Electron Magnetic Resonance Spectrum and Magnetic Susceptibility of K4MnCl6 from 1.4° to 300°K

Abstract

The electron magnetic resonance spectrum and magnetic susceptibility of polycrystalline K4MnCl6 have been investigated over the temperature range from 1.4° to 300°K. The susceptibility follows a Curie–Weiss behavior above 95°K with a Weiss constant θ of −7.8°K. Between 13° and 80°K, a Curie–Weiss behavior is still observed but with a θ value of −6.0°K, different than that observed in the higher temperature range. Coinciding with the susceptibility change is a resonance linewidth change from 23 G above 90°K to approximately 175 G below 70°K. The origin of these changes is not known. No evidence for a transition to a magnetically ordered state has been observed, even down to 1.4°K. Comparison of experimental and theoretical resonance linewidths suggest that the dominant superexchange interaction involves next-nearest-neighbor Mn2+ ions. This interaction is conveyed by two intervening Cl− ions. The exchange integral for the next-nearest-neighbor interaction is estimated to be 0.22°K. Results suggest that there is approximately a 0.8% probability for transfer of an electron from a Cl− ion to a Mn2+ ion.