The pyromagnetic response has been measured for the CoS
2-xSe
xfamily over a selenium concentration

varying from 0 to 0.15. As the concentration is initially increased from 0, the pyromagnetic peak increases in height and narrows, which is consistant with a sharpening of the second-order transition. Near

, the response suddenly drops in magnitude by a factor of 15 or so and continues to become narrower. This pyromagnetic behavior appears to be consistant with the onset of thermal hysteresis and a first-order transition near

.