Thickness and Temperature Dependent Out‐of‐Plane Anisotropy of Amorphous CoSiB Thin Films

Amorphous CoSiB thin films are prepared on Si (111) substrate at different temperatures. A thickness‐induced reversible spin reorientation transition (SRT) of the magnetic direction from in‐plane to out‐of‐plane is observed in the thick films due to the presence of out‐of‐plane anisotropy. Out‐of‐plane anisotropy is abnormally enhanced during the annealing process for films deposited at a low temperature, so the stress relaxation has no influence on out‐of‐plane anisotropy. The thermodynamic magnetization crossover effect from T3/2 to T2 occurs in the thick films due to the itinerant and localized characteristics of the 3d electrons of Co atoms. The temperature‐dependent SRT is found only in the 300‐nm‐thick film as the temperature increases from 5 to 400 K, whereas SRT has previously been shown to occur in the thick glassy films over a large thickness window. The thermodynamic magnetization crossover temperature shifts to a high temperature as the film thickness increases. As the film thickness decreases to 20 nm, the crossover effect disappears, and magnetization varies with temperature following the T2 law in the temperature range from 5 to 400 K. The low‐temperature SRT in the CoSiB alloy is due to the strong spin–orbit coupling, which is responsible for the low‐temperature out‐of‐plane anisotropy. The transition from low to high resistance provides evidence for the presence of localized 3d electrons in Co atoms. The thickness‐ and temperature‐dependent spin reorientation transition (SRT) in CoSiB amorphous thick thin films differs somewhat from previous reports. Experimental evidence obtained by Zhang et al. reveals that the short‐range order determines the formation of out‐of‐plane anisotropy, which is responsible for this unusual magnetic behavior. The low‐temperature SRT in the CoSiB alloy is due to the strong spin–orbit coupling at low temperature.