Magnetic contribution to the specific heat of Pb 1 − x Eu x Te ( x = 0.027 , 0.073 )

The temperature dependence of the magnetic specific heat has been studied experimentally and theoretically in the semimagnetic semiconductor ${\mathrm{Pb}}_{1\ensuremath{-}x}{\mathrm{Eu}}_{x}\mathrm{Te}$ for $x=0.027$ and 0.073, over the temperature range from 0.5 to $10\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, in magnetic fields up to $2\phantom{\rule{0.3em}{0ex}}\mathrm{T}$. There was a maximum in the magnetic specific heat between 1 and $3\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ even in zero and low magnetic fields; this maximum shifted toward higher temperatures with increasing magnetic field. The experimental data have been analyzed in the framework of a model in which we assume that the ground states of europium ions are split even without an external magnetic field. We present arguments which support this assumption and we show that it is possible to find a physical mechanism leading to the splitting which can explain the experimental results.