Magnetometer Based On Spin Wave Interferometer

TL;DR

This paper introduces a spin wave interferometer-based magnetic field sensor that leverages phase shifts in spin waves for high sensitivity detection, demonstrating over 40 dB/Oe voltage change and a pi-phase shift within 1 Oe.

Contribution

The paper presents a novel spin wave interferometer design for magnetic sensing, achieving high sensitivity and phase shift detection at room temperature.

Findings

Voltage change exceeds 40 dB per 1 Oe near destructive interference.

The output phase exhibits a pi-phase shift within 1 Oe.

Sensor sensitivity can surpass attotesla levels due to low thermal noise.

Abstract

We describe magnetic field sensor based on spin wave interferometer. Its sensing element consists of a magnetic cross junction with four micro-antennas fabricated at the edges. Two of these antennas are used for spin wave excitation and two others antennas are used for the detection of the inductive voltage produced by the interfering spin waves. Two waves propagating in the orthogonal arms of the cross may accumulate significantly different phase shifts depending on the magnitude and the direction of the external magnetic field. This phenomenon is utilized for magnetic field sensing. The sensitivity has maximum at the destructive interference condition, where a small change of the external magnetic field results in a drastic increase of the inductive voltage as well as the change of the output phase. We report experimental data obtained on a micrometer scale Y3Fe2(FeO4)3 cross structure. The change of the inductive voltage near the destructive interference point exceeds 40 dB per 1 Oe. At the same time, the phase of the output exhibit a {\pi}-phase shift within 1 Oe. The data are collected for three different orientations of the sensor in magnetic field at room temperature. Taking into account low thermal noise in ferrite structures, the maximum sensitivity of spin wave magnetometer may exceed atta Tesla. Other appealing advantages include compactness, fast data acquisition and wide temperature operating range. The physical limits of spin wave interferometers are also discussed.