Magnetic susceptibility of an amorphous spin glass: Au-Si-Mn

Abstract

Amorphous films of ${\mathrm{Au}}_{0.81-x}{\mathrm{Mn}}_x{\mathrm{Si}}_{0.19}$ with $x=0.02, 0.05, \mathrm{and} 0.10$ were deposited at 77 K by getter-sputtering. The low-temperature ($T<\mathrm{}77\mathrm{}$ K) magnetic susceptibility ($\chi$) was measured on the as-deposited films and as a function of annealing. The susceptibility of the as-deposited film is about an order of magnitude lower than that reported for bulk ${\mathrm{Au}}_{0.95}$ ${\mathrm{Mn}}_{0.05}$, and the susceptibility peak is also much smaller [the ratio ($R=\frac{{\chi }_{max}}{\chi \left(4.2\mathrm{} \mathrm{K}\right)}$) is about 1.5 as compared to 4 for bulk]. Annealing the films at 293 K (which leaves the films amorphous) increases $\chi$ by a factor of 5 and $R$ to about 2. The most striking effect is observed after annealing at 373 K; the films are still mostly amorphous as determined by electrical resistivity, x-ray diffraction, and differential thermal analysis, but $R$ increases to values between 4 and 9. The reasons for this effect cannot be ascribed entirely to the presence of Si nor to partial recrystallization, since similar annealing effects were observed in crystalline ${\mathrm{Au}}_{0.95}$ ${\mathrm{Mn}}_{0.05}$ films.