Cooling and heating with electron spins: Observation of the spin Peltier effect

TL;DR

This paper reports the first experimental observation of the spin Peltier effect, demonstrating heat flow driven by spin currents in a ferromagnetic structure, advancing the field of spin caloritronics and magnetic heat management.

Contribution

It introduces the spin Peltier effect, a novel spin thermoelectric phenomenon, and provides experimental measurements and modeling of the effect in a spin valve structure.

Findings

Observation of heat flow driven by spin currents.

Measurement of spin Peltier coefficients between -0.9 and -1.3 mV.

Demonstration of magnetic control of heat flow.

Abstract

The Peltier coefficient describes the amount of heat that is carried by an electrical current when it passes through a material. Connecting two materials with different Peltier coefficients causes a net heat flow towards or away from the interface, resulting in cooling or heating at the interface - the Peltier effect. Spintronics describes the transport of charge and angular momentum by making use of separate spin-up and spin-down channels. Recently, the merger of thermoelectricity with spintronics has given rise to a novel and rich research field named spin caloritronics. Here, we report the first direct experimental observation of refrigeration/heating driven by a spin current, a new spin thermoelectric effect which we call the spin Peltier effect. The heat flow is generated by the spin dependency of the Peltier coefficient inside the ferromagnetic material. We explored the effect in a specifically designed spin valve pillar structure by measuring the temperature using an electrically isolated thermocouple. The difference in heat flow between the two magnetic configurations leads to a change in temperature. With the help of 3-D finite element modeling, we extracted permalloy spin Peltier coefficients in the range of -0.9 to -1.3 mV. These results enable magnetic control of heat flow and provide new functionality for future spintronic devices.