Lock-in Behavior of the Partially Frustrated Order in CePdAl

CePdAl is one of the few systems that combines a metallic ground state with geometrical frustration. Its distorted kagome structure gives rise to an incommensurate antiferromagnetic order in which 1/3 of the Ce magnetic moments remain frustrated down to at least 20 mK. If this order is suppressed by hydrostatic pressure, unusual quantum criticality with spin-liquid properties emerges [1,2]. Surprisingly, the propagation vector of the partially frustrated antiferromagnetic phase exhibits a pronounced temperature dependence below its phase transition at TN ≈ 2.7 K in zero magnetic field. At temperatures below TL ≈ 1.9 K, the magnetic structure locks in to a propagation vector with still an incommensurate component along the c axis [3]. We use thermal expansion and magnetostriction measurements on a high-quality single crystal to track this lock-in transition to higher magnetic fields and construct the resulting magnetic phase diagram. The anisotropy of the uniaxial stress and strain dependences of TL are estimated. The nature of the lock-in transition is discussed in terms of geometrical frustration and glass transition physics.
[1] H. ... mehrZhao et al., Nature Physics 15, 1261 (2019)
[2] M. Majumder et al., arXiv:2202.11975 [cond-mat.str-el] (2022)
[3] L. Keller et al., Appl. Phys. A 74 [Suppl.], 686 (2002)