MAGNETIC PROPERTIES OF COBALT AND NICKEL DICHALCOGENIDE COMPOUNDS WITH PYRITE STRUCTURE

The magnetic properties of dichalcogenide compounds, CoS2, CoSe2, NiS2, NiSe2 and the system Co(SxSe1- x)2, were studied by means of magnetic measurement, neutron diffraction and NMR. The exchange interaction Jsw of the ferromagnetic CoS2 (Tc=124°K, θp=220°K, peff =1.76µB, n=0.84µB and Hi =52kOe) was estimated to be 24cm-1 per Copair from the analysis of spin wave theory. While, CoSe2 (TN=90°K, θp=-160°K and peff=1.72µB) showed an antiferromagnetic spin ordering with MnSe2 type. NiS2 (θp =-740°K and peff=2.48µB) had no magnetic ordering even at 4.2°K. NiSe2 exhibited weak constant paramagnetism with metallic conductivity. In Co(SxSe1- x)2, (0≤x≤1), the magnetic properties and the magnetic phase diagram were determined, and this system showed to have “low spin state” with 1µB per Co. Some discussions were given from the theoretical stand points. © 1969, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.