Nature of magnetic ordering in nanocomposites of Zn1-pNipO and NiO

A detailed study of the nature of magnetic exchange interactions and magnetic anisotropy in Zn1-pNipO/NiO0≤p≤1 two-phase nanocomposites is reported. The exchange constants J1 and J2 have been determined using the molecular field approximation for the two-sublattice model which yields J2̃11.26 meV and J1̃7.17 meV for p=1, consisting with type-II antiferromagnetic ordering (i.e. J2≫J1). Moreover, a core-shell surface layer modelKeff=Kbulk+6KsurfaceD+Kshell1−2dshD−3 has been employed to explain the nature of magnetic anisotropy in these nanocomposites. This model yields the anisotropy constants Ksurface=2.42 erg/cm2, Kbulk=2.61×106 erg/cm3 and Kshell=9.56×105 erg/cm3 for shell thickness dsh̃1.34nm(p=1).183