  The absorptive and dispersive components of the frequency-dependent magnetic
susceptibility both contribute to the electron-spin resonance (ESR)
radio-frequency (rf) power absorption of local magnetic moments in metals
according to Dyson's theory. The magnetic-field prefactor present in the
expression for this power absorption has been omitted in the past when fitting
Dyson's lineshape to the observed field derivative of broad ESR rf power
absorption spectra but is shown here to significantly influence such fits and
therefore also the quantitative physical interpretations of the
temperature-dependent fit parameters.
