Exchange bias and training effect in Ni/Ag-doped NiO bilayers

• Published in: Journal of magnetism and magnetic materials Vol. 322; no. 5; pp. 542 - 547
• Main Authors: Yang, P.Y., Zeng, F., Pan, F.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-03-2010; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Exchange bias; Interfacial magnetic properties (multilayers, magnetic quantum wells, superlattices, magnetic heterostructures); Magnetic properties and materials; Magnetic properties of surface, thin films and multilayers; NiO thin films; Physics; Training effect; NiO thin films; Exchange bias; Training effect; Grain size; Atomic force microscopy; Polycrystals; Spin density; XRD; Silver Nickel Oxides Mixed; Thin films; Nanoparticles; Cathode sputtering; Transmission electron microscopy; Coercive force; Chemical composition; Nickel; Exchange interactions; Bilayers
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2009.10.012

A series of polycrystalline Ag-doped Ni
1−
x
Ag
x
O/Ni bilayers with
x up to 0.2 were prepared by magnetron sputtering. X-ray diffraction, atomic force microscopy and transmission electron microscopy analyses reveal that Ag doping significantly reduces the mean NiO grain size and leads to the appearance of Ag nanoparticles on the surface of the Ag-doped NiO films. As
x increases, the exchange bias field and coercivity at room temperature decrease as a consequence of the reduced thermal stability of smaller NiO grains and the screening effect resulting from the interfacial Ag nanoparticles. At lower temperatures, a slight enhancement of the exchange bias field is observed in the Ag-doped sample, indicating that the Ag doping increases the uncompensated NiO spin density. In addition, our studies find that the training effect of the Ag-doped sample can be well described by a spin configurational relaxation model, regardless of the presence of Ag nanopartiles at the interface.