caa a22 4500 463217144 CHVBK 20180405153200.0 cr unu---uuuuu 170326e20071101xx s 000 0 eng 10.1007/s00269-007-0175-5 doi (NATIONALLICENCE)springer-10.1007/s00269-007-0175-5 An EPR and SQUID magnetometry study of bornite [Elektronische Daten] [M. Borgheresi, F. Di Benedetto, A. Caneschi, G. Pratesi, M. Romanelli, L. Sorace] A magnetic and spectroscopic characterisation has been performed on a natural bornite sample from the Natural History Museum of the University of Florence. The combination of magnetic measurements and continuous-wave electron paramagnetic resonance (cw-EPR) spectroscopy at different temperatures and frequencies provided information about the distribution and valence states of Cu and Fe in bornite. The studied sample was found to obey the Curie-Weiss law with a transition from a paramagnetic to an antiferromagnetic phase at 64K; its possible attribution to a disordered spin glass phase was ruled out by ac susceptibility measurements. Q- and X-band cw-EPR measurements confirmed the presence of Fe(III) as fundamental valence state in bornite: the single EPR line registered in the temperature range from 300 to 65K can be assigned, in fact, to the Fe(III) single ions. Some Cu(II) signals were revealed in the low temperature EPR spectra and attributed to an early stage of the surface alteration. The width of the Fe(III) EPR spectrum, which hinders any characteristic spectral structure, can be ascribed to the exchange interaction. The pure antiferromagnetic character of the magnetic transition confirms the ordering between Fe and Cu in the bornite structure, at least at low temperature (≤70K). Moreover, the relatively high Nèel temperature suggests the accepted model of Collins et al.'s (Can J Phys 59:535-539, 1981) to conveniently explain the overall magnetic properties in the range 298-4K. Despite the increasing of the susceptibility in the paramagnetic range, in fact, the integrated EPR line area decreases by lowering the temperature, thus suggesting a progressive rising of the antiferromagnetic interactions among next-nearest-neighbouring paramagnetic centres. Springer-Verlag, 2007 Bornite nationallicence EPR nationallicence SQUID magnetometry nationallicence Valence states nationallicence Magnetic order nationallicence Borgheresi M. Dipartimento di Scienze della Terra, Università di Firenze, Via G. La Pira 4, I50121, Firenze, Italy aut Di Benedetto F. Museo di Storia Naturale, Università di Firenze, Via G. La Pira 4, I50121, Firenze, Italy aut Caneschi A. Dipartimento di Chimica, Università di Firenze, Via della Lastruccia 3, I50019, Sesto Fiorentino, Italy aut Pratesi G. Dipartimento di Scienze della Terra, Università di Firenze, Via G. La Pira 4, I50121, Firenze, Italy aut Romanelli M. Dipartimento di Chimica, Università di Firenze, Via della Lastruccia 3, I50019, Sesto Fiorentino, Italy aut Sorace L. Dipartimento di Chimica, Università di Firenze, Via della Lastruccia 3, I50019, Sesto Fiorentino, Italy aut Physics and Chemistry of Minerals Springer-Verlag 34/9(2007-11-01), 609-619 0342-1791 34:9<609 2007 34 269 https://doi.org/10.1007/s00269-007-0175-5 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00269-007-0175-5 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Borgheresi M. Dipartimento di Scienze della Terra, Università di Firenze, Via G. La Pira 4, I50121, Firenze, Italy aut NATIONALLICENCE 700 1- Di Benedetto F. Museo di Storia Naturale, Università di Firenze, Via G. La Pira 4, I50121, Firenze, Italy aut NATIONALLICENCE 700 1- Caneschi A. Dipartimento di Chimica, Università di Firenze, Via della Lastruccia 3, I50019, Sesto Fiorentino, Italy aut NATIONALLICENCE 700 1- Pratesi G. Dipartimento di Scienze della Terra, Università di Firenze, Via G. La Pira 4, I50121, Firenze, Italy aut NATIONALLICENCE 700 1- Romanelli M. Dipartimento di Chimica, Università di Firenze, Via della Lastruccia 3, I50019, Sesto Fiorentino, Italy aut NATIONALLICENCE 700 1- Sorace L. Dipartimento di Chimica, Università di Firenze, Via della Lastruccia 3, I50019, Sesto Fiorentino, Italy aut NATIONALLICENCE 773 0- Physics and Chemistry of Minerals Springer-Verlag 34/9(2007-11-01), 609-619 0342-1791 34:9<609 2007 34 269 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer