Fig. 4

Comparison of surface relaxation with bulk α and β relaxations. The magenta and purple curves along with the open circles show the bulk α and β relaxation rates vs. T_g/T in MGs³⁵, respectively. The solid square, star, and circle show the surface relaxation rate Γ_surface vs. T_g/T_sub estimated from vapor deposition of an ultrastable molecular glass⁵, the Zr-MG of ref. ¹⁰, and the sample studied in the present work, respectively. The rhombuses are for ethylcyclohexane glass as Γ_surface is the inverse critical free surface residence time at which the time of isothermal transformation from the glass into the supercooled liquid state reaches the plateau (Figure 9 in ref. ²¹). The Γ_surface from STM measurements are plotted as pentagons (left one: La₅₀Ni₁₅Al₂₅Cu₁₀, right one: La₆₀Ni₁₅Al₂₅ MGs³²) and as triangles (Fe₇₈B₁₃Si₉ MG^{33, 34}). The blue line is a linear fit to the surface relaxation rates