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

Due to the similarity between AFe(2)As(2) (A = Ba, Sr) and RFe2Si2 (R = La, Y and Lu), the RFe2Si2 system has been proposed as a potential candidate for a new high T-C superconducting family containing Fe-Si (instead of Fe-As) layers as a structural unit. Various R (Fe1-xMx)(2) Si-2 (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. Fe-57 Mossbauer 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) Si-2 samples. For Y(Fe1-xMnx)(2) Si-2 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) Si-2 represent a new nearly ferromagnetic Fermi liquid system, its nature is yet to be determined.