2. Spin Valves: - larger MR values then the AMR-based devices - exchange energy should be large (> 0.2 erg/cm -2 ) - blocking temperature > 300C - effective coupling field between the free and the pinned layer < 10-20 Oe - synthetic antiferromagnets to increase the exchange, improve the temperature dependence of the exchange field, and reduce the demagnetizing and coupling fields acting on the free layer - synthetic free layers to reduce the effective magnetic thickness and the moment of the free layer.

3. Magnetic tunnel junctions: - spin dependent tunneling across an insulating barrier: - incoherent (amorphous AlOx barrier) - coherent (crystalline MgO barrier) - incoherent scattering (Jullier’s model): - transition metal ferromagnetic electrodes – CoFe, CoFeB, Fe

4. Spin valve sensors: - controlling magnetic field during deposition (inducing magnetic anisotropy) free and pinned layer easy axis can be set parallel (MRAM) or orthogonal (linear sensors, read heads). - output voltage of unshielded sensor with orthogonal free and pinned layer -  R/R: maximum MR signal (15-20 %) - is sensor square resistance  : sample resistivity - t: sample thickness - W: width of the read element - h: sensor height - I: sensor current -  f : angle between free layer and longitudinal direction -  p : angle between pinned layer and longitudinal direction

5. Magnetic tunnel junction sensors: - higher MR ration and higher noise levels - MTJ sensor output: - can be expressed in terms of H c, H coupling and H k_eff - for read head applications, in the 100–300 Gbit/in 2 region, the junction resistance must be around 1  m 2.

6. Signal-to-noise ratio in SVs and MTJs for read head applications: - MTJ have higher MR ratio and higher noise levels - At 1 GHz in MTJ – thermal and shot noise - additional noise associated with resonant spin precession around the effective magnetic field - signal-to-noise ratio: - for MTJ, MR depends on bias voltage - for spin valve, MR not dependent on bias voltage - sensor dimensions typical of 100 Gbit in −2 applications:

7. Biomolecular recognition: A typical spintronic (or magnetoresistive) biochip consists of the following features: (i) Array of magnetoresistive sensors. (ii) Hybridization chamber. (iii) Target arraying mechanism.

8. Two concepts have to be introduced to design a magnetoresistive biochip: 1. biological sensitivity of the assay - the capability of a biomolecule in solution to recognize its complementary biomolecule immobilized to the sensor surface. 2. sensor label sensitivity - the capability for the sensor to detect a single magnetic particle. Depending on the biochip application, the type of the sensor and its area may be optimized to detect either large concentrations of particles or single particles!

9. Limits of detection: 1/f noise of spin-valve sensor: 1/f noise of MTJ sensor: N C is the number of current carriers participating in the current I  is the phenomenological Hooge parameter A is the MTJ area  H is a modified Hooge parameter The barrier material of the MTJ has no effect on the 1/f noise magnitude, the RA product of the MTJ is an important parameter! magnetic 1/f noise - fluctuations of the magnetic domains in the free and pinned layer of the sensor.

10. assuming that the MTJ and SV have the same area (and therefore the same spatial resolution), the same linear range and the same frequency of operation: