Low-temperature antiferromagnetic order in orthorhombic CePdAl_{3}

Abstract

We report the magnetization, ac susceptibility, and specific heat of optically float-zoned single crystals of CePdAl_{3}. In comparison to the properties of polycrystalline CePdAl_{3} reported in the literature, which displays a tetragonal crystal structure and no long-range magnetic order, our single crystals exhibit an orthorhombic structure (Cmcm) and antiferromagnetic order below a Néel temperature T_{1}=5.6 K. The specific heat at zero field shows two anomalies, namely, a broad transition at T_{1}=5.6 K followed by a λ-anomaly at T_{2}=5.4 K. A conservative estimate of the Sommerfeld coefficient of the electronic specific heat, γ=121mJK^{−2}mol^{−1}, indicates a moderately enhanced heavy-fermion ground state. A twin microstructure evolves in the family of planes spanned by the basal plane lattice vectors a_{o} and c_{o}, with the magnetic hard axis b_{o} common to all twins. The antiferromagnetic state is characterized by a strong a_{o}, c_{o} easy-plane magnetic anisotropy where the a_{o} direction is the easy axis in the easy plane. A spin-flop transition induced under magnetic field along the easy directions, results in complex magnetic phase diagrams. Taken together, our results reveal a high sensitivity of the magnetic and electronic properties of CePdAl_{3} to its structural modifications.