Thermal stability of Ir–Mn as exchange biasing material

Abstract

We have investigated the strength and the thermal stability of Ir–Mn (18 at. % Ir) as an exchange biasing material for Ni80Fe20 and Co90Fe10, for configurations with the Ir–Mn layer both below and above the ferromagnetic (F) layer. The highest interfacial exchange energy (Jeb=0.13 mJ/m2 at 300 K) was found for 10 nm Ir–Mn deposited above a Co90Fe10 layer. For all configurations investigated the blocking temperature was approximately 560 K. For 10 or 30 nm Ir–Mn above and for 30 nm Ir–Mn below the F layer a remarkable decrease of the exchange biasing at room temperature was found after heating the film, whereas such an effect was not observed for a 10 nm thick Ir–Mn layer deposited below the F layer. This observation, in combination with the results of a relaxation experiment and the lack of experimental evidence for structural changes upon heating, suggests that heating can induce an irreversible change in the magnetic structure of Ir–Mn layers.

Correlation between perpendicular exchange bias and magnetic anisotropy in IrMn∕[Co∕Pt]n and [Pt∕Co]n∕IrMn multilayers

“…These values for are about one order of magnitude smaller than those measured on IrMn exchange-biased systems with inplane magnetization. [17][18][19][20][21][22] Although rather small, the perpendicular interfacial exchange energies for the Co/ Pt-IrMn system are comparable to those measured on similar CoFe/ Pt and Co/ Pt multilayers with an AFM FeMn film on top. 9 To determine the effects of field annealing on the perpendicular magnetic anisotropy of exchange-biased Co/ Pt multilayers we measured the EHE voltage with an in-plane FIG.…”

“…For these structures, differences in ͑111͒ texture, grain size, and interface roughness have been suggested as possible explanations. [17][18][19][20][21][22] Figure 2͑c͒ shows XRD scans on Co/ Pt multilayers with IrMn on the top and IrMn at the bottom. In both cases a ͑111͒ texture is measured for the Pt and IrMn layers.…”

“…IrMn is less corroding than FeMn, and it combines a relatively high interfacial exchange energy ͑ Ϸ 0.2 mJ/ m 2 ͒ with a high blocking temperature of about 250°C. [17][18][19][20][21][22] Recently, it was shown that IrMn can be successfully used to exchange bias systems with out-of-plane magnetization. 23,24 In this paper we study perpendicular exchange bias in Co/ Pt multilayers with an IrMn film at the bottom or on top.…”

Sensor properties of a robust giant magnetoresistance material system at elevated temperatures

“…The temperature value that is obtained if these curves are extrapolated to zero field is in good agreement with the blocking temperature that was determined from magnetization measurements. 4 It is remarkable that the relative decrease of the exchange-biasing field is much smaller for the films with an exchange-biased AAF. This is obviously a big advantage for sensor applications, in particular in automotive and industrial environments.…”

“…Over a large temperature range the GMR ratio decreases approximately linearly. Just below 290°C ͑i.e., the blocking temperature of our Ir-Mn films͒ 4 it drops to a low value. Despite the absence of exchange biasing above this temperature, there is still a small GMR effect left up to Ϸ350°C.…”