We have grown single crystals of ${\mathrm{La}}_{}$-substituted M-type strontium hexaferrites ${\mathrm{Sr}}_{1-x}{\mathrm{La}}_x{\mathrm{Fe}}_{12}{\mathrm{O}}_{19}$ using the traveling solvent floating zone technique, and investigated their magnetic and electrical properties. Although the saturation moment at room temperature increases monotonically with ${\mathrm{La}}_{}$ concentration $x$, its value at $5\mathrm{K}$ remains nearly constant up to $x=0.6$ and then slightly increases for higher $x$, suggesting that the magnetic moments at the minority spin sites tilt at low temperatures. At $5\mathrm{K}$, the shape of the magnetization curve exhibits qualitative changes at $x=1/3$ and $2/3$, which implies the formation of a triangular lattice of ${\mathrm{Fe}}^{2+}$ on the $2a$ sites. Our analysis of the magnetization curves at $5\mathrm{K}$ indicates that anisotropic exchange interactions between ${\mathrm{Fe}}^{2+}$ at the $2a$ sites enhance the anisotropy field for $x>1/3$. Furthermore, the temperature dependence of electrical resistivity suggests that the conduction mechanism changes around $150\mathrm{K}$, with the effects of localized ${\mathrm{Fe}}^{2+}$ ions being substantially reduced above this temperature.

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• Magnetic anisotropy
• Magnetic susceptibility
• Magnetism