Figure 3

(a) M–H curves, and (b) variations of M_25kOe and H_c of Sr_0.75−xLa_0.25Ca_xFe_11.8Co_0.2O₁₉ hexaferrite (0.00 ≤ x ≤ 0.60) with respect to Ca content (x), obtained under the applied field of 25 kOe at room temperature. The enlarged views in (a) clearly show the M–H loops.