Application of pyromagnetic phenomena to radiation detection

Using gadolinium and manganese germanide crystals we have previously demonstrated the feasibility of fast broad-band pyromagnetic detectors utilizing the critical transition of their spontaneous magnetization. In the present study we have carried out a formal thermodynamic analysis of other reversible quasi-static pyromagnetic phenomena in an attempt to discover new detection mechanisms. The formal result was applied to the case of a uniaxial ferromagnet and the results compared with experiments on gadolinium single crystals. The pyromagnetic response associated with a transition of the hard axis component of the magnetization is in good qualitative agreement with the theory. We also predict a significant increase in the response of the easy axis component with a field applied along the hard axis, but this has not yet been observed. We have made initial measurements of the pyromagnetic response at the Meissner transition of superconducting lead and tantalum. Their pyromagnetic response peaks near the critical point and has a field dependence consistent with their demagnetizing factors. The latter are at present limiting the responsivities to a few volts/watt.