Electrical detection in two-terminal perpendicularly magnetized devices via geometric anomalous Nernst effect

TL;DR

This paper demonstrates how geometric engineering of device structures can induce a geometric anomalous Nernst effect in perpendicularly magnetized devices, enabling electrical read/write operations for high-density magnetic memories.

Contribution

It introduces a method to generate and detect the geometric anomalous Nernst effect using structural design, facilitating electrical control of magnetization in two-terminal devices.

Findings

Achieved a temperature gradient of up to 0.3 K/μm.

Demonstrated a GANE signal of 28.3 μV.

Enabled electrical write/read operations in a simple two-terminal device.

Abstract

The non-uniform current distribution arisen from either current crowding effect or hot spot effect provides a method to tailor the interaction between thermal gradient and electron transport in magnetically ordered systems. Here we apply the device structural engineering to realize an in-plane inhomogeneous temperature distribution within the conduction channel, and the resulting geometric anomalous Nernst effect (GANE) gives rise to a non-zero 2nd -harmonic resistance whose polarity corresponds to the out-of-plane magnetization of Co/Pt multi-layer thin film, and its amplitude is linearly proportional to the applied current. By optimizing the aspect ratio of convex-shaped device, the effective temperature gradient can reach up to 0.3 K/$\mu$m along the y-direction, leading to a GANE signal of 28.3 $\mu$V. Moreover, we demonstrate electrical write and read operations in the perpendicularly-magnetized Co/Pt-based spin-orbit torque device with a simple two-terminal structure. Our results unveil a new pathway to utilize thermoelectric effects for constructing high-density magnetic memories