Effect of magnetic fields on the specific heat of a YBa2Cu3O7- single crystal near Tc

In a c-axis magnetic field, the specific-heat peak of a single crystal of YBa2Cu3O7- broadens and decreases in amplitude with little shift in position. The difference between the zero-field specific heat and that measured in a field is found to satisfy a scaling relation which suggests critical, as opposed to Gaussian, fluctuations. This is interpreted in terms of the broadening of the critical regime by the magnetic field, and suggests either renormalization of the critical exponents by disorder or an order parameter with more than two components.