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(a) Three-dimensional schematics of a yoke-shaped TMR sensor design and (b) an optical microscope image shows a real device with two top contacts.
(a) Typical TMR curves after the first anneal at and the second anneal at for a yoke-shaped TMR sensor. The inset of (a) shows an enlargement of the transverse TMR curves. (b) The normalized noise and TMR plotted as a function of magnetic field for a yoke-shaped TMR sensor. The inset of (b) shows the 1/f noise power spectral density as a function of frequency in the P (80 mT) and AP (−20 mT) states after subtracting the thermal and amplifier noise. Scan rates are ∼ for (a) and ∼ for (b).
Magnetic noise parameter plotted as a function of field sensitivity for different magnetic structures. All data shown are for free (open symbols) and pinned layers (solid symbols) in our normal bottom-pinned MgO MTJs annealed at (the MTJ stacks are the same as the yoke-shaped MTJ sensors) ( ), double-pinned MgO MTJs (The stack: Ta 5/Ru 30/Ta 5/NiFe 5/IrMn 10/CoFe 2.5/Ru 0.9/CoFeB 3/MgO 2/CoFeB 3/Ru 0.3/IrMn 6/NiFe 5/Ta 5/Ru 5 (units in nm)) are annealed by two steps with the first step at and the second step at ) (º ), yoke-shaped MTJs ( ), and yoke-shaped GMR spin valves in the as-grown state (The stack: Ta 5/NiFe 3/CoFe 5/Cu 2.8/CoFe 5/IrMn 10/Ta 5 (units in nm)) ( ). The dashed lines with slope 1 are guides to the eye.
(a) Typical field detectivity as a function of frequency for a yoke-shaped TMR sensor and a double-pinned TMR sensor (the device is a circular pillar with diameter of 4 μm); (b) The typical field detectivity map of a yoke-shaped TMR sensor (in units ) plotted as a function of field sensitivity and magnetic field.
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