Ferromagnetism in novel compounds of the R3Pt23Si11 series with heavy rare earth: Gd, Tb, Dy, Ho and Er

We have synthesized new compounds of the R3Pt23Si11 series with R=Gd, Tb, Dy, Ho and Er, and studied their magnetic and thermodynamic properties. X-ray powder diffraction characterization confirms that all these compounds crystallize in the same face-centered cubic structure, space group Fm3¯m, as Ce3Pt23Si11. They all present a ferromagnetic order at low temperatures. The Curie temperatures range between 42±1 K and 3.39±0.05 K for Gd3Pt23Si11 and Er3Pt23Si11 respectively. For all compounds the value of the spontaneous moment at 2 K is far below the value expected for the saturated moment of the R3+ ions, except for the Gd compound. The estimations of the magnetic entropy at TC remain smaller than the full entropy of the fundamental multiplet, Rln(2J+1). Both reductions, of the moment and of the magnetic entropy, are ascribed to the crystal field effects. In the paramagnetic phase the thermal variation of the suceptibilities follows a Curie-Weiss law with Curie constants in good agreement with the theoretical values.