Spin glass and exchange bias phenomena in NdSrNiMnO6 nanoparticles: Role of antiferromagnetic antisite disorders

Abstract

We report the discovery of spin glass (SG) and exchange bias (EB) phenomena in NdSrNiMnO6 nanoparticles. Doping at Nd site in the double perovskite compound Nd2NiMnO6, induces antisite disorders leading to antiferromagnetic antiphase boundaries within the system, which are further responsible for the observed phenomena. The role of particle size on these effects has been discussed as the amount of antisite disorder may vary with particle size. We observed a high Curie temperature (TC ∼ 264 K) for small size samples. As the particle size increases, the ferromagnetic (FM) transition becomes indistinct and system transforms to a magnetically frustrated state containing co-existence of FM, antiferromagnetic (AFM) and SG phases. Meanwhile, TC decreases with increasing particle size and the FM ordering becomes unclear for largest particle size sample. The detail investigation of ac susceptibility, memory effect, DC magnetization and magnetic relaxation measurements exposes the SG behavior in the largest particle size sample. By varying the amount of antisite disorders in the NdSrNiMnO6 with increasing particle size, we obtained intrinsic EB effect with a large EB field (∼640 Oe). Further, the EB effect has also been explored by carrying out the cooling field dependent EB measurements in addition to training effect experiments. The exchange interaction between the AFM core and SG like shell of the system is explained through a phenomenological core shell model.