Read Back Signals in Magnetic Recording - Research Group Fidler

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6.2.5 Signal of a Perfect Transition FEM Simulations To calculate the signal of a perfect transition a track width of 120 nm, a data layer thickness of 12 nm, and a spontaneous polarization of J s = 0.44 T was assumed. The read back signal was investigated for both kind of transitions ( →← and ←→). Figure 6.9 and Figure 6.10 show the read back signal of the read head with and without shields for the different kind of transitions. The head velocity was 20 m/s. For this calculation the Gilbert damping constant was 0.3 and 1.0 for the GMR sensor and the shield respectively. The signal peaks for the full read head simulation (with shields) are more localized compared to the simulation without shields. The asymmetric transfer curve leads to a large difference in amplitude height for both cases. Again the output voltage is shifted up for the read back signal with shields due to mirror currents, as we have already seen in Figure 6.7. Output Voltage [V] 0.1070 0.1065 0.1060 0.1055 0.1050 0.1045 0.1040 -300 -200 -100 0 100 200 300 x [nm] ΔR/R [%] 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 -1.2 -1.4 -1.6 -300 -200 -100 0 100 200 300 without shields with shields x [nm] Figure 6.9: The read back signal and the relative change in resistance for a perfect →← transition. 74
Output Voltage [V] 0.1074 0.1072 0.1070 0.1068 0.1066 0.1064 0.1062 0.1060 x [nm] FEM Simulations 0.1058 -300 -200 -100 0 100 200 300 ΔR/R [%] 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 -300 -200 -100 0 100 200 300 without shields with shields x [nm] Figure 6.10: The read back signal and the relative change in resistance for a perfect ←→ transition. 6.2.6 Read Back Signal Finally the read back signal was calculated. As replacement for the data layer, a bit pattern as shown in Figure 6.11 was used. It consists of 30 bits with perfect transitions, which are alternately magnetized in positive and negative x-direction. The assumed bit length was 60 nm, which is equal to the gap of the read head model. The track width was 120 nm, which is larger than the free layer width. The thickness was 12 nm and the flying height of the head, i.e. the distance between ABS and the data layer was 10 nm. The spontaneous polarization was 0.44 T. Figure 6.12 shows the read back signal for a read head with and without shields. According to the transfer curve the output signal for the whole read head (with shields) is again shifted up, due to mirror current effects. The shields lead to an increase of the amplitude. Therefore the read back signal is much better, although the signal for single perfect transitions was lower than that without shields (see previous section). This fact can be traced back to the wider peaks in the absence of the shields, so that the signals of consecutive transitions partially cancel each other. 75
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DIPLOMARBEIT Read Back Signals in M
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Abstract This thesis concentrates o
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Contents 3.2.4 Signal of Written Bi
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Introduction 1 IntroductionEquation
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Introduction In 1955, before the RA
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2 BasicsEquation Section (Next) 2.1
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Basics curl H = 0 . (2.15) So H is
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Basics This is justified, because t
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Basics Here J ij represents the exc
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s Basics ∂J α ∂J =−γ J× He
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Basics for spin down electrons. An
Page 23 and 24: Basics Figure 2.4: Schematic model
Page 25 and 26: Basics channels in the parallel and
Page 27 and 28: Basics Nowadays there are again eff
Page 29 and 30: Analytical Calculations 3 Analytica
Page 31 and 32: Analytical Calculations developing
Page 33 and 34: Analytical Calculations t C 8 π =
Page 35 and 36: µ 0 Hsig [T] 0.030 0.025 0.020 0.0
Page 37 and 38: Analytical Calculations n n ⎛HH,
Page 39 and 40: z Analytical Calculations Figure 3.
Page 41 and 42: 4 Numerical MethodsEquation Numeric
Page 43 and 44: Numerical Methods ϕ ( x ) =δ . (4
Page 45 and 46: Numerical Methods current flowing o
Page 47 and 48: Numerical Methods ∫ ∫ ∫ si =
Page 49 and 50: Numerical Methods Figure 4.2: The l
Page 51 and 52: Numerical Methods j =−σgrad Φ.
Page 53 and 54: Numerical Methods within the volume
Page 55 and 56: Numerical Methods Integration of Am
Page 57 and 58: 4.5 Time integration Numerical Meth
Page 59 and 60: 5 Read Head DesignEquation 5.1 Bias
Page 61 and 62: Read Head Design The exchange bias
Page 63 and 64: Read Head Design free layer (see Fi
Page 65 and 66: FEM Simulations 6 FEM SimulationsEq
Page 67 and 68: FEM Simulations Magnetic Material J
Page 69 and 70: 6.2 Results FEM Simulations In the
Page 71 and 72: Output [V] 0.108 0.107 0.106 0.105
Page 73: FEM Simulations has a greater influ
Page 77 and 78: 7 OutlookEquation Section (Next) Ou
Page 79 and 80: Appendix A In case we have the func
Page 81 and 82: Appendix B Moreover the second inte
Page 83 and 84: List of Figures List of Figures Fig
Page 85 and 86: List of Figures Figure 6.1: The mag
Page 87 and 88: Bibliography [11] H. Katayama, M. H
Page 89 and 90: Bibliography [38] W. F. Brown Jr.,
Page 91: Lebenslauf Otmar Ertl Reinprechtsdo
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Read Back Signals in Magnetic Recording - Research Group Fidler

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