Materials Science Communication A study of slow spin±spin relaxation in the intercalation compound FeOCl[FeCp 2 ] 0.16 G.G. Siu a , Z.P. Bai b , Z. Yu a,b,* , N. Fang b , F.N. Shi b , R.C. Liu b , X.Z. You b a Department of Physics and Materials Science, City University of Hong Kong, Hong Kong, China b Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, Nanjing University, 210093, Nanjing, China Received 19 October 1998; received in revised form 31 January 1999; accepted 12 February 1999 Abstract Mo Èssbauer spectroscopy, XPS and EPR are used to investigate the slow spin±spin relaxation in the intercalation compound FeOCl[FeCp 2 ] 0.16 . The results show that the intercalant molecules of ferrocene are completely oxidized in the intercalation. # 1999 Elsevier Science S.A. All rights reserved. Keywords: Mo Èssbauer spectroscopy; Intercalation; Spin±spin relaxation 1. Introduction Layered metal oxychlorides MOCl (M  Fe, Ti, V, Cr, In) are anisotropic and reactive compounds. Various organic and inorganic molecules can be intercalated into their interlayer sites. These intercalation compounds has pro- spects to become a new type of low dimensional conductors or superconductors [1]. Physical and chemical studies of MOCl and its intercalation compounds have been made for decades [2±6]. FeOCl can directly intercalate ferrocenes (FeCp 2 ) [7,8], and they are investigated by various techni- ques, in which Mo Èssbauer spectroscopy is important for studying electron transfer and mixed valence. Investigation on intercalation compound FeOCl- [FeCp 2 ] 0.16 have not achieved unanimous conclusion about the temperature effect on its antiferromagnetic ordering [8±11]. Even the spin direction is uncertain. Some studies suggest that the long range magnetic ordering is along the intralayer b-axis, but others favor three-dimensional mag- netic ordering. The time-scale of the magnetic ordering or charge transfer in the compound could be the major factor affecting the results. In order to clarify the effect of the time- scale, we carry out Mo Èssbauer measurements (time-scale 10 7 s) together with experiments of electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) which characterize process of 10 2  10 4 s and 10 17 s, respectively. 2. Experimental FeOCl was prepared by heating the mixture of FeCl 3 and Fe 2 O 3 in molar ratio 4 : 3 at 3708C in an evacuated quartz tube for 1 week. The intercalation FeOCl[FeCp 2 ] 0.16 was prepared by the method mentioned in [8]. Mo È ssbauer experiments were carried out using a 57 Co=Pd source and a constant-acceleration spectrometer to collect the transmission spectra at room temperature. The spectro- meter was calibrated using a standard a-Fe foil. The isomer shifts (I.S.) are determined relative to the center of the a-Fe spectrum. The MOSFUN program was used to determine the Mo Èssbauer parameters [12]. The X-ray powder diffraction analysis was performed using a Shimadzu diffractometer with Cu Ka radiation. A Bruker Er 200-D-SRC spectro- meter was used for EPR with magnetic ®eld scanning in the range from 0 to 6800 G and microwave frequency of 9.7746 GHz. XPS spectra were recorded by a VG ESCA- LAB MK-II spectrometer with Mg Ka excitation for powder sample on a double-side sticking-tape. Core level binding energy was measured for Fe ions in the sample. The energy calibration was made with the C 1s (E b  284.3 eV) level of adventitious carbon. 3. Results and discussions As preliminary investigations X-ray powder diffraction and IR spectroscopy are preformed on FeOCl and FeOCl- [FeCp 2 ] 0.16 . The intercalation compound has an interlayer Materials Chemistry and Physics 59 (1999) 168±170 *Corresponding author. 0254-0584/99/$ ± see front matter # 1999 Elsevier Science S.A. All rights reserved. PII:S0254-0584(99)00047-4