We report the polyvinylpyrrolidone (PVP) encapsulated MnZn ferrite (Mn0.8Zn0.2Fe2O4/PVP) nanocomposite
for low-temperature magnetic properties prepared by the facile one-pot sol-gel route. The transmission electron
microscopy analysis revealed spherical shape ferrite particles in a polymer matrix (Mn0.8Zn0.2Fe2O4/PVP
nanocomposite) with an average particle size of 11.6 nm. The Rietveld refinement of X-ray diffraction (XRD)
data revealed the pure cubic spinel structure formation. The lattice parameter is 8.3825 Å, and the average
crystallite size is 10 nm evaluated from XRD data. Raman spectroscopy analysis is in agreement with XRD
results. The temperature-dependent magnetization analysis disclosed the effective anisotropy constant Keff, the
value of 3.0 × 104 J/m3. The meticulous investigation of magnetic field-dependent magnetic properties from 2 K
to 350 K unveiled superparamagnetic (SPM) behavior. From the electron spin resonance (ESR) analysis, the
calculated g value and spin-spin relaxation time (T2) are 2.03 and 2.52 × 1011 sec, respectively, which confirms
the SPM behavior.