Exchange Bias and Spin-Glass-Like Ordering in ε-Fe3N–CrN Nanocomposites

Abstract

ε-Fe3N–CrN nanocomposite system is synthesized by wet chemical technique. Exchange bias coupling exists at the interface of the ferromagnetic (FM) ε-Fe3N and antiferromagnetic (AF) CrN phases and the FM ε-Fe3N and AF Fe–O–N/Cr–O–N surface layers. However, the exchange bias is not found to be dependent on the CrN concentration and the coupling of the spins at the surface Fe–O–N/Cr–O–N–ε-Fe3N has a dominating influence. The maximum shift in hysteresis loop is observed to be 78 Oe and the low magnitude of exchange bias is attributed to the roughness of AF–FM interface that induces spin-disorder and random exchange anisotropy. The relaxation dynamics study indicates the presence of antiferromagnetic ordering in this system. Below 65 K, the broad peak in zero-field cooled (ZFC) magnetization curves (TE\\congTf) indicates the presence of unidirectional anisotropy and spin-glass-like ordering. The spin-glass-like ordering, which arises from the freezing of the clustered randomly oriented spins, is confirmed from the frequency dependence in AC susceptibility measurements and dynamic scaling analysis.