Double exchange between chromium ions in a KZnF3:Cr3 + ,Cr2 + crystal Eremin, M. V. ; Nikitin, S. I. ; Silkin, N. I. ; Tsvetkov, A. I. ; Yusupov, R. V. Abstract Publication: Soviet Journal of Experimental and Theoretical Physics Letters Pub Date: April 1995 Bibcode: 1995JETPL..61..612E