Magnetism of C₆Eu. I. Existence of the Four-Spin Exchange Interactions

Abstract

High field magnetizations of europium graphite intercalation compound C₆Eu have been measured and a clear metamagnetic plateau with 1/3 of the full moment is observed at 4.2 K. Analysis of the magnetization process has revealed the existence of weak four-spin exchange interactions in addition to the usual two-spin exchange. This is the first clear evidence of the four-spin exchange coupling in the Ruderman-Kittel-Kasuya-Yosida (RKKY) type interaction system.