Spin ordering and enhancement of electronic heat capacity in an organic system of (DI-DCNQI)(2)(Ag(1-x)Cu(x))

K Okuma; S Yamashita; Y Nakazawa; M Oguni; K Miyagawa; K Kanoda

doi:10.1088/0953-8984/21/1/015602

Spin ordering and enhancement of electronic heat capacity in an organic system of (DI-DCNQI)(2)(Ag(1-x)Cu(x))

J Phys Condens Matter. 2009 Jan 7;21(1):015602. doi: 10.1088/0953-8984/21/1/015602. Epub 2008 Dec 1.

Authors

K Okuma¹, S Yamashita, Y Nakazawa, M Oguni, K Miyagawa, K Kanoda

Affiliation

¹ Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan. Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, Meguro-Ku, Tokyo 152-8550, Japan.

PMID: 21817227
DOI: 10.1088/0953-8984/21/1/015602

Abstract

Thermodynamic measurements on the organic system of (DI-DCNQI)(2)(Ag(1-x)Cu(x)) (x = 0,0.05, 0.71, 0.90) were performed to study the change from the charge-ordered (CO) insulating state to the π-d hybridized metallic state. A thermal anomaly associated with the antiferromagnetic transition that occurred in the charge-ordered lattice was observed at 6.2 K from the temperature dependence of the heat capacity of (DI-DCNQI)(2)Ag. We have found that the magnetic entropy around the peak is only 1.5% of Rln2, corresponding to the full entropy expected for the formula unit of (DI-DCNQI)(2)Ag. This anomaly is suppressed down to about 3 K in the x = 0.05 sample owing to the disorders induced in the CO lattice. In the metallic concentration of x = 0.90, the low-temperature electronic heat capacity coefficient, γ was found to be enhanced by up to about 63.6 mJ K(-2) mol(-1) probably owing to the cooperative effect of π-d hybridization and intersite Coulomb interaction (V).