POSSIBLE OBSERVATION OF A NEW MAGNETIC PHASE-TRANSITION IN USB

By measuring the polarization of neutrons transmitted through a USb single crystal we have discovered evidence for a second phase transition at T* = 142(2) K, about 70 K below TN ( = 213 K), in this well-studied antiferromagnetic actinide compound. The measurements show that a beam of polarized neutrons abruptly starts to become depolarized at T*. A number of other measurements find anomalies at T* and we propose that the transition is related to dephasing between the components of the triple-k structure known to exist in USb. This dynamic effect causes the formation of fluctuating domain walls containing ferromagnetic components, which then depolarize neutrons.