Evolution from insulator (x=0.003) to metal (x=1) of the Eu2+ local environment in Ca1-xEuxB6 -: art. no. 10A924

The local environment of Eu2+ (4f(7) S=7/2) in Ca1-xEuxB6 (0.003 <= x <= 1.00) is studied by means of electron spin resonance (ESR). For x less than or similar to 0.07 the resonances have Lorentzian line shape, indicating an insulating environment for the Eu2+ ions. For x greater than or similar to 0.07, the lines broaden and become Dysonian in shape, suggesting a change to metallic environment for the EU2+, ions, anticipating the semimetallic character of EuB6. The broadening is attributed to a spin-flip scattering relaxation process due to the exchange interaction between conduction and Eu(2+)4f electrons. High field ESR measurements for x greater than or similar to 0.30 reveal narrower and anisotropic linewidths, which are attributed to magnetic polarons and Fermi surface effects, respectively. (c) 2005 American Institute of Physics.