  We report on zero-field muon spin rotation, electron spin resonance and
polarized Raman scattering measurements of the coupled quantum spin ladder
Ba2CuTeO6. Zero-field muon spin rotation and electron spin resonance probes
disclose a successive crossover from a paramagnetic through a spin-liquid-like
into a magnetically ordered state with decreasing temperature. More
significantly, the two-magnon Raman response obeys a T-linear scaling relation
in its peak energy, linewidth and intensity. This critical scaling behavior
presents an experimental signature of proximity to a quantum critical point
from an ordered side in Ba2CuTeO6.
