Magnetic properties of multiferroic $K3Cr2Fe3F15$ Available to Purchase

The local electronic and structural as well as the macroscopic magnetic properties of $K3Cr2Fe3F15$ have been studied between room temperature and 4 K. The system has been found to be isostructural with ferroelectric and weakly ferrimagnetic $K3Fe5F15$ above the ferroelectric transition temperature $Tc$⁠. The X-band and 216 GHz $Cr3+$ electron paramagnetic resonance (EPR) spectra as well as the magnetic susceptibility and Mössbauer data show the existence of two magnetic relaxor type transitions around 37 and 17 K. The $K39$ magic angle sample spinning NMR, EPR, and the Mössbauer data further demonstrate the existence of two nonequivalent Fe, Cr, and K sites in the unit cell as well as the presence of rapid exchange at higher temperatures. The observation of the $Fe2+$ EPR and Mössbauer spectra shows that the $Fe2+$ ion is in a high spin state.