Pressure versus magnetic-field tuning of a magnetic quantum phase transition

Specific heat $C(T)$ and electrical resistivity ρ(T) of CeCu_6-xAuₓ at very low temperatures T show distinctly different behavior depending on whether long-range antiferromagnetic order is suppressed by hydrostatic pressure p or an applied magnetic field B. p tuning yields C/T=aln(T₀/T) and ρ≈ρ₀+A^'T, while B tuning shows C/T=γ₀-a^'T0.5 and ρ≈ρ₀+A^''T1.5. This suggests that the spectrum of low-lying excitations that determines the behavior near these quantum phase transitions differs.