Magnetic field study of the 'hidden transition' in UCd 11

The specific heat of U Cd11 was measured in magnetic fields to 27 T. Besides the antiferromagnetic transition, there is a second transition that can be clearly resolved in fields between 14 and 20 T. This second transition (at Tm) extrapolates to a broad shoulder in CT in zero field. The two lines of transitions cross somewhere between 20 and 23 T. Tm displays unusually weak dependence on the strength of the magnetic field. Our results argue for the intrinsic origin of this "hidden" transition. © 2005 American Institute of Physics.