Quasi-two-dimensional ferromagnetism in the triangular magnet EuAl12O19

We report ferromagnetic ordering at $T_{\mathrm{C}}=1.3\mathrm{K}$ in the quasi-two-dimensional magnet ${\mathrm{EuAl}}_{12}{\mathrm{O}}_{19}$ with large spins $S=7/2$. This ferromagnetic state was characterized by magnetization and specific heat measurements and the experimental results were compared with classical Monte Carlo simulations. They reveal a strong single-ion anisotropy leading to a uniaxial spontaneous magnetization along the $c$ axis. Furthermore, the application of a magnetic field in the hard magnetization plane $ab$ reduces the Curie temperature down to $T=0.5\mathrm{K}$ at ${\mu }_{0}H\approx 0.4\mathrm{T}$ while preserving the second-order nature of the ferromagnetic transition.