Itinerant antiferro- and ferro-magnetic instability in Re-doped URu2Si2: optical and point-contact spectroscopy results

We have conducted optical and point-contact spectroscopy (PCS) investigations on the URu2-xRexSi2(0 < x < 0.8) system, in order to determine the absorption spectrum and to obtain a fingerprint of the density of states with respect to the magnetic ground state as x is varied. In the antiferromagnetic phase (x < 0.1), we clearly have evidence for a gap-like feature in both the absorption and PCS spectra. On the other hand, these features disappear for the ferromagnetic ground state (x > 0.4). We discuss our experimental findings in relation to the itinerant nature of the magnetic phase transitions. (orig.)