Phase separation near the charge neutrality point in FeSe1-xTex crystals with x < 0.15

Abstract Our study of FeSe$ _ {1-x}$Te$ {x}$ crystals with x $&lt;$ 0.15 shows that the phase separation in these compositions occurs into phases a different stoichiometry iron. This may indicate structural instability iron plane studied range compositions. We tentatively propose an explanation layered compounds terms possible change bond polarity and peculiarity direct $d-d$ exchange framework basic phenomenological description such as Bethe-Slater curve. With this approach, when distance between atoms is close to value at which sign magnetic for some $d$ orbitals changes, electronic can occur. Anomalies crystal field near point charge neutrality also be significant component instability.