From Local Moment EPR in Superconductors to Nanoscale Ferromagnets

Abstract

Electron paramagnetic resonance (EPR) in metals has contributed a lot to the understanding of the electronic structure and magnetic properties in dilute alloys as well as in concentrated ferromagnets. We recall some pioneering work of the Kazan group and others, studying local moment EPR in superconductors. An SNS Josephson junction has been used as a microwave generator and as an EPR detector at once. EPR was also used to study the Kondo effect in the EPR g-shift and linewidth. Moreover, the high sensitivity of EPR (down to 1010 spins) allows to study single atomic layers of ferromagnets below and above the Curie temperature T C as well as the spin fluctuations at T C. The in situ ferromagnetic resonance (FMR) in ultrahigh vacuum (UHV) offers a unique possibility to study the interlayer exchange coupling (IEC) and spin dynamics of coupled ferromagnetic films. Furthermore, the magnetic resonance enables us to measure basic parameters of nanoscale magnets in absolute energy units (i.e., μeV/spin). The current status of the UHV-FMR in nanoscale ferromagnets will be discussed.