Magnetocaloric Effect and Magnetoresistance Due to Itinerant Electron Metamagnetic Transition in ${\rm Co}({\rm S}_{1-x}{\rm Se}_{x})_{2}$

The Co(S
_1-x
Se
_x
)
₂
compounds with the cubic Pyrite structure show itinerant electron metamagnetism for 0.12 ≤ x. We studied the magnetocaloric effect and magnetoresistance (MR) of this system. It was found that a substantial magnetic entropy change was obtained for Co(S
_0.88
Se
_0.12
)
₂
, which has a paramagnetic ground state. We observed giant positive MR associated with the itinerant electron metamagnetic transition for Co(S
_1-x
Se
_x
)
₂
. The magnitude of the MR jump is independent of temperature and concentration for 0.13 ≤ x ≤ 0.15. These results are discussed in terms of a simple band structure of CoS
₂
, in which high-spin polarization is realized in a ferromagnetic state.