The 4f-electron system YbAl3C3 with a non-magnetic 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∼ 6T at temperature T=0.05K. 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 non-magnetic singlet ground state in zero field. Temperature dependent measurements in the applied field H=12T 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 non-magnetic singlet ground state. Based on our results, we propose YbAl3C3 as a new material for studying the quantum phase transitions of heavy-fermion metals under the influence of geometrical frustration.
@article{arxiv.1302.2245,
title = {Field-induced long-range magnetic order in the spin-singlet ground state system YbAl3C3: Neutron diffraction study},
author = {D. D. Khalyavin and D. T. Adroja and P. Manuel and A. Daoud-Aladine and M. Kosaka and K. Kondo and K. A. McEwen and J. H. Pixley and Qimiao Si},
journal= {arXiv preprint arXiv:1302.2245},
year = {2015}
}