AC Magnetic Susceptibility of the Assembled-Metal Complex {NBu_4[Fe^<II>Fe^<III>(ox)_3]}_∞ (Bu=n-C_4H_9, ox=oxalato)

概要

論文の詳細を見る
AC magnetic susceptibility (χ_AC = χ'- iχ'') of {NBu_4[Fe^<II>Fe^<III>(ox)_3]}_∞ was measured in the 4-50K range for different frequencies (0.1-1000 Hz). Both of the χ'(T) and X''(T) plots showed two peaks in two temperature regions: 4-33 K and 33-50 K. The χ'(T) and χ''(T) peaks in the 33-50 K range can be associated with the magnetic phase transition at the Neel temperature (43.3 K). However, the χ'(T) peak in the 4-33 K range was found to be shifted towards lower temperature from 15.5 K to 13.5 K with increasing frequency, accompanied by a decrease in peak height. The fractional relative change in the peak temperature per decade change in frequency was calculated. The χ''(T) in the 4-33 K range exhibited a broad peak around 25 K. The frequency dependence of χ'(T) and χ''(T) in the 4-33 K range occurred in the region where the irreversibilities in the ZFC (zero-field-cooled)-FC (field cooled) susceptibilities appeared. In this temperature range, a small heat capacity anomaly was detected and the negative magnetization effect took place in earlier reports. The wait-time dependence study of ZFC magnetization revealed an aging phenomenon. The frequency dependent peaks observed in the AC susceptibility and the aging phenomenon occurred below the Neel temperature might be indicative of the existence of a spin glass-like state in the present material at low temperatures.
社団法人日本物理学会の論文
2002-09-15