Solution growth of Ce–Pd–In single crystals: Characterization of the heavy-fermion superconductor Ce2PdIn8

Abstract

Solution growth of single crystals of the recently reported new compound Ce 2 PdIn 8 was investigated. When growing from a stoichiometry in a range 2:1:20 -2:1:35, single crystals of CeIn 3 covered by a thin (~50 μm) single-crystalline layer of Ce 2 PdIn 8 were mostly obtained. Using palladium richer compositions the thickness of the Ce 2 PdIn 8 layers were increased, which allowed mechanical extraction of single-phase slabs of the desired compound suitable for a thorough study of magnetism and superconductivity. In some solution growth products also CePd 3 In 6 (LaNi 3 In 6 -type of structure) and traces of phases with the stoichiometry CePd 2 In 7 , Ce 1.5 Pd 1.5 In 7 (determined only by EDX) have been identified. Magnetic measurements of the Ce 2 PdIn 8 single crystals reveal paramagnetic behaviour of the Ce 3+ ions with significant magnetocrystalline anisotropy. Above 70 K the magnetic susceptibility follows the Curie-Weiss law with considerably different values of the paramagnetic Curie temperature, for the magnetic field applied along the a-(-90 K) and c-(-50 K) axis. Below the reported critical temperature for superconductivity T c (0.69 K) the electrical resistivity drops to zero. Comparative measurements of the electrical resistivity, heat capacity and AC susceptibility of several crystals reveal that the superconducting transition is strongly sample-dependent. IntroductionIn some Ce-based compounds, the interaction of the Ce ions with the conduction electrons often leads to a large enhancement of the effective electron mass. These socalled heavy-fermion (HF) compounds exhibit attractive electronic properties, such as strongly enhanced paramagnetism, non-Fermi liquid behaviour, interplay between magnetism and superconductivity (SC), etc. During the last decade, the attention of many researchers has been focused on the series of HF materials of the general chemical formula Ce m T n In 3m+2n where m, n = 1 or 2 and T = Co, Rh, Ir. These compounds crystallize in the Ho m Co n Ga 3m+2n -type tetragonal structures with the space group P4/mmm. These structures are built by n layers of distorted cuboctahedra [CeIn 3 ] and one monolayer of rectangular parallelepipeds [TIn 2 ] stacked sequentially in the [001] direction [1] making the structure to be quasi-2D. The main building block of these compounds, the cubic CeIn 3 , is a heavy-fermion antiferromagnet (AF) with a Néel temperature T N = 10.2 K [2] and becomes superconducting (SC) under pressure [3]. The whole Ce m T n In 3m+2n series is characterized by interplay between magnetism and unconventional superconductivity, which makes these compounds suitable for thorough studies of varieties of the two cooperative phenomena in strongly correlated electron systems. The quasi-2D R m T n In 3m+2n crystal structure provides investigation of the effect of varying dimensionality on magnetism and unconventional superconductivity because

Coexistence of Antiferromagnetism and Superconductivity in Heavy Fermion Cerium Compound Ce3PdIn11

“…A remarkable close analogy is found between the SC properties of Ce 3 PdIn 11 and Ce 2 PdIn 8 . The SC transition temperature of our compound is T c  = 0.42 K while for Ce 2 PdIn 8 values between 0.45 and 0.7 K have been reported1314151632. In addition, the upper critical field yields B c2  = 2.3 T for Ce 3 PdIn 11 and 2.5 T for Ce 2 PdIn 8 which is very similar32.…”

“…The compound belongs to the Ce n T m In 3 n +2 m class of layered materials which comprises a numerous amount of compounds including CeCoIn 5 , CeRhIn 5 and Ce 2 RhIn 8  91011. Ce 3 PdIn 11 can be regarded as “intermediate step” between the cubic CeIn 3 which orders antiferromagnetically at T N  = 10.1 K12 and tetragonal Ce 2 PdIn 8 being a HF superconductor with T c between 0.45 and 0.7 K depending on the crystal quality13141516. It crystallizes in the typical tetragonal structure (space group P 4/ mmm ) based on the AuPt 3 -type (CeIn 3 -block) and PtHg 2 -type ( T in 2 ) units alternating along the [001]-direction as depicted in the Fig.…”

Quantum criticality near the upper critical field of Ce2PdIn8

“…For Ce 2 PdIn 8 , by contrast, the upper critical field is almost isotropic, in consistent with the much weaker anisotropy of the reported normal-state susceptibility. 29 Next, we turn to the signatures of NFL behavior in the normal state. As shown in Figure 5, for fields slightly above H c2 , a logarithmic divergence of the specific heat coefficient is found over more than one decade in T .…”

Fermi-surface topology of the heavy-fermion system Ce2PtIn8

“…Due to the novelty of Ce 2 PtIn 8 , there are, to the best of our knowledge, no publications addressing its ground state so far. However, the isostructural nonmagnetic compound Ce 2 PdIn 8 is known to become superconducting at T c = 0.7 K [24][25][26][27][28] . The same crystal structure is also realized in Ce 2 T In 8 with T = Co, Rh, Ir.…”