Weak ferromagnetism and ferroelectricity in K 3 Fe 5 F 15

Here, we report on the observation of a weak ferromagnetic transition at T N = 122 K in a K 3 Fe 5 F 15 system which is ferroelectric and ferroelastic below T c = 490 K . The magnetization and the susceptibility continuously increase with decreasing T down to 2 K . The Mössbauer spectra show a spontaneous magnetic ordering and at least three sites corresponding to Fe 2 + and Fe 3 + . The ratio between Fe 2 + and Fe 3 + is 60:40. At 6 K , there are two magnetically ordered sextets with internal fields of 585 and 263 kOe . The "slim" hysteresis loops observed are as well characteristic of weak ferromagnetism. At 122 K and at low frequencies, the system shows dielectric anomaly characteristic of magnetoelectric behavior.