Spin-valve giant magnetoresistive films with antiferromagnetic Ir-Mn layers

Abstract

We succeeded in developing CoFe spin valves with an antiferromagnetic Ir-Mn film. Ir-Mn single-layer films and spin valves of Ta(5 nm)/Ir-Mn(8 or 9 nm)/Co90Fe10(x nm)/Cu(3 nm)/Co90Fe10(3 nm)/NiFe(2 nm)/CoZrNb(10 nm)/ (x=2, 2.3, 2.6 nm), prepared by the sputtering method, showed the crystal structure of a fcc (111) preferred orientation. As-deposited CoFe spin valves with Ir-Mn exhibited an interfacial exchange coupling energy of J=0.192 erg/cm2 (Hua∼640 Oe at tCoFe=2 nm), that was the highest ever reported for as-deposited antiferromagnetic films, such as NiO, NiMn, and FeMn. Furthermore, CoFe spin valves with Ir-Mn exhibited a higher blocking temperature of 260 °C, and a higher MR ratio of 6.37% than the spin valves with FeMn film. After annealing, the MR ratio increased to 7.82%. On the other hand, the Hua decreased about 100 Oe after annealing. The Hua-T curve was, however, improved and the Hua at 100 °C increased to 400 Oe. The decrease in Hua was not observed after second annealing and seems to be stabilized by first annealing.

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.…”

The effect of cyclic annealing treatments on magnetoresistance in IrMn‐pinned top and bottom spin valves

“…Therefore, exchange coupled IrMn(~80 Å)/CoFe bilayer is suitable for narrow gap head structure [2,6], since IrMn shows a high H ex at smaller layer thickness than other ordered AFM films, such as NiMn and PtMn [1,7].…”

“…1 Introduction IrMn has been identified as a promising antiferromagnetic (AFM) material for use in spin valve (SV) giant magnetoresistance (GMR) heads in high density magnetic recording [1][2][3] due to its high exchange coupling field (H ex ), high blocking temperature (T B ), and low critical thickness (~80 Å) [4,5]. Therefore, exchange coupled IrMn(~80 Å)/CoFe bilayer is suitable for narrow gap head structure [2,6], since IrMn shows a high H ex at smaller layer thickness than other ordered AFM films, such as NiMn and PtMn [1,7].…”