New Method for Measuring the Static Magnetic Susceptibility by Paramagnetic Resonance

Abstract

This paper shows that large magnetic losses in a sample broaden the paramagnetic line in EPR without changing its g value. The expressions are derived for this ``extra line width'' for two experimental cases: (1) the oscillator frequency is stabilized to an external reference cavity; (2) the oscillator frequency is stabilized to the sample cavity. The ``extra line width'' is shown to be a simple monotonic function of the static magnetic susceptibility χ0, the Larmor frequency, the filling factor and the loaded Q of the cavity. From this, χ0 can be determined. The theory is compared with experiments on Cu(HCOO)2·4H2O and good agreement is obtained. The magnetic susceptibility of Cu(HCOO)2·4H2O is measured as a function of temperature by this technique. A weak broad maximum is observed around 70°K, in agreement with the results obtained by the usual methods.