Magneto-chemical studies with a new ultrasensitive superconducting quantum magnetometer

A magnetometer utilizing quantum superconductivity as the basis for the flux sensor element has been designed and used for biochemical susceptibility measurements in the temperature range from 1.5°K to 300°K. The sensitivity and reproducibility of this instrument have been tested by measurements on small amounts of material of well-known susceptibilities. Using this instrument the temperature dependence of the magnetic susceptibilities of oxy- and metaquohemerythrin have been measured and for the first time their anti-ferromagnetic components have been unambigiously resolved. From this data the exchange coupling constants between the two high-spin iron (III) atoms in each subunit have been determined to be -77 and -134 cm^(-1) respectively.