Magnetization and electron spin resonance of Fe impurities in (TMTSF)_2AsF_6: magnetic-field-dependent interaction between impurity spins and spin-density waves

摘要

A new spin-density-wave (SDW) system with magnetic impurities (TMTSF)_2(AsF_6)_(1-x)(FeCl_4)_x was prepared and its magnetic properties were studied by means of magnetization and electron-spin-resonance measurements. The anisotropic g-value and comparison of the Fe concentration with the Curie constant indicate that the Fe~(3+) ions are in a low-spin state. We also found that the magnetization curve of the impurity spins in this compound shows an anomalous behavior. This behavior can be explained if one assumes a field-dependent magnetic interaction between the Fe~(3+) spins and the SDW moment. We suppose that the field dependence of the SDW pinning potential is responsible for this phenomenon.