Effect of Vacuum Heat Treatment on Magnetic Ordering in Substituted Orthoferrite La_{1 – x}Sr_xFeO_{3 – δ}

The temperature dependences of the magnetization of La_{1 – x}Sr_xFeO_{3 – δ} samples (x = 0.33, 0.50, and 0.67) have been studied. Their Neel temperatures T_N have been determined, at which non-collinear antiferromagnetism (weak ferromagnetism) is settled down in the samples. The introduction of a substituting impurity of strontium into La_{1 – x}Sr_xFeO_{3 – δ} and an increase in its content results in a considerable decrease in T_N. This effect can be compensated using vacuum heat treatment, upon which, on the contrary, a noticeable increase in T_N is observed.