Electron paramagnetic resonance and Mössbauer study of antiferromagnetic K3Cu3Fe2F15

The electron paramagnetic resonance (EPR) spectra of K3Cu3Fe2F15 consist above 85 K of a superposition of two Lorentzians with different intensities, T-dependences, linewidths, and g-factors. The broad line shows an antiferromagnetic (AFM) behavior and the narrow one shows a paramagneticlike behavior. The Mossbauer spectra consist at room temperature of two quadrupolar doublets and below 77 K of two magnetic sextets and one quadrupolar doublet. Below 85 K the broad line EPR disappears and the intensity of the narrow line increases nearly exponentially with decreasing temperature. The broad EPR line originates from regions with local AFM order, whereas the narrow line comes from regions without AFM order, e.g., grain boundaries.