Magnetic properties of the rare-earth aluminides RECo2Al8 (RE = La, Ce, Pr, Nd and Sm).

We present the magnetic, thermal and transport properties of single crystals of the RECo2Al8 (RE = La, Ce, Pr, Nd and Sm) rare-earth aluminides. The Ce-based material is characterized as a Kondo system and moderate heavy fermion, for which the Sommerfeld coefficient is about ten times that determined for the La-based material ( γ^Ce= 138 mJ/mol.K and γ^La = 14 mJ/mol.K, respectively). The Pr-, Nd- and Sm-based materials all present antiferromagnetic (AFM) order that develops below 4.93 K, 8.2 K and 21.4 K, respectively. In the cases of the Nd- and Sm-based materials, frustrated in plane AFM interactions are observed. For the Pr-based compound, indeed two consecutive AFM transitions are observed in heat capacity and magnetization measurements (at 4.77 K and 4.93 K). Supported by isothermal magnetization and heat capacity measurements, we construct the T vs. H phase diagrams for the Pr- and Nd- based materials. Metamagnetic transitions from the low field AFM phase to a high field FM phase are observed. The FM phase is suppressed at further higher fields. Resistivity measurements are compatible with metallic behavior.