Magnetization steps of nearest-neighbor exchange interactions in CdS(Co) and CdSe(Co) in fields to 60 tesla

Abstract The first of three expected magnetization steps (MSTs), due to the nearest-neighbor (NN) antiferromagnetic exchange J 1 between Co 2+ pairs in CdS(Co) and CdSe(Co), is observed by differential magnetization measurements in pulsed magnetic fields up to 60 T. In contrast with earlier results on CdS(Mn) which showed MSTs in pulsed fields much narrower by thermal broadening, the MSTs of the Co substituted materials are much broader, extending from about 35 to 55 T. The broad CdS(Co) MST shows structure due to the two inequivalent NN sites in the wurtzite structure. For Cd 1−x Co x S, an average J 1 k B = −30.6 ± 1.7 K is observed for a single crystal with x = 0.036 and −32.1 ± 1.7 K for a multicrystal with x = 0.064. For multicrystalline Cd 1−x Co x Se with x = 0.046, the broad MST has a maximum corresponding to J 1 k B = −31.0 ± 2 K . The effects of more-distant neighbors and crystalline fields are discussed.