Defect-tuning exchange bias of ferromagnet/antiferromagnet core/shell nanoparticles by numerical study

Abstract

The influence of non-magnetic defects on the exchange bias (EB) of ferromagnet (FM)/antiferromagnet (AFM) core/shell nanoparticles is studied by Monte Carlo simulations. It is found that the EB can be tuned by defects in different positions. Defects at both the AFM and FM interfaces reduce the EB field while they enhance the coercive field by decreasing the effective interface coupling. However, the EB field and the coercive field show respectively a non-monotonic and a monotonic dependence on the defect concentration when the defects are located inside the AFM shell, indicating a similar microscopic mechanism to that proposed in the domain state model. These results suggest a way to optimize the EB effect for applications.

Room-temperature ferromagnetism in Ni(ii)-chromia based core–shell nanoparticles: experiment and first principles calculations

“…Monte Carlo simulations were used to show that the presence of defects (vacancy or non-magnetic impurity) at the core-shell interface degrades the exchange bias in FM@AMF CSNs. 20 In a separate study, it was shown from Monte Carlo simulations that spherical FM@AFM CSNs with smooth core-shell interfaces have higher exchange bias (EB) fields than ones having considerable interface roughness. 21 However other studies based on Monte Carlo simulations show that the magnitude of the exchange bias field is enhanced with greater interface roughness in FM@AFM core-shell nanoparticles.…”

Monte Carlo simulations of core/shell nanoparticles containing interfacial defects: Role of disordered ferromagnetic spins

“…As discussed previously by Mao et al [16], in case of FM/AFM nanoparticles the defect at the interfacial region weakens the exchange coupling, leading to the monotonous reduction and enhancement of EB field and coercivity, respectively. As shown in Fig.…”

Nonmagnetic impurities and roughness effects on the finite temperature magnetic properties of core–shell spherical nanoparticles with antiferromagnetic interface coupling

“…It is found that the frustrated spins at the ferromagnetic interface is another pinning-source generating exchange bias phenomenon, in addition to the antiferromagnetic shell spins. Furthermore, the influences of non-magnetic defects on the exchange bias of core-shell nanoparticles have been analyzed by benefiting from Monte Carlo simulation, and it is shown that exchange bias can be tuned by defects in different positions [28]. Apart from these, Evans et al [25] presented exchange-bias calculations for FM core/AFM shell nanoparticles with roughened interfaces.…”