EPR evidence of paramagnetic to spin glass transition in Zn1−xMnxSe:Fe2+ single crystals

In this work, the paramagnetic-to-spin glass transition in Zn1–xMnxSe:Fe2+ single crystals by using the analysis of temperature-dependent electron paramagnetic resonance (EPR) spectra were investigated. The transition is characterized by the broadening and a decrease in the amplitude of a single Lorentzian resonance line at g ~ 2.01, with critical freezing temperatures Tf at approximately 5.7 K for x = 0.2 and 8.0 K for x = 0.3. At lower temperatures, EPR spectra reveal three distinct paramagnetic centers attributed to Fe3+ ions at g ~ 4.3, strongly interacting Fe ions at g ~ 2.05, and a vacancy-type center at g ~ 2.003. These results indicate that iron doping promotes Mn clustering and stabilizes the spin glass phase, affecting the magnetic properties of Zn1–xMnxSe.