Ultra-thin Co/Pd multilayers with enhanced high-temperature annealing stability

Abstract

Understanding the thermal budget of perpendicular materials is crucial for the potential application perpendicular magnetic tunnel junctions. In this paper, we study the effects of high-temperature rapid thermal annealing on the structural and magnetic properties of ultra-thin Co/Pd multilayers deposited at room temperature. It is shown that perpendicular magnetic anisotropy of ultra-thin Co/Pd multilayers improves with increasing annealing temperature up to 425 °C. This property of ultra-thin Co/Pd multilayers provides increased thermal budgets for CMOS-integrated magnetic devices.

Correlation between Pd metal thickness and thermally stable perpendicular magnetic anisotropy features in [Co/Pd]n multilayers at annealing temperatures up to 500 °C

“…These M 0 values are large compared with the bulk M S value for Co (∼1400 emu/cc), which seems to originate from the Co orbital moment contribution. 11 In particular, compared with those of the 0.2 and 0.3 series, the magnetic properties of all 0.1 series samples deteriorated as the annealing temperature increased, as shown in Figs. 1(a) and 1(d).…”

“…However, the thin Co layer in the 0.1 series is highly susceptible to surface damage during sputtering of the upper Pd layer, as demonstrated for other Co/Pt ML configurations. [11][12][13][14] On the other hand, the 0.2 and 0.3 series with thicker Co layers are more tolerant of the sputtering influence of the upper Pd layer. As a result, the saturation magnetization of the 0.2 and 0.3 series increases as annealing temperature increases, as shown in Figs.…”

“…[5][6][7][8] Among them, artificial ML matrices composed of ferromagnetic and noble metals, such as Co/Pd, Co/Pt, Fe/Pd, and Fe/Pt, have shown that ML matrices are promising candidates for use in p-MTJs. 4,[9][10][11][12] Alternating two ultra-thin layers with different thicknesses in the ML matrix permits appreciable tuning of magnetic characteristics and yields strong PMA features. These PMA properties may originate from possible interface spin-orbit coupling between ferromagnetic/noble metals.…”

“…namely, limited annealing stability. 11,12 The low annealing stability of PMA properties may be related to unknown structural stress or interfaces between ferromagnetic and metal layers. Therefore, much effort has been dedicated towards ensuring annealing stability in p-MTJs that can be operated at more than 400 • C for a wide range of applications, such as high-density and low-power p-STT MRAM devices.…”

Perpendicular magnetic anisotropy in the Heusler alloy Co2TiSi/GaAs(001) hybrid structure

“…Another widespread PMA material class is metallic stacking layers that are also based on transition, noble metals and rare-earth magnets. 10,11 The PMA of these structures has an interfacial origin for which the orbital hybridization and/or the intermixing at the interface promotes the perpendicular spin coupling. 12,13 Since metallic layers should be thin enough for triggering the PMA, the fabrication process of such multilayers and the related devices would be more complicated than a simple layer.…”