Exchange bias in Fe/Ir20Mn80 bilayers: Role of spin-glass like interface and ‘bulk’ antiferromagnet spins

Abstract

We have performed magnetic measurements like temperature (T), cooling field (H FC ) dependence of exchange bias (EB) and training effect to investigate the magnetic nature of the interface of the Fe/Ir 20 Mn 80 systems. Thin film bilayer samples of different thicknesses of Ir 20 Mn 80 have been prepared by dc magnetron sputtering at room temperature. The variation of exchange bias field (H EB ) with the increase in thickness of Ir 20 Mn 80 predicts the antiferromagnet (AFM) 'bulk' spins contribution to EB. Exponential decay of H EB and coercive field (H C ) with temperature reveals the presence of spin glass (SG) like interface. Also, the decrease of H EB with increasing H FC confirms the SG like frustration at the interface. Further, the fitting of training effect experimental data envisages the presence of frozen and rotatable spins at the magnetically frustrated interface of these EB systems. KeywordsSpin glass like interface; frozen and rotatable spins; 'bulk' AFM spins; exchange bias; exponential decay

Evidence of Spin-Glass state in Molecular Exchange-Bias System

“…In figure 2, in the case of ZFC measurements, H c monotonically increases with decreasing temperature with an increase in H ex below T EB of ∼50 K in CoPc devices and 30 K in the case of MnPc devices. Here, based on our understanding of FM/AFM [19,37,38] or FM/spin-glass exchange-bias system [29], the enhancement in H c relative to the reference-Fe can be understood to arise from two additive but competing effects -surface exchange induced magnetic anisotropy (K i ex ) in the bottom Fe layer and softer domains or frustrated spin centers in the hard surface layer matrix that couple with the bottom Fe layer and partially rotate upon magnetization reversal. Generally, the latter effect depends on interface-disorder and spin-frustration and its strong presence leads to a drop in H c at lower temperatures caused by surface domain freezing, whereby they stop contributing to the H c enhancement [19,29,39].…”

Dependence of Exchange Bias on Interparticle Interactions in Co/CoO Core/Shell Nanostructures

“…Despite intensive experimental research in the field, there are phenomena like spontaneous EB [17], EB in alloys and compounds [18,19], EB in single phase magnetically inhomogeneous materials [20] or EB in thin films [21,22] that are still drawing attention because of the urge to understand new fundamental physics. Furthermore, EB reveals a wide range of potential applications in recording media to overcome the superparamagnetic (SPM) limit [23], field sensors [24], read heads [25], giant magnetoresistance (GMR) based devices [26] and many more as well.…”