Pyromagnetic study of the magnetic phase transition in CoS2-xSex

The pyromagnetic response has been measured for the CoS
2-x
Se
x
family over a selenium concentration
x
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
x = 0.1
, 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
x = 0.1
.