Browsing by Author "Manuel, P."
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Item Competing charge and magnetic order in the candidate centrosymmetric skyrmion host ${\mathrm{EuGa}}_{2}{\mathrm{Al}}_{2}$(American Physical Society, 2023) Vibhakar, A. M.; Khalyavin, D. D.; Moya, J. M.; Manuel, P.; Orlandi, F.; Lei, S.; Morosan, E.; Bombardi, A.Eu(Ga1−xAlx)4 are centrosymmetric systems that have recently been identified as candidates to stabilize topologically nontrivial magnetic phases, such as skyrmion lattices. In this Letter, we present a high-resolution resonant x-ray and neutron scattering study on EuGa2Al2 that provides new details of the complex coupling between the electronic ordering phenomena. Our results unambiguously demonstrate that the system orders to form a spin density wave with moments aligned perpendicular to the direction of the propagation vector below 19.5 K, and upon further cooling below 15 K, a cycloid with moments in the ab plane, in contrast to what has been reported in the literature. We show that concomitant with the onset of the spin density wave is the suppression of the charge density wave order, indicative of a coupling between the localized 4f electrons and itinerant electron density. Furthermore, we demonstrate that the charge density wave order breaks the fourfold symmetry present in the I4/mmm crystal structure, thus declassifying these systems as square-net magnets.Item Field-induced long-range magnetic order in the spin-singlet ground-state system YbAl3C3: Neutron diffraction study(American Physical Society, 2013) Khalyavin, D.D.; Adroja, D.T.; Manuel, P.; Daoud-Aladine, A.; Kosaka, M.; Kondo, K.; McEwen, K.A.; Pixley, J.H.; Si, QimiaoThe 4f-electron system YbAl3C3 with a nonmagnetic spin-dimer ground state has been studied by neutron diffraction in an applied magnetic field. A long-range magnetic order involving both ferromagnetic and antiferromagnetic components has been revealed above the critical field HC∼6 T at temperature T=0.05 K. The magnetic structure indicates that the geometrical frustration of the prototype hexagonal lattice is not fully relieved in the low-temperature orthorhombic phase. The suppression of magnetic ordering by the remanent frustration is the key factor stabilizing the nonmagnetic singlet ground state in zero field. Temperature-dependent measurements in the applied field H=12 T revealed that the long-range ordering persists up to temperatures significantly higher than the spin gap, indicating that this phase is not directly related to the singlet-triplet excitation. Combining our neutron diffraction results with the previously published phase diagram, we support the existence of an intermediate disordered phase as the first excitation from the nonmagnetic singlet ground state. Based on our results, we propose YbAl3C3 as a material for studying the quantum phase transitions of heavy-fermion metals under the influence of geometrical frustration.