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We review recent developments in magnetic tunnel junctions with perpendicular easy axis (p-MTJs) for nonvolatile very large scale integrated circuits (VLSIs). So far, a number of material systems such as rare-earth/transition metal alloys, L1₀-ordered (Co, Fe)–Pt alloys, Co/(Pd, Pt) multilayers, and ferromagnetic-alloy/oxide stacks have been proposed as electrodes in p-MTJs. Among them, p-MTJs with single or double ferromagnetic-alloy/oxide stacks, particularly CoFeB–MgO, were shown to have high potential to satisfy major requirements for integration.

In this paper, orthogonal experiment was designed pragmatically by five factors and five levels and then considering the content of f-CaO and MgO to determine the process parameters. Carbonation depth, content of free-CaO and MgO were quantitatively analyzed by phenolphthalein indicator, benzoic acid - ethanol standard titration solution and EDTA titration respectively. The volume stability of mortar was measured by autoclave test. The results show that the content of free-CaO of carbonated steel slag aggregate are effected, in the order from influence degree, by moisture, carbonated pressure, carbonated time, carbonated temperature and molding pressure. Their optimal parameters are 12wt.%, 0.15MPa, 8h, 60°C and 9MPa respectively. The specimens with the f-CaO content of more than 3wt.% are all spalled, and though 5wt% of MgO is existed in carbonated aggregate, volume stability mortar is unaffected.