68th Annual Meteoritical Society Meeting (2005) 5086.pdf

MÖSSBAUER STUDY OF IRON PHOSPHIDES EXTRACTED FROM SIKHOTE-ALIN METEORITE. M.Yu. Larionov, V.I. Grokhovsky and M.I. Oshtrakh. Faculty of Physical Techniques and Devices for Quality Control, Ural State Technical University – UPI, Ekaterinburg 620002, Russian Fed- eration. E-mail: [email protected], [email protected], [email protected],

Introduction: The iron nickel phosphides (Fe,Ni)3P are oc- curred in iron meteorites in the forms of schreibersite and rhab- dite. Schreibersite and rhabdite are formed as a result of hetero- geneous and homogeneous nucleation mechanisms, respectively. A comparison of the hyperfine parameters of these phosphides is of interest due to differences of its nature. Methods: The sample of schreibersite was prepared as a powder using mechanically extracted massive schreibersite from Sikhote–Alin meteorite (IIB) that was treated with HCl to re- move kamacite residue. The small rhabdite crystals were ex- tracted electrochemically from Sikhote–Alin meteorite (IIB) and used for sample preparation. Mössbauer spectra were measured at room temperature using Mössbauer spectrometer SM–2201 with high accuracy, stability and sensitivity in transmission ge- ometry with moving absorber. Discussion: Mössbauer spectra of schreibersite and rhabdite samples are shown in Fig. 1. These spectra appeared to be quite different. Mössbauer spectrum of schreibersite is very complicate and may consist of at least several magnetic sextets and several quadrupole doublets. A small amount of kamacite was not re- moved from the sample and related to very weak left and right outside peaks. Mössbauer spectrum of rhabdite demonstrates the presence of unresolved magnetic splitting and possibly quadru- pole doublet. The unresolved magnetic splitting may be a result of the relaxation processes or fuzzy magnetic phase transition in the sample at room temperature as well as a result of superpara- magnetic behavior of small rhabdite particles. These results dem- onstrate the difference of the hyperfine interactions in schreiber- site and rhabdite related to its structure. However, further studies are required for detailed clarification.

a

b

Fig. 1. Mössbauer spectra of schreibersite (a) and rhabdite (b). T=295 K.