Study of Spin Dynamics in Exchange Bias Based Metal Oxide Systems

Abstract

Interfaces in magnetically coupled (FM/AFM) systems play a vital role in novel newlinespintronics devices. Importantly, the dynamic behaviour of the interface spin newlinestructures enables the rise of progressively low dimension magnetic read heads which newlineare of major importantance for non volatile recording media. Exchange Bias and its newlineaccompanying properties are fundamental magnetic coupling phenomenon undergoes newlineat the interfaces of AFM/FM and Hard/Soft magnetic systems. newlineExchange Bias and its related magnetic properties have been studies on singlephase Zn0.3Ni0.7Fe2O4 ferrite nanoparticles, MnFe2O4/and#945;-Fe2O3, NiFe2O4/CoO, newlineCoFe2O4/NiO nanocomposite systems. Among them CoO, and#945;-Fe2O3 and NiO are newlineantiferromagnetic (AFM) but NiFe2O4, CoFe2O4, and MnFe2O4 are ferrimagetic newline(FiM). It has been well established that antiferromagnets can pin the newlineferro/ferrimagnets and lead to exchange Bias. Large Exchange Bias field up to 2.2kOe newlineobserved at 5K in the NiFe2O4 /CoO system can be well interpreted by MeiklejohnBean model. However, the Exchange Bias field of 555 Oe and 305Oe are observed at newline5K in CoFe2O4/NiO and NiFe2O4/CoO respectively. This shows that, Exchange Bias newlineis well described by Meiklejohn- Bean model if the anisotropy energy is larger than newlinethe interface exchange energy. Observation on single phase Zn0.3Ni0.7Fe2O4 ferrite newlinenanoparticles revealed the freezing of interfacial spins which were the cause of the newlineloop shift causing large exchange bias with high anisotropy.