Hyperfine interaction and tuning of magnetic anisotropy of Cu doped CoFe2O4 ferrite nanoparticles

Microstructural, magnetic, and hyperfine characterizations of Cu‐doped cobalt ferrite nanoparticles

“…All the samples contain these five characteristics peaks of nano‐sized CoFe 2 O 4 . The doping of Cu 2+ ions in octahedral (B) sites causes Jahn‐Teller distortion, through which the cubic symmetry of octahedral (B) site turns in to tetragonal symmetry . The appearance of the shoulder‐like feature appeared in Raman peaks with increase in Cu 2+ ions concentration is due the lowering of space group symmetry in octahedral (B) site.…”

“…The observed sextet patterns in Mössbauer spectra are the superposition of sextets originating from the tetrahedral (A) sites and octahedral (B) sites due to magnetic hyperfine interactions which result in nuclear Zeeman splitting of energy levels . The fitted sextet patterns having lower value of isomer shift correspond to tetrahedral sites and those with higher value of isomer shift is related to octahedral sites . The hyperfine parameters obtained from fitting the Mössbauer data are listed in Table .…”

“…The deviation from cubic symmetry due to small size generates electric field gradient of varying magnitude and direction. The internal hyperfine magnetic field is resultant of various interactions, such as polarization of core s ‐electrons by magnetic moment of d ‐electrons ( H core ), super transferred fields by magnetic moment of neighboring cations ( H STHF ), dipolar field of magnetic ions ( H D ) and transferred fields ( H THF ), described by the relation:…”

“…In our spinel ferrite system, the superexchange interactions dominate the crystal fields thereby the weak crystal field prefers high spin configuration and Jahn‐Teller distortion for a particular transition metal ion. In this work, our aim is to synthesize Cu‐doped cobalt ferrite nanoparticles and study the correlation between the elastic and magnetic properties as a result of the induced Jahn‐Teller distortion …”

“…The origin of this ferrimagnetic ordering in cobalt ferrite is due to superexchange (A-O-B) interaction between tetrahedral (A) and octahedral (B) sublattices which is stronger than both A-O-A and B-O-B intra-sublattice interactions. [3][4][5][6][7][8] In case of magnetic nanoparticles, the existence of large number of atoms at the surface due to high surface to volume ratio and finite size effects (single domain structure, quantum confinement of electrons) is responsible for exhibiting several interesting and superior properties in comparison to bulk materials. The coordination number of surface atoms is reduced in comparison with the atoms that are present in core of the nanoparticle, which produces different surface effects such as spin canting, spin disorder, and presence of magnetic dead layer.…”