Read Back Signals in Magnetic Recording - Research Group Fidler

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Read Head Design Figure 5.2: A comparison (left) of a conventional spin valve and a spin valve using a synthetic ferromagnet to fix the pinned layer [20]. The interlayer exchange constant (right) for two Ni80Co20 layers as function of the Ru spacer layer thickness [32]. The IEC effect has its origin in quantum interference of electron states [36]. The exchange coupling constant J IEC [J/m 2 ] depends on the nonmagnetic layer thickness t NM like ⎛ tNM ⎞ sin ⎜2π +Φ Λ ⎟ J = J ⎝ ⎠ (5.4) IEC 0 2 tNM as shown in Figure 5.2. Λ , Φ , and J 0 are constants, depending on the composition of the layers. The advantage of spin-valves with a synthetic antiferromagnetic pinned layer is the very large exchange field of IEC up to 0.5 T. This is an increase of a factor 10 compared to the direct exchange coupling with an antiferromagnet. So the stability against external fields is much better due to the higher anisotropy. Moreover the demagnetizing fields of the two ferromagnetic layers Fp,1 and Fp,2 cancel each other partially, which leads to a reduced influence on the free layer. 5.1.5 Sense Current The sense current flowing through the GMR sensor generates a magnetic field. This field also influences the pinned layer magnetization. For conventional simple spin valves there is one current direction which is more favorable. The main part of the current flows through the Cu layer, due to its higher conductivity compared to the other layers. So the current field either adds up with the demagnetizing field of the pinned layer or weakens the field acting on the 62
Read Head Design free layer (see Figure 5.3). Unfortunately the more favorable current direction causes a decline of the exchange bias field. Figure 5.3: The effect of the sense current direction on the free layer (FL). For the first case (left) the current field Hcurr partially cancels the stray field HS of the pinned layer (PL) and weakens the exchange bias field Hexch. For the other current direction (right) the stray field and the exchange bias field are supported by the current field. Shield µ → ∞ Hcurr I HS FL Cu PL Hexch Hcurr I I I Hmirr FL Cu PL Shield µ → ∞ Figure 5.4: The layers of the GMR element also see mirror currents due to the high permeability of the shields. The field of these mirror currents is able to reduce the field of the original current at the free layer and the pinned layer. Hcurr Hcurr FL Cu PL Hmirr I HS Hexch 63
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DIPLOMARBEIT Read Back Signals in M
Page 3 and 4:
Abstract This thesis concentrates o
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Contents 3.2.4 Signal of Written Bi
Page 7 and 8:
Introduction 1 IntroductionEquation
Page 9 and 10:
Introduction In 1955, before the RA
Page 11 and 12: 2 BasicsEquation Section (Next) 2.1
Page 13 and 14: Basics curl H = 0 . (2.15) So H is
Page 15 and 16: Basics This is justified, because t
Page 17 and 18: Basics Here J ij represents the exc
Page 19 and 20: s Basics ∂J α ∂J =−γ J× He
Page 21 and 22: 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: Read Head Design The exchange bias
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 and 74: FEM Simulations has a greater influ
Page 75 and 76: Output Voltage [V] 0.1074 0.1072 0.
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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