Comparison of Sensitivity and Low-Frequency Noise Contributions in Giant-Magnetoresistive and Tunneling-Magnetoresistive Spin-Valve Sensors with a Vortex-State Free Layer

Abstract

Magnetoresistive spin valve sensors based on the giant-(GMR) and tunnelling-(TMR) magnetoresisitve effect with a flux-closed vortex state free layer design are compared by means of sensitivity and low frequency noise. The vortex state free layer enables high saturation fields with negligible hysteresis, making it attractive for applications with a high dynamic range. The measured GMR devices comprise lower pink noise and better linearity in resistance but are less sensitive to external magnetic fields than TMR sensors. The results show a comparable detectivity at low frequencies and a better performance of the TMR minimum detectable field at frequencies in the white noise limit.

Micromagnetic Simulations of Submicron Vortex Structures for the Detection of Superparamagnetic Labels

“…For this purpose, a connection of ten elements in series was assumed. Comparing this approximation with the results of [ 11 ] shows that S v increases by a factor 4. The square root of the S v 2 integration yields to a noise amplitude of u ≈ 104 nV, compared to an electric potential for the no label setup of u ≈ 27.4 mV, and a response just below 1 mV, which indicates an acceptable relation between the noise and the response of the simulated sensor structure.…”

“…As reported in [ 10 ], the phase noise vanishes by the use of magnetic vortex structures. Therefore, only the thermal noise and the 1/f-noise contribute to the total noise of the GMR element [ 11 ]. Since the detection of a biomolecule is an application in the low frequency range, the influence of the 1/f noise becomes dominant, and the noise increases for small sensors [ 50 ].…”

“…Since the detection of a biomolecule is an application in the low frequency range, the influence of the 1/f noise becomes dominant, and the noise increases for small sensors [ 50 ]. For an estimate of the sensor noise in our case, the model reported in [ 11 ] can be consulted. Assuming a linear decay for the normalized Hooge parameter with an increasing aspect ratio of the free layer [ 11 ], the noise parameter S v can be approximated to S v ≈ 22 nV/√Hz using a frequency of f = 10 Hz.…”

“…For an estimate of the sensor noise in our case, the model reported in [ 11 ] can be consulted. Assuming a linear decay for the normalized Hooge parameter with an increasing aspect ratio of the free layer [ 11 ], the noise parameter S v can be approximated to S v ≈ 22 nV/√Hz using a frequency of f = 10 Hz. For this purpose, a connection of ten elements in series was assumed.…”

Two-dimensional arrays of vertically packed spin-valves with picoTesla sensitivity at room temperature

“…To push the detectivity further into pT range, thus becoming competitive with magnetic tunnel junctions 26 or hybrid magnetic-MEMS devices 27 , different solutions were introduced. Large area arrays 28 , 29 and their combination with magnetic flux guides 26 have successfully delivered improved performances, at the expense of lower spatial resolution. Given the maturity of stack engineering for spin-valve multilayered thin films 24 , 30 , new design strategies are necessary to meet the demands in detection limits.…”