Spin-glass behavior in YCo 10− xNi xSi 2 with high Ni content

Abstract

The magnetic properties and the structure of YCo 10− x Ni x Si 2 alloys with high Ni content have been investigated by means of measurements of X-ray diffraction, dc magnetization and ac-susceptibility. The samples are basically of single phase (with x=6, 7, 8, 8.5, 9, 10) and adopt the ThMn 12 type structure. With x≤7.0, the samples show ferromagnetic behavior below the Curie temperatures. For compounds YCo 2Ni 8Si 2 and YCo 1.5Ni 8.5Si 2, the ac-susceptibility and dc zero-field cooling (ZFC) M( T) curve show a cusp with decreasing temperature, and the dc ZFC and field cooling (FC) M( T) curves in lower fields exhibit thermal irreversibility at low temperatures. The magnetization curves at temperatures below the cusp temperature on the ZFC branches do not saturate in the field range of H≤55 kOe. Furthermore, the hysteresis loops at temperatures below the cusp temperature exhibit no coercivity after ZFC. All these features suggest a spin-glass ordering of the compounds YCo 10− x Ni x Si 2 with x equal to 8 and 8.5. The spin-glass behavior can be understood in terms of a competition between ferromagnetic interactions involving close Co–Co neighbors and antiferromagnetic interactions involving more remote Co–Co neighbors.