Optimised GMR sensors for low and high frequencies applications

Local recording of biological magnetic fields using Giant Magneto Resistance-based micro-probes

“…We took advantage of this technology to build magnetic probes adapted to biological preparations. GMR-based sensors are highly malleable in shape, can be miniaturized at the micro-scale without sensitivity loss7, and, working at room temperature, can be placed in contact or potentially penetrate the living tissue, permitting highly local recordings both in vitro and in vivo . Simply electrically supplied with two wires, its handling is as simple as for an electrode.…”

Nanoscale dissipation and magnetoresistive1/fnoise in spin valves

“…As a rule of thumb 3 , a featureless 1/f noise spectrum results from a superposition of more than one active two-level fluctuator per octave of frequency. In our 1 kHz measurement bandwidth there must exist at least 10 fluctuators in this sub-volume to give the featureless 1/f spectrum suggesting an upper limit of 9 29 This suggests long-range spatial correlations of the noise, which are not observed (except in the collinear configuration, which is not a sensor). At the opposite extreme, a magnetic volume on the scale of the exchange length, 4 3 nm 3 , 30 is expected to behave as a single domain particle and give rise to white noise at low frequency and a noise peak at the ferromagnetic resonance frequency.…”

Very low field magnetic resonance imaging with spintronic sensors

“…The resistance of such a device varies as the angle between the reference and soft layers. Linearized GMR spin valves present a linear resistance variation with small field variation and optimized GMR sensors can reach 10 pT/ √ H z at 77 K. 10 A mixed sensor is the combination of a superconductive loop with a Giant Magneto-Resistance. 8 The superconductive loop is made of a large loop which integrates the flux on a large surface (1 cm 2 typically) and a μm size constriction where the current density is much higher.…”