Low frequency 1/f noise in deep submicrometer-sized magnetic tunnel junctions

Abstract

Magnetic tunnel junctions (MTJs) have been identified as promising candidates for the development of high-performance, ultra-low field magnetometers due to their high sensitivity, low cost, low power consumption, and small size. However, 1/f noise is often quite large at low frequencies and inevitably becomes one of the most difficult issues in developing a magnetic field sensor with ultrahigh sensitivity. Low-frequency 1/f noise can have both electric and magnetic origins, and it is a result of complex non-linear interactions between many degrees of freedom inside a sensor. Therefore, a reduction of the 1/f noise can be expected for the magnetic sensor with very small dimensions. Here, the dependence of the 1/f noise on voltage and strong hard-axis bias field in deep submicrometer-sized MgO-based MTJs is investigated with various junction sizes. The noise spectra were measured by using a home-built low-frequency noise measurement setup with maximum frequency up to 30 kHz. We find that the noise spectral power density is 1/f-like at low frequencies. The experimental results suggest a relative reduction of 1/f noise with respect to the intrinsic thermal noise in small-sized MTJs. The results may open a new approach for reducing the 1/f noise level in MTJ nanosensors.

[Retracted] Potential Fault Diagnosis Method and Classification Accuracy Detection of IGBT Device Based on Improved Single Hidden Layer Feedforward Neural Network

“…Compared with the single hidden layer feedforward neural network, this random generation method reduces the training parameters, improves the learning speed, and strengthens the generalization ability. It has many advantages [14][15][16][17][18].…”

Highly Sensitive Detection of Weak Low Frequency Magnetic Fields Using Single Nanoscale Orthogonal MgO Magnetic Tunnel Junctions under a Large Bias Field

“…To characterize the low-frequency noise of the MTJs, noise spectra were measured in the low-frequency range of up to 30 kHz using the home-built measurement setup, including two independent amplifier channels, which has been described in the previous work. 43) Noise measurements at different bias voltages and hard-axis bias fields (perpendicular to the film plane) were performed. The power spectrum density (PSD) S V of noise was calculated by a fast Fourier transformation of a cross correlation function of the two channels and averaged for 20 times.…”

“…Such MgO-based magnetic tunnel junctions (MTJs) are also highlighted as the most competitive sensors for ultra-low field detection due to their high sensitivity, low power consumption, and small size. [40][41][42][43] For use as magnetic-based biosensors, the detection of a weak magnetic field of superparamagnetic NPs (³nT) as biomedical magnetic tags at RT is required. 1,2) However, superparamagnetic NPs can be magnetized and detected in the presence of a relatively large external magnetic field in which other low field sensors or flux concentrators cannot be used since those are saturated in the larger working bias field.…”

“…Compared to in-plane or perpendicular MTJs, this type of orthogonal MTJ provides higher sensitivity and wider sensing range. [43][44][45][46] Our purposes are to investigate and identify the possibility of the detection of superparamagnetic NPs for use as biomarkers, and to explore the technical limit of the detection of single superparamagnetic NPs using MTJ sensors. The first major issue is the size of MTJs.…”

“…Our previous study had reported that nano-sized MTJ-based sensors provide excellent detectivity due to the reduced magnetic 1/f noise thanks to the reduction of the inhomogeneous magnetic fluctuations. 43) The second critical issue in detecting super-paramagnetic NPs using MTJ sensors is related to the large bias magnetic field that is necessary to magnetize the NPs. The large bias field may easily saturate the magnetization of a free layer with weak in-plane magnetic anisotropy.…”