Collinear Antiferromagnetic Order In Uru2si2-Xpx Revealed By Neutron Diffraction

The hidden order phase in URu2Si2 is highly sensitive to electronic doping. A special interest in silicon-to-phosphorus substitution is due to the fact that it may allow one, in part, to isolate the effects of tuning the chemical potential from the complexity of the correlated f and d electronic states. We investigate the new antiferromagnetic phase that is induced in URu2Si2-xPx at x greater than or similar to 0.27. Time-of-flight neutron diffraction of a single crystal (x = 0.28) reveals c-axis collinear q(m) = (1/2, 1/2, 1/2) magnetic order with localized magnetic moments (similar to 2.1-2.6 mu(B)). This points to an unexpected analogy between the (Si,P) and (Ru,Rh) substitution series. Through further comparisons with other tuning studies of URu2Si2, we are able to delineate the mechanisms by which silicon-to-phosphorus substitution affects the system. In particular, both the localization of itinerant 5 f electrons as well as the choice of q(m) appear to be consequences of the increase in chemical potential. Further, enhanced exchange interactions are induced by chemical pressure and lead to magnetic order, in which an increase in interlayer spacing may play a special