High-Pressure Resistivity of YFe₂Si₂ and Magnetic Studies of Y_1−yHo _yFe₂Si₂ and YFe₂(Si_1−xGe _x)₂ Systems

High-pressure resistivity measurements (up to 18.8 kbar) indicate that YFe₂Si₂ is not superconducting (SC) down to 1.2 K. On the other hand, a clear magnetic peak is observed at 232 K. This peak was recently proposed to a new nearly ferromagnetic Fermi-liquid (NFFL) state. By chemical substitutions of magnetic Ho ions in the nonmagnetic Y site and/or C or Ge in the Si sites of YFe₂Si₂, we show that this peak is affected and shifted to lower temperatures by three factors: (i) lattice parameters caused by chemical substitution, (ii) applied magnetic field, and (iii) disorder induced by substitution in the Si sites. While Ho substitution does not change much the peak position, both isovalent C and Ge substitutions shift the peak to lower temperature, e.g., in YFe₂SiGe the peak position drops to 11 K, indicating that the dominant factor is the disorder induced in the Si site. None of investigated materials is SC down to 1.8 K. Apparently, in all compounds studied, the Fe ions are nonmagnetic, and it is assumed that all magnetic peaks reported here represent this new NFFL state previously proposed for YFe₂Si₂.