Magnetic and structural relationship of RFe₂Si₂ and R(Fe_1-xM_x)₂Si₂(x = 0-1) systems (R = La, y and Lu, M = Ni, Mn and Cu)

Due to the similarity between AFe2As2 (A = Ba, Sr) and RFe2Si2 (R = La, Y and Lu), the RFe2Si2 system has been proposed as a potential candidate for a new high TC superconducting family containing Fe-Si (instead of Fe-As) layers as a structural unit. Various R (Fe1-xMx)2 Si2 (M = Ni and Cu) materials were synthesized and measured for their magnetic properties. None of these materials is superconducting down to 1.8 K. A pronounced peak at 232 K was observed in the magnetization curve of YFe2Si2. ⁵⁷Fe Mössbauer studies confirm the absence of any long-range magnetic ordering below 232 K. Similar peaks at various temperatures also appear in R (Fe1-xMx)2 Si2 samples. For Y (Fe1-xMnx)2 Si2 the peak position is dramatically affected by the magnetic Mn dopants. Four independent factors affect the peak position and shift it to lower temperatures: (i) the lattice parameters, (ii) the concentration of x (iii) the applied magnetic field and (iv) the magnetic nature of M. It is proposed that the magnetic peaks observed in RFe2Si2 and in R (Fe1-xMx)2 Si2 represent a new nearly ferromagnetic Fermi liquid system, its nature is yet to be determined.