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Title: Metallic magnetism and change of conductivity in the nano to bulk transition of cobalt ferrite

Variations in conductivity with particle size have been observed in cobalt ferrite, when synthesized by solgel auto-combustion method. Impedance analysis reveals metallic and semiconducting behavior at room temperature for a particle size of 6 nm and 52 nm, respectively. Upon thermal activation, metallic to semiconducting phase transition has been observed as a function of particle size and vice-versa. Grainboundary Resistance (R{sub gb}), increased drastically with particle size (19 MΩ for 6 nm and 259 MΩ for 52 nm) at room temperature. AC conductivity and dielectric constants exhibit similar metallic to semiconducting phase transition at 6 nm and semiconducting behavior at 52 nm with temperature in the selected frequencies. Enhanced magnetic moment with an increase in the grain size along with decreased coercivity (1444 G to 1146 G) reveals transition from single domain to multi-domain. Increased inter-particle interaction is responsible for metallicity at the nano level and on the contrary semiconductivity is attributed to bulk.
Authors:
; ;  [1] ;  [2] ;  [3]
  1. Department of Physics, Pondicherry Engineering College, Puducherry–605 014 (India)
  2. Department of Physics, Sri Manakula Vinayagar Engineering College, Puducherry–605 107 (India)
  3. Department of Chemistry, Pondicherry Engineering College, Puducherry–605 014 (India)
Publication Date:
OSTI Identifier:
22259299
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 114; Journal Issue: 18; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; COBALT; COERCIVE FORCE; COMBUSTION; FERRITE; FERRITES; GRAIN SIZE; IMPEDANCE; MAGNETIC MOMENTS; MAGNETISM; PARTICLE INTERACTIONS; PARTICLE SIZE; PERMITTIVITY; PHASE TRANSFORMATIONS