Unraveling the structural and magnetic characteristics of Mg doped CoCr2O4

• Mg-doped CoCr2O4 synthesized via sol–gel auto-combustion. • X-ray diffraction confirmed single-phase cubic spinel structure, Fd-3 m, 9.75 nm crystallite size. • XPS identified Co 2+ , Cr 3+ , Mg 2+ , and O 2– ions. • FC/ZFC curves indicated superparamagnetic blocking at Ts, with ZFC showing negative magnetization at 53 K under 50 Oe. • Ferrimagnetic and paramagnetic behaviors observed at 5 K and 300 K in M−H loop measurements up to ± 5 T. In this paper, we explore the structural and magnetic properties of Mg doped CoCr 2 O 4 nanopowder (typical size of 10 nm) synthesized via the sol–gel auto-combustion method. X-ray diffraction, XPS, and FTIR spectra confirm spinel structure (space group Fd-3 m ) with Mg 2+ doped at Cr 3+ . Interestingly, temperature-dependent magnetizations show various magnetic transitions between 5–300 K. While they show ferrimagnetic ordering below Curie temperature of 100 K (CoCr 2 O 4 ) to 80 K (CoCr 1.8 Mg 0.2 O 4 ) samples, the irreversibility between FC and ZFC curves at blocking temperature attribute to spin blocking nature of nanoparticles. Finally, at very low temperatures (13–26 K), magnetizations again rise indicating spin-spiral transition of CoCr 1.8 Mg 0.2 O 4 . Furthermore, the effect of these transitions on M−H loop can be evident in terms of coercivity, saturation magnetization, and non-saturation behavior at high magnetic fields.