Magnetic exchange interactions and dielectric studies of Zn1–x NixO–NiO composites. (20th July 2017)

• Record Type: Journal Article
• Authors: Joshi, D C; Pramanik, P; Nayak, S; Dasari, K; Choudhary, R J; Thota, S
• Is Part Of: Journal of physics. Volume 50:Number 32(2017)
• Publication Date: 2017-07-20
• Subjects: antiferromagnetism -- Nèel temperature -- exchange integral -- rhombohedral distortion; Physics -- Periodicals; 530
• DOI: 10.1088/1361-6463/aa7826
• Languages: English
• ISSNs: 0022-3727

Abstract

Abstract: We report a detailed study on the nature of magnetic exchange interactions and dielectric properties of Z n 1 − x Ni x O–NiO composites. The magnetic exchange constants | J 1 | and | J 2 | for the two sublattices have been evaluated using both molecular-field approximation ( J 1 ∼ 0.15 meV and J 2 ∼ 1.15 meV for x = 1 ) and Green's-function theory ( J 1 ∼ 0.78 meV and J 2 ∼ 1.77 meV for x = 1 ). Magnitudes of these exchange constants determined from the Green's-function analysis are consistent with the values obtained from the spin-wave dispersion curves ( J 1 ∼ 0.137 meV and J 2 ∼ 1.90 meV for x = 1 ) and Raman scattering ( J 2 ∼ 1.98 meV). Moreover, the carrier activation energy ϵ h (̃59.9 meV) and nearest-neighbor exchange coupling parameters J i j (̃1.61 meV) calculated from the temperature dependence of ac resistivity ρ a c ( T ) across the antiferromagnetic Néel temperature ( T N ) of NiO using a small-polaron model involving spin-dependent activation energies are compared with the theoretical estimations from the Green's-function theory. In addition, the role of oxygen stoichiometry in the temperature variation of J i j, ϵ R, ρ ac and the unit-cell volume V C have been discussed.