Abstract
An interesting field induced antiferromagnetic ordering in NiS clusters confined in Y molecular sieve was observed. The NiS cluster-zeolite Y composite exhibits an unusual antiferromagnetic ordering state under a magnetic field of 0.724–1.164 T and paramagnetic behavior out of this field region. The antiferromagnetic ordering can be stable up to 180 K. The phenomenon may be understood by the concept of energy level crossing due to intracluster interaction at a certain magnetic field.