n, J
r,x (T
)
Rotation angle, (°)
Effect of time at 500 °C on the orientation of µ0Hu:
The direction of µ0Hu relaxes towards its originally direction at room temperature after 3 h 40 min at 500 °C
hin
hrefl
Non-contactHF-sensor
µr(f, ∆σ, ∆T)
