pair-controlled photomagnetism and spin-glass freezing in CoFe Prussian blue analogues
Phys. Rev. B 114, 134421 – Published 16 September, 2026
DOI: https://doi.org/10.1103/7lsb-3xgf
Abstract
We investigate the interplay between photomagnetism and spin-glass freezing in CoFe Prussian blue analogues through controlled reacting time and dynamic magnetic analysis. Reacting time continuously modifies the internal CN-bridged pair populations while keeping the average Fe-vacancy concentration low, thereby providing a route to tune the magnetic exchange network without introducing significant additional defect disorder. Fourier-transform infrared measurements show that the fraction of pairs decreases systematically with reacting time, accompanied by an increase in pairs. Correspondingly, the ground-state ferrimagnetic response is progressively weakened, as reflected by reduced coercivity, lower high-field magnetization, and a downward shift of the Curie temperature. The spin-glass behavior is suppressed in parallel, with the freezing temperature shifting to lower values and the ac susceptibility peak eventually disappearing in aged samples. Despite this suppression, all samples retain a pronounced photomagnetic response under illumination. Light irradiation enhances the magnetization and coercivity and, more importantly, strengthens or even induces spin-glass freezing in samples with more reacting time. In the defect-poor sample, Mydosh analysis and Vogel-Fulcher fitting show that illumination increases the freezing temperature, the freezing-limit temperature , and the activation energy , indicating strengthened interaction-dominated freezing and a more stable glassy energy landscape. These results identify pairs as the key microscopic units linking photomagnetism to nonequilibrium spin freezing and demonstrate that reacting time and light act as two opposite control parameters on the same exchange network in CoFe Prussian blue analogues.
