Quantum critical scaling in quasi-one-dimensional YbFe5 P3

We report measurements of the low-temperature magnetization M and specific heat C as a function of temperature and magnetic field of the quasi-one-dimensional spin chain, heavy-fermion compound YbFe5P3, which resides close to a quantum critical point. The results are compared to the predictions of scaling laws obtained from a generalized free-energy function expected near an antiferromagnetic quantum critical point (AFQCP). The scaling behavior depends on the dimensionality d of the fluctuations, the coherence length exponent ν, and the dynamic exponent z. The free energy treats the magnetic field as a relevant renormalization group variable, which leads to a new exponent φ=νzh, where zh is a dynamic exponent expected in the presence of a magnetic field. When zh=z,T/H scaling is expected, as observed in several compounds close to a QCP; whereas in YbFe5P3, a T/H3/4 dependence of the scaling is observed. This dependence reflects the relationship zh=(4z/3) and a field exponent φ=4/3. A feature of the scaling law is that it restricts the possible values of the exponents to two cases for YbFe5P3: d=1, ν=1, z=1, and d=2, ν=1/2, z=2.