Giant demagnetization effects induced by superconducting films

TL;DR

This paper demonstrates that superconducting films can induce a giant demagnetization effect on an adjacent ferromagnetic slab, significantly altering its magnetic properties and potentially explaining recent experimental observations.

Contribution

It reveals a strong, switchable demagnetization effect caused by superconducting films on ferromagnetic layers, contrasting with previous bilayer studies.

Findings

Transition of S films from normal to superconducting state can change demagnetization factor from 0 to 1.

The effect is robust against decreasing superconducting film thickness.

Potential explanation for large ferromagnetic resonance frequency shifts in S/F/S structures.

Abstract

We show that a ferromagnetic (F) slab with the in-plane magnetization sandwiched between two superconducting (S) films experiences strong demagnetization effect due to the Meissner screening of the stray magnetic field by the superconductors. In the extreme case the transition of the S films from normal to the superconducting state can switch the demagnetization factor from 0 to 1 which is in a sharp contrast with the S/F bilayers where such transition affects the magnetic field inside the F film only slightly. The giant demagnetization effect is shown to be qualitatively robust against the decreasing of the superconducting film thickness and may provide a hint towards the explanation of the anomalously large ferromagnetic resonance frequency shift recently observed for the S/F/S structures [I. A. Golovchanskiy, N. N. Abramov, V. S. Stolyarov, V. I. Chichkov, M. Silaev, I. V. Shchetinin, A. A. Golubov, V. V. Ryazanov, A. V. Ustinov, and M. Yu. Kuprianov, Phys. Rev. Appl. 14, 024086 (2020)].