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Competing Ordered Phases inURu2Si2: Hydrostatic Pressure and Rhenium Substitution

“…Pressuredependent neutron scattering, NMR, and µSR measurements all indicate an abrupt increase in the size of the ordered moment, with the magnitude of the moment saturating to a value consistent with bulk AFM above a currently disputed critical pressure [23,24,25,26]. The interpretation of this increase in moment is currently unresolved, but can be divided into two prevailing descriptions: an inhomogeneous, phase separated scenario where the increase in the moment is due to an increase in volume fraction of the observed, high-pressure moment [25,26]; and a scenario involving two order parameters describing the staggered magnetization and the HO state, with the details governed by the coupling between order parameters [15,24].With the progression of experimental and theoretical investigations into the ordered states of URu 2 Si 2 , now is a critical time to clarify and categorize experimental observations in order to enhance the understanding of the underlying phenomena. The URu 2−x Re x Si 2 system provides a unique opportunity to study the effects of pressure on a HO state whose ambient pressure transition temperature is reduced with rhenium concentration x [27].…”

Hydrostaticity and hidden order: effects of experimental conditions on the temperature–pressure phase diagram of URu2Si2

“…While some neutron scattering reports concluded that the HO-AFM boundary is separate from the PM-HO/AFM curve [23,25], a more recent report of neutron scattering and ac susceptibility suggested a sharp transition at 7 kbar, consistent with HO-AFM phase separation [26,27], and supported a ∼ 4 kbar SC critical pressure. The latter phase diagram was recently corroborated by measurements of electrical resistivity and ac calorimetry [28].…”

“…While neutron scattering, NMR, and µSR probes are sensitive to the HO-AFM transition, in order to generate a full phase diagram, it has been necessary to also include the PM-HO/AFM transition determined from electrical resistivity data [19,23,25,26,27,38,40]. Conclusions made about the coupling between HO and AFM parameters depend upon extrapolations between these two curves, yet the resistivity data are rarely discussed beyond inclusion in the phase diagram.…”

“…Short of revisiting all published investigations performed using non-hydrostatic pressure media, in which the data may have been collected upon only pressurization or depressurization, the next best approach is to suggest the performance of these studies under controlled hydrostatic conditions. For example, because no moment was observed up to 5 kbar in neutron scattering experiment utilizing He [25], NMR and µSR measurements performed in He should also determine no AFM volume fraction below at least 5 kbar.…”

“…A survey of publications indicates that the following media have been used in studies of URu 2 Si 2 : helium [7,8,25], 1:1 n-pentane/isoamyl alcohol [11,14,19,32,33], transformer oil/kerosene [12,34,35,36], 1:1 FC70/FC77 [15,16,17,20,21,22,25,26,27,34,35,36,37,38], 4:1 methanol/ethanol [39], argon [28], and Daphne oil [38]. In some reports, the pressure medium was not disclosed [9,10,13,18,23,29,31,40,30].…”