Comprehensive scrutiny on the low temperature magnetism and hyperthermia efficiency of greenly synthesized biocompatible Zn_0.25Ca_0.25Fe_2.5O₄ nanoparticles

Abstract The present study comprehensively scrutinizes the complex magnetism and hyperthermia efficiency of greenly synthesized Zn 0.25 Ca 0.25 Fe 2.5 O 4 nanoparticles (ZNCF NPs). ∼23 nm sized ZNCF NPs in single phase fcc-spinel symmetry were successfully produced through sugarcane juice-mediated self-combustion tactics. Biocompatibility examination against BEAS-2B cell lines indicated a safer limit of ZNCF NPs as 1 mg. Exhaustive field (upto ±70 kOe) and temperature-dependent (10 K to 300 K) dc-magnetization measurements showed that ZNCF NPs are in the ferrimagnetic (FiM) phase at low temperatures and superparamagnetic (SPM) along with minute magnetically hard FiM component at 300 K. 57 Fe-Mössbauer analysis validated SPM (43%) and FiM (57%) at 293 K and FiM state at low temperatures. Observed isomer shift revealed that the majority of Fe ions are in a high spin Fe 3+ state along with Fe 2+ ions in ZNCF NPs. Shifting in the real part of ac—susceptibility data toward the higher temperature side upon increasing frequency and obeying Vogel–Fulcher law affirmed collective freezing of superspins below freezing temperature ( T f = 200 K). Dynamic scaling fit yielded relaxation time of ∼10 −12 s, Mydosh parameter (=0.021) and critical exponent (8.9) ascertaining superspin glass (SSG) state in ZNCF NPs below glass temperature ( T g = 220 K). Furthermore, SSG phase at low temperatures is approved by archetypal experimental signatures like ageing, memory and rejuvenation. The induction heating characteristics of ZNCF NPs probed via infrared thermography yielded intrinsic loss parameter in the 0.26 nHm 2 kg −1 –5.10 nHm 2 kg −1 range. Linear response theory provided non-zero power dissipation for ZNCF (suspension in de-ionized water) functioning range of 6–8 nm with an optimum particle size of ∼7 nm. A prudent analysis asserted that only 18% of NPs contribute to a non-zero SAR value. Overall, this research is an exhaustive investigation of the complex magnetism and hyperthermia efficiency suitable for mild hyperthermia applications.