Weak ferromagnetism and ferroelectricity in $K3Fe5F15$ Available to Purchase

Here, we report on the observation of a weak ferromagnetic transition at $TN=122K$ in a $K3Fe5F15$ system which is ferroelectric and ferroelastic below $Tc=490K$⁠. The magnetization and the susceptibility continuously increase with decreasing $T$ down to $2K$⁠. The Mössbauer spectra show a spontaneous magnetic ordering and at least three sites corresponding to $Fe2+$ and $Fe3+$⁠. The ratio between $Fe2+$ and $Fe3+$ is 60:40. At $6K$⁠, there are two magnetically ordered sextets with internal fields of 585 and $263kOe$⁠. The “slim” hysteresis loops observed are as well characteristic of weak ferromagnetism. At $122K$ and at low frequencies, the system shows dielectric anomaly characteristic of magnetoelectric behavior.