Low frequency noise characteristics of sub-micron magnetic tunnel junctions

TL;DR

This study investigates low frequency noise in sub-micron magnetic tunnel junctions at low temperatures, revealing Lorentzian noise spectra and magnetization fluctuations as primary noise sources, differing from larger, room-temperature junctions.

Contribution

It provides new insights into the noise characteristics of small-area, low-temperature magnetic tunnel junctions, highlighting the role of magnetization fluctuations and non-1/f noise behavior.

Findings

Noise spectra deviate from 1/f behavior at low temperatures.

Lorentzian-like noise indicates few fluctuators with ms timescales.

Magnetization fluctuations are identified as main noise sources.

Abstract

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.