High Coercivity Ca-Al-Cr Tri-Substituted Strontium Ferrite Prepared by the Solid-Phase Method

Abstract

AbstractsIn this study, a series of bulk magnets with strontium ferrite Sr0.67Ca0.33Fe9Al3-xCrxO19 (x = 0.0, 0.5, 1.0, 1.5) were prepared using the solid-phase reaction method. The experimental results show that the structure of strontium ferrite is preserved even with a large amount of substitution when Ca replaces Sr and Al-Cr replaces Fe. Hysteresis loops show a high coercivity field at room temperature, and the highest coercivity Hc = 1.58 T is observed for the Sr0.67Ca0.33Fe9Al3-xCrxO19 (x = 0.0) magnets. They also have a coercivity temperature coefficient of 0.05%/°C below the room temperature, and even at 50k, its coercivity can reach up to 1.41 T. Meanwhile, the Al-substitute M-type strontium ferrite (Sr0.5Ca0.5Fe11.5Al0.5O19) is also investigated using the first-principle energy calculation method of density functional theory. Found preferential substitution of non-magnetic Al3+ for Fe3+ located at the 12k sites, which eliminates its positive contribution to the total magnetization strength, Al-substitute leads to a decrease in saturation magnetization. The structural observations are consistent with the experimental findings and provide insight into the relationship between the structure and magnetic properties of the substituted M-type strontium ferrite.

Keywords: Strontium ferrite, Solid-phase method, Coercivity, Al-Cr substitute