Multifunctional properties of CoNi alloy embedded in the SiO2 host: Role of interparticle interaction

Nanocrystalline CoNi alloy is synthesized using sol–gel technique having average size ∼8.5∼8.5 and View the MathML source∼12nm. High-resolution transmission electron microscopy confirms absence of any oxide phase at the grain boundary. We observe multifunctionality ascribed to large loop shift after the field-cooling and saturation magnetization (M S) depending on interparticle interaction in CoNi alloy embedded in SiO2 matrix. A large loop shift 1.2 kOe is noticed at 5 K for 10.5% volume fraction (ϕϕ). The loop shift decreases with increasing temperature and vanishes around View the MathML source∼210K where a maximum is observed in zero-field-cooled magnetization. The loop shift decreases with decreasing ϕϕ and vanishes at ϕ=0.01%ϕ=0.01%. Interestingly, M S increases with decreasing ϕϕ and value at ϕ=0.01%ϕ=0.01% approaches to the calculated value of MS for the bulk counterpart. A model has been proposed with ferromagnetic-core and disordered magnetic-shell structure to interpret the results.