Anisotropic properties of Ba1−xSrxFe12O19 single crystals

Single crystals of Ba1−xSrxFe12O19 with x = 0, 0.25, 0.5, 0.75, and 1 were grown from a Na2CO3 flux. The obtained crystals were hexagon shaped plates with edge lengths of up to one centimetre and a thickness of several millimetres. Phase purity was confirmed by X-ray powder diffraction of crushed samples. The evolution of cell parameters a and c as a function of x in combination with thermal expansion measurements reveal a pronounced (thermo)mechanical anisotropy. Magnetic measurements show an additional strong magnetic anisotropy with the c-axis being the easy-axis, as typical for M-type hexaferrites. The absence of a detectable remanence or coercivity indicates the soft magnetization of the crystals. A small influence of x on the saturation moment was found as well as a linear increase of the Curie temperature with rising Sr-content in the entire x-range.