ON THE "HELICAL" ANTIFERROMAGNETISM OF GADOLINIUM

Magnetic properties of Gd in weak fields are measured. The magnetizatton drops sharply at temperatures from THETA /sub 1/= 210 deg K = 210 deg K to the Curie point THETA /sub 2/ = 290 deg K. Sharp bre aks observed in magnetization isothermals sigma (H) are similar to those observed in dysprosium at critical fields corresponding to destruction of helical antiferromagnetism. It is suggested that a helical spin structure exists in gadolinium at temperatures between THETA /sub 1/ and THETA /sub 2/. However, application of very weak fields (H/sub k/~ 0-15 gauss) is sufficient to destroy this structure. (auth)