"Exchange-field-narrowing" process for the inhomogeneously broadened EPR lines in superconductors

Abstract

A simplified version of the theory, describing the narrowing of inhomogeneously and dipolar broadened EPR lines by the long range exchange in superconductors, is presented. This is the so-called "exchange-field-narrowing" process, in which the localized magnetic moments processing with different frequencies are coupled by the exchange molecular fields, but not by the mutual spin flips. It is also shown that a simple formula for the width of exchange narrowed EPR line can be obtained which takes into account the effects of both the exchange fields and the exchange fluctuations. © 1985