Investigation of the electronic and structural properties of potassium hexaboride, KB6, by transport, magnetic susceptibility, EPR, and NMR measurements, temperature-dependent crystal structure determination, and electronic band structure calculations

A Ammar; M Ménétrier; A Villesuzanne; S Matar; B Chevalier; J Etourneau; G Villeneuve; J Rodríguez-Carvajal; H-J Koo; A I Smirnov; M-H Whangbo

doi:10.1021/ic049444c

Investigation of the electronic and structural properties of potassium hexaboride, KB6, by transport, magnetic susceptibility, EPR, and NMR measurements, temperature-dependent crystal structure determination, and electronic band structure calculations

Inorg Chem. 2004 Aug 9;43(16):4974-87. doi: 10.1021/ic049444c.

Authors

A Ammar¹, M Ménétrier, A Villesuzanne, S Matar, B Chevalier, J Etourneau, G Villeneuve, J Rodríguez-Carvajal, H-J Koo, A I Smirnov, M-H Whangbo

Affiliation

¹ Institut de Chimie de la Matière Condensée de Bordeaux, ICMCB-CNRS, 87 Avenue du Dr. A. Schweitzer, 33608 Pessac Cedex, France.

PMID: 15285674
DOI: 10.1021/ic049444c

Abstract

The electronic and structural properties of potassium hexaboride, KB(6), were examined by transport, magnetic susceptibility, EPR, and NMR measurements, temperature-dependent crystal structure determination, and electronic band structure calculations. The valence bands of KB(6) are partially empty, but the electrical resistivity of KB(6) reveals that it is not a normal metal. The magnetic susceptibility as well as EPR and NMR measurements show the presence of localized electrons in KB(6). The EPR spectra of KB(6) have two peaks, a broad ( approximately 320 G) and a narrow (less than approximately 27 G) line width, and the temperature-dependence of the magnetic susceptibility of KB(6) exhibits a strong hysteresis below 70 K. The temperature-dependent crystal structure determination of KB(6) shows the occurrence of an unusual variation in the unit cell parameter hence supporting that the hysteresis of the magnetic susceptibility is a bulk phenomenon. The line width DeltaH(pp) of the broad EPR signal is independent of temperature and EPR frequency. This finding indicates that the line broadening results from the dipole-dipole interaction, and the spins responsible for the broad EPR peak has the average distance of approximately 1.0 nm. To explain these apparently puzzling properties, we examined a probable mechanism of electron localization in KB(6) and its implications.