Read Back Signals in Magnetic Recording - Research Group Fidler

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FEM Simulations If the current flows in the more favorable direction the exchange bias field is weakened (see Section 5.1.5), which can also be seen in Figure 6.4, when considering the torsion of the magnetization of the pinned layer. 6.2.2 Transfer Curve To get the transfer curve of the spin valve, a triangle pulsed external field as shown in Figure 6.5 is applied. Its amplitude is 0.1 T and its period time is 8 ns. As we will see later in Section 6.2.4, the changing of the external field is slow enough, so that the GMR sensor is always near equilibrium. H z [T] 0.15 0.10 0.05 0.00 -0.05 -0.10 -0.15 0 2 4 6 8 10 Time [ns] Figure 6.5: The external applied field, which is applied in z-direction to evaluate the transfer curve of the GMR sensor. 70
Output [V] 0.108 0.107 0.106 0.105 0.104 0.103 0.102 0.101 -0.10 -0.05 0.00 0.05 0.10 H z [T] FEM Simulations ΔR/R [%] Current in pos. y-direction Current in neg. y-direction Current in pos. y-direction, Hex = 0.1T 1 0 -1 -2 -3 -4 -0.10 -0.05 0.00 0.05 0.10 Hz [T] Figure 6.6: The output voltage (left) and the relative change in resistance (right, in respect to the equilibrium state) over the external applied field in z-direction for both current direction and a larger exchange bias field. The corresponding outputs for both current directions and a stronger exchange bias are given in Figure 6.8. A positive external field leads to a parallel alignment of the magnetizations of both layers, resulting in a low resistance. If the external field is applied in negative z- direction, the resistance increases, because the magnetic configuration approaches the antiparallel state. However, if the magnetic field overcomes the exchange bias field, the pinned layer magnetization is not fixed anymore and rotates towards negative z-direction. So for large negative external fields we have again a parallel state and therefore low resistance. As expected the favorable current direction shows less asymmetry in change of resistance around the equilibrium state than the opposite current direction. Moreover the GMR sensor is more sensitive, because the slope of the transfer curve at zero field is larger. The output voltage for this case is also higher, because here the magnetization vectors are more likely aligned antiparallel (see equilibrium state in Figure 6.4), leading to larger resistance. In case of a stronger exchange bias field, H ex = 0.1T , we have a much better transfer curve for higher external fields. (Unfortunately such high exchange fields are rather unrealistic. To increase the bias field for the pinned layer, synthetic antiferromagnets, as described in Section 71
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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
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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
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 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: 6.2 Results FEM Simulations In the
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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