Observation of magnetic state dependent thermoelectricity in superconducting spin valves

TL;DR

This paper reports the experimental observation of magnetic state-dependent thermoelectric effects in superconducting spin valves, revealing complete magnetic control and sign inversion phenomena, with implications for sensitive radiation detection.

Contribution

It demonstrates for the first time the magnetic control over thermoelectric effects in superconducting spin valves, including sign reversal influenced by interfacial domain walls and high magnetic fields.

Findings

Thermoelectric effects depend on the magnetic state of the spin valve.

Sign of thermoelectricity can invert with magnetic configuration.

Large thermoelectric signals observed even at high magnetic fields.

Abstract

Superconductor-ferromagnet tunnel junctions demonstrate giant thermoelectric effects which are being exploited to engineer ultra-sensitive terahertz radiation detectors. Here, we experimentally observe the recently predicted complete magnetic control over thermoelectric effects in a superconducting spin valve, including the dependence of its sign on the magnetic state of the spin valve. The description of the experimental results is improved by the introduction of an interfacial domain wall in the spin filter layer interfacing the superconductor. Surprisingly, the application of high in-plane magnetic fields induces a double sign inversion of the thermoelectric effect, which exhibits large values even at applied fields twice the superconducting critical field.