Interplay of bulk and surface on the magnetic properties of low temperature synthesized nanocrystalline cubic Cu1−xZnxFe2O4 (x=0.00, 0.02, 0.04 and 0.08)

• Low-temperature (200 °C) synthesis of cubic ZnxCu1−xFe2O4 nanoparticles.
• Superparamagnetic to ferrimagnetic transition with increasing Zn content at 300 K.
• High surface effects at 10 K for nanoparticles with lesser Zn concentration.
• Spin-glass-like state, unsaturated M(H) loops, abrupt HC, MS and Keff at 10 K.
• Disappearance of surface effects at 10 K for nanoparticles with high Zn content.

Synthesis of Cu1−xZnxFe2O4, (x=0.00, 0.02, 0.04 and 0.08) nanoparticles by a low-temperature combustion method is achieved and its structural and magnetic characterizations are performed. X-ray powder diffraction (XRD) study and high resolution transmission electron microscope (HRTEM) images confirm the formation of single cubic phase of nanocrystalline copper ferrite. The inter-planar spacing (d) and particle size increases with increasing Zn content. Cation distribution of mixed spinel Cu1−xZnxFe2O4 nanoparticles are estimated by Fourier transformed infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and further verified by 57Fe Mo¨ssbauer spectroscopy. Detailed magnetic properties are studied by means of Field Cooled (FC) – Zero Field Cooled (ZFC) magnetization measurements and hysteresis loops at various temperatures by the physical property measurement system (PPMS). A transition from superparamagnetic state to ferrimagnetic state is observed as the Zn concentration increases in Cu1−xZnxFe2O4 nanoparticles. The temperature dependence of intrinsic magnetic parameters, i.e., coercivity (HC), saturation magnetization (MS), effective anisotropy constant (Keff) and paramagnetic susceptibility (χp) of Cu1−xZnxFe2O4 reveals the existence of low-temperature spin-glass-like state, which is more prominent for smaller particles and starts to disappear with increasing Zn concentration.