Critical Behavior of the Heisenberg Ferromagnets EuO and EuS

Abstract

Neutron-scattering measurements have been made of the critical parameters of the simple Heisenberg ferromagnets EuO and EuS. Values of the critical exponents $\ensuremath{\beta}$ and $\ensuremath{\nu}$ and the amplitudes of $B$ and $F$ describing, respectively, the reduced magnetization and the inverse correlation range (above ${T}_{c}$) are in good accord with theory. The measured values of the exponent $\ensuremath{\gamma}$, describing the static susceptibility, support the recent prediction that $\ensuremath{\gamma}\ensuremath{\approx}1.40$ in a simple nearest-neighbor Heisenberg ferromagnet. The scaling relation between $\ensuremath{\beta}$, $\ensuremath{\nu}$, and $\ensuremath{\gamma}$ is fulfilled.