EuxSr1−xSySe1−y: A Model System for Studying Competing Magnetic Interactions

Abstract

The exchange-interaction parameters $J_1$ and $J_2$ determine the type of magnetic ordering in ${\mathrm{Eu}}_x{\mathrm{Sr}}_{1-x}{\mathrm{S}}_y{\mathrm{Se}}_{1-y}$. The ratio $\frac{J_2}{J_1}=-1\mathrm{}$, which holds at a concentration $y=0.1\mathrm{}$, appears as a critical point in the magnetic phase diagram. Close to this point mictomagnetism is observed in samples with Eu concentration high but lower than a critical value.