Effect of Ho addition on AC soft magnetic property, microstructure and magnetic domain of FeCoNi(CuAl)0.8Hox (x = 0–0.07) high-entropy alloys

Abstract

Abstract The FeCoNi(CuAl)0.8 high-entropy alloy (HEA) consists of both face-centered cubic (FCC) phase and body-centered cubic (BCC) phase which allows for a fine tuning of the magnetic properties by controlling the concentration, morphology, and distribution of each phase. In this work, we report the effect of Ho addition on the microstructure, magnetic domains, and alternating current (AC) magnetic properties. FeCoNi(CuAl)0.8Ho0.05 (x\xa0=\xa00.05) HEA exhibits the optimum AC magnetic property with the minimum AC coercivity, hysteresis loss, eddy current loss and total loss among samples studied at both 50\xa0Hz and 950\xa0Hz. Ho addition increases the volume fraction of BCC phase. SEM-EDX results show that Cu and Ho elements are aggregated together at boundaries in Ho-containing alloys. Magnetic domain structure shows that stripe domains are observed in FCC phase and BCC phase with different domain width. Finely spaced domain in BCC phase leads to low eddy current loss. No domain pattern at boundaries is observed indicating that boundaries can hinder motion of domain resulting in an increase of the energy loss. Our findings provide a valid approach toward optimizing the desired physical properties of HEA magnets by adding a small fraction of rare earth element.