Influence of spherical assembly of copper ferrite nanoparticles on magnetic properties: orientation of magnetic easy axisElectronic supplementary information (ESI) available: Atomic absorption spectroscopy (AAS) analysis (Table S1), X-ray diffraction analysis, magnetic property analysis (orientation of magnetic easy axis). See DOI: 10.1039/c4dt00093e

• Main Authors: Chatterjee, Biplab K, Bhattacharjee, Kaustav, Dey, Abhishek, Ghosh, Chandan K, Chattopadhyay, Kalyan K
• Format: Journal Article
• Language: English
• Published: 06.05.2014
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c4dt00093e

The magnetic properties of copper ferrite (CuFe 2 O 4 ) nanoparticles prepared via sol-gel auto combustion and facile solvothermal method are studied focusing on the effect of nanoparticle arrangement. Randomly oriented CuFe 2 O 4 nanoparticles (NP) are obtained from the sol-gel auto combustion method, while the solvothermal method allows us to prepare iso-oriented uniform spherical ensembles of CuFe 2 O 4 nanoparticles (NS). X-ray diffractometry (XRD), atomic absorption spectroscopy (AAS), infra-red (IR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), 57 Fe Mössbauer spectroscopy and vibrating sample magnetometer (VSM) are used to investigate the composition, microstructure and magnetic properties of as-prepared ferrite nanoparticles. The field-dependent magnetization measurement for the NS sample at low temperature exhibits a step-like rectangular hysteresis loop ( M R / M S ∼ 1), suggesting cubic anisotropy in the system, whereas for the NP sample, typical features of uniaxial anisotropy ( M R / M S ∼ 0.5) are observed. The coercive field ( H C ) for the NS sample shows anomalous temperature dependence, which is correlated with the variation of effective anisotropy ( K E ) of the system. A high-temperature enhancement of H C and K E for the NS sample coincides with a strong spin-orbit coupling in the sample as evidenced by significant modification of Cu/Fe-O bond distances. The spherical arrangement of nanocrystals at mesoscopic scale provokes a high degree of alignment of the magnetic easy axis along the applied field leading to a step-like rectangular hysteresis loop. A detailed study on the temperature dependence of magnetic anisotropy of the system is carried out, emphasizing the influence of the formation of spherical iso-oriented assemblies. The spherical assembly of nanoparticles induces a high degree of alignment of magnetic easy axis as compared to randomly oriented nanoparticles which increases the reduced remanence ensuing straightened hysteresis loop.