Critical challenges for picoTesla magnetic-tunnel-junction sensors

Low frequency 1/f barrier noise has been investigated in sputtered MgO magnetic tunnel junctions (MTJs) with a tunneling magnetoresistance ratio of up to 330% at room temperature. The lowest normalized noise parameter α of the tunnel barrier reaches 2.5 × 10−12–2.1 × 10−11 μm2, which is comparable to that found in MTJs with the MgO barrier grown by MBE or electron–beam evaporation. This normalized barrier noise is almost bias independent in the voltage range of up to ±1.2 V. The low noise level and high voltage stability may reflect the high quality of the sputtered MgO with a uniform distribution of defects in the MgO layer.

Section: Resultsmentioning

confidence: 99%

“…8,9 The 1/f noise in the P state mainly reflects the spinindependent resistance fluctuations in the tunneling barrier, 10 which are usually due to localized charge traps. [10][11][12] The barrier noise sets the minimum noise level in any type of MTJ device.…”

Section: Introductionmentioning

confidence: 99%

Very low 1/f barrier noise in sputtered MgO magnetic tunnel junctions with high tunneling magnetoresistance

Feng

Chen

Coey

2012

“…2,3 In small sensors, such as magnetoresistive sensors, this is done by using movable flux concentrators on microelectromechanical systems (MEMS) structures to modulate the magnetic field at the position of the sensor. The field modulation increases the operating frequency of the sensor to tens of kHz.…”

Section: Introductionmentioning

confidence: 99%

Enhancing the sensitivity of magnetoelectric sensors by increasing the operating frequency

Petrie

Viehland

Gray

et al. 2011

Articles you may be interested inEnhanced sensitivity in magnetoelectric current-sensing devices with frequency up-conversion mechanism by modulating the magnetostrictive strain J. Appl. Phys. 115, 17E505 (2014) We present a field modulation technique that increases the operating frequency of magnetoelectric (ME) sensors so that it can match the mechanical resonance frequency of the sensor. This not only improves the sensitivity but also reduces the effect of 1/f noise that is inherent at low frequencies. The technique, which is shown to apply to both symmetric and asymmetric ME sensors, relies on the strong, nonlinear magnetic field dependence of the magnetostriction. The combination of a lower 1/f noise and enhanced response at resonance has increased the signal to noise ratio of a symmetric sensor by two orders of magnitude. The detection limit of this sensor was lowered from 90 to 7 pT/ ffiffiffiffiffi ffi Hz p at 1 Hz in a magnetically unshielded environment.

“…Magnetic tunnel junctions (MTJs) are currently used for information readout in disk drives [1], and for high sensitivity magnetic field sensors [2], and could be used in future technologies such as spin random access memory [3]. For all these applications, the noise generated at the MTJs is a crucial factor limiting their ultimate performance.…”

Section: Introductionmentioning

confidence: 99%

Low frequency noise characteristics of submicron magnetic tunnel junctions

Zhong

Chen

Garzon

et al. 2011

We report that low frequency (up to 200 kHz) noise spectra of magnetic tunnel junctions with areas 10 −10 cm 2 at 10 Kelvin deviate significantly from the typical 1/f behavior found in large area junctions at room temperature. In most cases, a Lorentzian-like shape with characteristic time between 0.1 and 10 ms is observed, which indicates only a small number of fluctuators contribute to the measured noise. By investigating the dependence of noise on both the magnitude and orientation of an applied magnetic field, we find that magnetization fluctuations in both free and reference layers are the main sources of noise in these devices. At small fields, where the noise from the free layer is dominant, a linear relation between the measured noise and angular magnetoresistance susceptibility can be established.