Evolution from insulator (x=0.003) to metal (x=1) of the Eu2+ local environment in Ca1−xEuxB6
Abstract
The local environment of Eu2+ (4 f7, S=72) in Ca1-x Eux B6 (0.003≤x≤1.00) is studied by means of electron spin resonance (ESR). For x≲0.07 the resonances have Lorentzian line shape, indicating an insulating environment for the Eu2+ ions. For x≳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 Eu2+ 4f electrons. High field ESR measurements for x≳0.30 reveal narrower and anisotropic linewidths, which are attributed to magnetic polarons and Fermi surface effects, respectively. © 2005 American Institute of Physics.
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