Effect of transition-metal substitutions on competing electronic transitions in the heavy-electron compoundURu2Si2

Abstract

The moderately heavy-electron compound URu&Si2 is known to exhibit two electronic phase transitions at low temperatures, one to an antiferromagnetically ordered state at TN =17.5 K followed by another to a superconducting state at T, -1.5 K. The shape of the specific-heat anomaly at TN, which is reminiscent of a second-order BCS-type mean-field transition, suggests the formation of a spin-or charge-density wave opening a gap over part of the Fermi surface. The efFect of chemical substitution of the transition metals M =Re, Tc, Os, Rh, and Ir for Ru in URuzSi2 has been investigated by means of electrical resistivity, magnetic susceptibility, and specific-heat measurements in URu2 "M"Si2for x 0.2. The anomaly associated with the 17.5 K transition involves a very small magnetic entropy and is smeared out by very small concentrations of the M substituent. An inverse correlation between T, and TN in the Rhand Ir-doped materials for x &0.01 and in the Os-doped series for x & 0. 1 is consistent with the picture of two electronic transitions competing for states at the Fermi level.

Single Crystal Growth of URu2Si2 by the Modified Bridgman Technique

“…This is an important advance in crystal growth for these materials, because it provides an alternative way to produce single crystals that are needed for a variety of experiments: e.g., not only is it possible to cleave them, but their quality is also high enough to observe quantum oscillations, as seen in other specimens of similar quality [16,17]. Furthermore, previous studies of URu 2 Si 2 have benefitted from investigation of chemical substitution series [16,[18][19][20][21][22][23]. Most such work has focused on the substitution of elements with low vapor pressures that are easily dissolved in a stoichiometric melt.…”

The suppression of hidden order and the onset of ferromagnetism in URu2Si2via Re substitution

“…In contrast, substitution for Si has no dramatic effects [3]. Most of the neighboring elements of Ru: Mn, Tc, Th, Re, Os, Rh, and Ir have been substituted onto the Ru site, and in all cases except Os, the HO transition is suppressed by about 5% substituent concentration [4,5,6].…”

“…In contrast, substitution for Si has no dramatic effects [3]. Most of the neighboring elements of Ru: Mn, Tc, Th, Re, Os, Rh, and Ir have been substituted onto the Ru site, and in all cases except Os, the HO transition is suppressed by about 5% substituent concentration [4,5,6].For a few elements, the phase diagrams at higher concentrations have been studied. In the Rh case, in addition to the HO phase, there are two other nominally antiferromagnetic (AFM) phases, which are separated by nonmagnetic regions [7].…”

Non-Fermi Liquid Regimes and Superconductivity in the Low Temperature Phase Diagrams of Strongly Correlated d- and f-Electron Materials

“…Chemical substitution, particularly on the Ru site (URu 2−x M x Si 2 for transition metal M), also has yielded very rich physics [111,112]. The HO phase is typically suppressed by about x = 0.1 (5%), while at higher substituent concentration, long range magnetism emerges.…”