Synthesis, Magnetic and Electrical Characteristics of Ba‐Sr Hexaferrites Substituted with Samarium, Chromium and Aluminum

A series of M‐type Ba−Sr hexaferrites of composition Ba 0.20 Sr 0.80‐x Sm x Fe 12‐y (Cr 0.5 Al 0.5 ) y O 19 (x=0.00–0.40; y=0.00–0.32) were prepared by solid‐state reaction route. XRD patterns reveals that there is a single magnetoplumbite phase in the hexaferrites with the substitutiom of Sm (0.00≤x≤0.20) and CrAl (0.00≤y≤0.16) contents, while for the hexaferrites containing Sm (x≥0.30) and CrAl (y≥0.24), impurity phase is detected in the structure. The remanence ( B r ) decreases with increasing substitution content of Sm (0.00≤x≤0.40) and CrAl (0.00≤y≤0.32). With the increase of substitution contents, the intrinsic coercivity ( H cj ) increases, while the magnetic induction coercivity ( H cb ) first increases, and then decreases. B r has a linear decreasing behavior with increasing temperature from 20 °C to 170 °C. H cj raises linearly with increasing temperature from 20 °C to 170 °C. The average temperature coefficient of B r ( α B r ) basically remains constant with increasing substitution content of Sm (0.00≤x≤0.40) and CrAl (0.00≤y≤0.32). The average temperature coefficient of H cj ( α Hcj ) decreases with increasing substitution content of Sm (0.00≤x≤0.40) and CrAl (0.00≤y≤0.32). The electrical resitivity ( ρ ) decreases with increasing substitution content of Sm‐CrAl.