Percolation limited magnetic order in Eu<Subscript>1-x</Subscript>Ca<Subscript>x</Subscript>B<Subscript>6</Subscript>

We report the results of measurements of the low-temperature specific heat C<Subscript>p</Subscript>(T) and the ac susceptibility χ<Subscript>ac</Subscript>(T) in low applied magnetic fields for a series of samples of Eu<Subscript>1-x</Subscript>Ca<Subscript>x</Subscript>B<Subscript>6</Subsc ript>. The anomalies in C<Subscript>p</Subscript>(T), together with the results for χ<Subscript>ac</Subscript>(T) and M(H), confirm the onset of phase transitions to long range magnetic order for x > 0.7 and provide evidence that for x ≥ 0.7, the Eu moments, which are captured in large magnetic clusters with magnetic moments of the order of 260 μ<Subscript>B</Subscript>, adopt a spin-glass type ground state. The data set allows to establish the low-temperature [ T,x] phase diagram of this alloy series. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2005