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Fe-57 Mossbauer spectroscopy and magnetic measurement studies of oxygen deficient LaFeAsO

IR@NPL: CSIR-National Physical Laboratory, New Delhi

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Title Fe-57 Mossbauer spectroscopy and magnetic measurement studies of oxygen deficient LaFeAsO
 
Creator Nowik, Israel
Felner, Israel
Awana, V. P. S.
Vajpayee, Arpita
Kishan, H.
 
Subject Physics
 
Description We report on the magnetic behavior of the oxygen deficient LaFeAsO1−x (x~0.10) compound, prepared by one-step synthesis, which crystallizes in the tetragonal (SG P4/nmm) structure at room temperature. Resistivity measurements show a strong anomaly near 150 K, which is ascribed to the spin density wave instability. On the other hand, dc magnetization data show paramagnetic-like features down to 5 K, with an effective moment of 0.83 µB/Fe. 57Fe Mössbauer studies (MS) have been performed at 95 and 200 K. The spectra at both temperatures are composed of two sub-spectra. At 200 K the major one (88%) is almost a singlet, and corresponds to those Fe nuclei which have two oxygen ions in their close vicinity. The minor one, with a large quadrupole splitting, corresponds to Fe nuclei which have vacancies in their immediate neighborhood. The spectrum at 95 K exhibits a broadened magnetic split major (84%) sub-spectrum and a very small magnetic splitting in the minor sub-spectrum. The relative intensities of the sub-spectra lead to estimating the actual amount of oxygen vacancies in the compound to be 7.0(5)%, instead of the nominal LaFeAsO0.90. These results, when compared with reported 57Fe MS of non-superconducting LaFeAsO and superconducting LaFeAsO0.9F0.1, confirm that the LaFeAsO0.93 studied is a superconductivity–magnetism crossover compound of the newly discovered Fe based superconducting family.
 
Publisher IOP Publishing
 
Date 2008-06
 
Type Article
PeerReviewed
 
Format application/pdf
 
Identifier http://npl.csircentral.net/1028/1/94.pdf
Nowik, Israel and Felner, Israel and Awana, V. P. S. and Vajpayee, Arpita and Kishan, H. (2008) Fe-57 Mossbauer spectroscopy and magnetic measurement studies of oxygen deficient LaFeAsO. Journal Of Physics: Condensed Matter, 20 (29). pp. 292201-1. ISSN 0953-8984
 
Relation http://iopscience.iop.org/0953-8984/20/29/292201/
http://npl.csircentral.net/1028/