Role of band filling in tuning the high-field phases of URu2Si2

Abstract

We present a detailed study of the low temperature and high magnetic field phases in the chemical substitution series URu2Si2−xPx using electrical transport and magnetization in pulsed magnetic fields up to 65T. Within the hidden order x-regime (0 < x 0.035) the field induced ordering that was earlier seen for x = 0 is robust, even as the hidden order temperature is suppressed. Earlier work shows that for 0.035 x 0.26 there is a Kondo lattice with a no-ordered state that is replaced by antiferromagnetism for 0.26 x 0.5. We observe a simplified continuation of the field induced order in the no-order x-regime and an enhancement of the field induced order upon the destruction of the antiferromagnetism with magnetic field. These results closely resemble what is seen for URu2−xRhxSi2 a , from which we infer that charge tuning dominantly controls the ground state of URu2Si2, regardless of whether s/p or d-electrons are replaced. Contraction of the unit cell volume may also play a role at large x. This provides guidance for determining the specific factors that lead to hidden order versus magnetism in this family of materials and constrains possible models for hidden order.

Instability of the f -electron state in URu2Si2−xPx probed using high magnetic fields

“…In this work we report a detailed investigation of the magnetoresistivity of oriented single crystals of URu 2 Si 2−x P x . From the angular dependence of the magnetoresistivity, we find that the magnetic field induced phases (previously described in 30 ), display a 1/cos(θ) anisotropy is seen as for the parent compound. [31][32][33] Importantly, this includes x = 0.10 which is in the NO x-region.…”

Collinear antiferromagnetic order in URu2Si2−xPx revealed by neutron diffraction

“…Our measurements indicate c-axis collinear antiferromagnetic order with a propagation vector q m = ( 1 2 , 1 2 , 1 2 ) and an ordered moment of ∼2.1-2.6 μ B . This highlights that the phase diagrams of the two substitution series URu 2 Si 2−x P x [59][60][61][62] and URu 2−x Rh x Si 2 [45][46][47][48][49] are nearly identical with respect to the observed sequence of ground states. By comparison of various tuning studies, we infer that the localization of 5 f electrons as well as the selection of the q m = ( 1 2 , 1 2 , 1 2 ) order parameter is a common consequence of the increased chemical potential, whereas enhanced exchange interactions are induced by chemical pressure, in which the increase in interlayer spacing may play a special role.…”

“…Neutron diffraction or NMR measurements of URu 2 Si 2−x P x with x 0.26 as a function of magnetic field would be of great interest to confirm whether the high-field induced magnetic order in this system [62] is indeed the same as that found in the (Ru,Rh) series [49].…”

“…Here, we merely note that as in URu 2 Si 2−x P x , an antiferromagnetic state can be induced in the paramagnetic regime of URu 2−x Rh x Si 2 by applying a critical field of 26 T. A pulsedfield neutron diffraction study has shown that this magnetic order corresponds to a commensurate up-up-down ferrimagnetic structure with propagation vector q IN = ( 1 3 , 0, 0) [47,49]. Since the high-field magnetization of P and Rh substituted samples in the paramagnetic regime have very similar characteristics [62], and the magnetic order at higher P and Rh concentrations is identical, we speculate that the field-induced magnetic phase in URu 2 Si 2−x P x is also the one described by q IN . In summary, it is not straightforward to identify the mechanism of the large moment antiferromagnetic state discovered in URu 2 Si 2−x P x discovered at x 0.27, since the consequences of ionic substitution are necessarily entangled.…”

“…This is exemplified by a recent magnetoresistivity study under combined high pressures and magnetic fields that finds that the effects of both tuning parameters are intertwined [57]. To address this issue, the (Si,P) substitution series has been established [58][59][60][61][62], which is thought to weaken p-f hybridization [63], but affects the spacing and orientation of d-ligands only weakly. With the character of f -d interaction held intact, the donation of one p electron is thought to emphasize the effects of varying the chemical potential in the URu 2 Si 2 host.…”