A model of the temperature dependence of exchange bias in coupled ferromagnetic∕antiferromagnetic bilayers

Abstract

A granular level model of the magnetic properties of coupled ferromagnetic/antiferromagnetic layers is used to calculate the temperature dependence of the exchange bias. The predicted results are in good qualitative agreement with experiment. Agreement with experiment requires the introduction of the temperature dependence of the auisotropy constant of the antiferromagnetic layer.

Temperature and set field dependence of exchange bias training effects in Co/NiO/[Co/Pt] heterostructures with orthogonal easy axes

“…Both the Co and the [Co/Pt] 3 are coupled to an array of independent AFM grains with variable volume and net surface magnetization. Simulations in [42] describe an effective energy barrier to switching within each AFM grain that depends on the balance between the interface coupling (which lowers the barrier) and the anisotropy energy of the AFM. The distribution of grain sizes and coupling strengths leads to a distribution of energy barriers, and the blocking temperature corresponds to the temperature at which the exchange bias field goes to zero for the median energy barrier.…”

A new paradigm for exchange bias in polycrystalline thin films

“…In a more recent work, the same group studied the temperature dependence of exchange bias in bilayer systems [31]. This version of their model takes into account the temperature dependence of the anisotropy of the AF.…”

Temperature dependence of the exchange bias properties of ferromagnetic/antiferromagnetic polycrystalline bilayers

“…In Ref. [21], the blocking temperature is shown to decrease as the exchange field acting on the AF layer from the F layer increases and, in Ref. [22], the coercivity exhibits a peak around the mean blocking temperature due to the instability of the AF layer.…”

“…Our model takes into account the thermal effects on the stability of the AF and F grains unlike the above mentioned investigations [21,22]. Furthermore, the influence of the coupling between F grains and of the grain size dispersion is investigated.…”

“…More recently, a simple theoretical model [19], which assumes that only AF grains in the window between two critical volumes V C and V set contribute to the loop shift, has been used to investigate the EB properties of submicron square plots made up of polycrystalline layers [20]. Besides, to our knowledge, there are only few studies based on a granular model which are carried out using the Monte Carlo (MC) method, although it is very convenient to investigate thermal effects [21,22]. In Ref.…”