Neutron Scattering Study on Competition between Hidden Order and Antiferromagnetism in U(Ru_1-xRh_x)₂Si₂(x≤0.05)

Abstract

We have performed elastic and inelastic neutron scattering experiments on the solid solutions U(Ru1−xRhx)2Si2 for the Ru rich concentrations: x = 0, 0.01, 0.02, 0.025, 0.03, 0.04 and 0.05. Hidden order is suppressed with increasing x, and correspondingly the onset temperature Tm (∼ 17.5 K at x = 0) of weak antiferromagnetic (AF) Bragg reflection decreases. For x = 0.04 and 0.05, no magnetic order is detected in the investigated temperature range down to 1.4 K. In the middle range, 0.02 ≤ x ≤ 0.03, we found that the AF Bragg reflection is strongly enhanced. At x = 0.02, this takes place at ∼ 7.7 K (≡ TM), which is significantly lower than Tm (∼ 13.7 K). TM increases with increasing x, and seems to merge with Tm at x = 0.03. If the AF state is assumed to be homogeneous, the staggered moment µo estimated at 1.4 K increases from 0.02(2) µB/U (x = 0) to 0.24(1) µB/U (x = 0.02). The behavior is similar to that observed under hydrostatic pressure (µo increases to ∼ 0.25 µB/U at 1.0 GPa), suggesting that the AF evolution induced by Rh doping is due to an increase in the AF volume fraction. We also found that the magnetic excitation observed at Q = (1, 0, 0) below Tm disappears as T is lowered below TM.

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.…”

Phonon Thermal Transport ofURu2Si2: Broken Translational Symmetry and Strong-Coupling of the “Hidden Order” to the Lattice

“…and the thermal Hall conductivity, XY , are measured using the steady state method with two Cernox thermometers with an error of no more than 10%. U Ru 1ÿx Rh x 2 Si 2 crystals are grown using the Czochralski method [10], with x up to 0.04 (4%).Figure 1(a) shows T for tetragonal U Rh; Ru 2 Si 2 . All samples are measured with the heat current (Q) k c. URu 2 Si 2 displays a large upturn right at the HO transition.…”

Local suppression of the hidden-order phase by impurities in URu2Si2

“…At the critical doping x c the HO parameter vanishes and T ho (x c ) = 0; it follows that x c is given by for ∆ 1 = 358.6K with experimental data 18,30 . J ψ and ∆ 0 have been defined above for the uniform case and are equal to J ψ = 46.24K and ∆ 0 = 35K.…”

“…2. The emergence of a magnetic moment in URu 2 Si 2 doped with Rh has been observed also in neutron scattering experiments 30 . First, notice that the NMR and the neutron experiments are not completely compatible.…”

“…The presence of defects is required to explain the x = 0 experiment as stressed earlier in the pioneering work by Amitsuka 31 . The anisotropy of the droplets is required to account for the long correlation length in the ab plane observed by neutrons 30 . The abrupt change from x = 0.01 to x = 0.02 observed by neutrons could be due to the crossing of a percolation threshold of the AF droplets.…”