Co[sub x]Ni[sub 1-x]O thin films and CoO-NiO superlattices: Structure, magnetic properties and exchange anisotropy with Ni[sub 81]Fe[sub 19]

Miscellaneous · Fri Jan 01 00:00:00 EST 1993

OSTI ID:6916691

Carey, M J

The production, structure and magnetic properties of Co[sub x]Ni[sub 1[minus]x]O thin film alloys, CoO-NiO superlattices and CoO-NiO bilayers are studied. Both polycrystalline and epitaxial single crystal films are produced by reactive sputtering. Single phase Co[sub x]Ni[sub 1[minus]x]O metastable alloys were produced. The epitaxial single crystals are of high crystalline quality and the interfaces of CoO-NiO superlattices are highly coherent. Shifted hysteresis loops are used to explore the exchange anisotropy properties of Co[sub x]Ni[sub 1[minus]x]O/Ni[sub 81]Fe[sub 19] and CoO-NiO superlattice/Ni[sub 81]Fe[sub 19] coupled bilayers. A shifted hysteresis loop is observed for Co[sub x]Ni[sub 1[minus]x]O/Ni[sub 81]Fe[sub 19] couples. Co[sub x]Ni[sub 1[minus]x]O/Ni[sub 81]Fe[sub 19] couples exhibit an optimum exchange anisotropy near compositions of x = 0.5, with properties comparable to FeMn/Ni[sub 81]Fe[sub 19]. The ordering temperature of Co[sub x]Ni[sub 1[minus]x]O varies linearly with x. CoO-NiO superlattices are ideal for studying the effects of interfacial magnetic coupling since the superexchange interaction restricts the coupling to near neighbors. CoO-NiO superlattices have a single magnetic ordering temperature between the ordering temperatures of CoO and NiO when the constituent layers are thinner than 20[angstrom]. Thick-NiO/thin-CoO/Ni[sub 81]Fe[sub 19] trilayers were produced to investigate the thickness dependence of the oxide-oxide interaction in the superlattices. When the CoO layers are sufficiently thin, the CoO ordering temperature approximates the NiO value, indicating quite strong coupling throughout the CoO layer. The effect of the coupling is much weaker for thicker CoO layers ([ge]30[angstrom]). The superlattice ordering behavior is modeled using a mean field formalism. In superlattices with thick constituent layers, a surprising magnetic coupling is observed.

• Research Organization: California Univ., San Diego, La Jolla, CA (United States)
• OSTI ID: 6916691
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

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