Issue
EPL
Volume 78, Number 2, April 2007
Article Number 27004
Number of page(s) 6
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
DOI http://dx.doi.org/10.1209/0295-5075/78/27004
Published online 29 March 2007
EPL, 78 (2007) 27004
DOI: 10.1209/0295-5075/78/27004

Valence values of the cations in selenospinel $\chem{Cu(Cr,Ti)_2Se_4}$

H.-J. Noh1, 2, 3, J.-S. Kang4, S. S. Lee4, G. Kim4, S.-W. Han2, S.-J. Oh2, J.-Y. Kim5, H.-G. Lee5, S. Yeo3, S. Guha3 and S.-W. Cheong3

1  Department of Physics, Chonnam National University - Gwangju 500-757, Korea
2  School of Physics & Center for Strongly Correlated Materials Research, Seoul National University - Seoul 151-742, Korea
3  Department of Physics & Astronomy and Rutgers Center for Emergent Materials - Piscataway, NJ 08854, USA
4  Department of Physics, The Catholic University of Korea - Puchon 420-743, Korea
5  Pohang Accelerator Laboratory, Pohang University of Science and Technology - Pohang 790-784, Korea

ffnhj@chonnam.ac.kr

received 18 January 2007; accepted in final form 4 March 2007; published April 2007
published online 29 March 2007

Abstract
A long-standing issue about the Cu valency in selenospinel CuCr2Se4 was investigated by soft X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD). Using the sensitivity of XAS and XMCD to the valence value of transition metal ion and its local symmetry, we checked the valence value of each cation in selenospinel CuCrxTi2-xSe4 (x= 1.0, 1.1, 1.5, and 2.0) and obtained spectroscopic evidence that a small amount of the Cu cation changes the valency from Cu(I) to Cu(II) as the Cr concentration increases from 1.0 to 2.0. Dependence of the Cu(II) concentration and the mean field magnetic exchange energy on the Cr concentration suggests the Cu d-hole could play a crucial role in the intriguing magnetic/electrical properties of CuCr2Se4.

PACS
71.20.Be - Transition metals and alloys.
78.70.Dm - X-ray absorption spectra.

© Europhysics Letters Association 2007