Double magnetic phase transitions and magnetotransport anomalies in a new compound Gd₂AgSi₃

Dc and ac–magnetic susceptibility (χ), specific heat (C_P), electrical resistivity (ρ) and magnetoresistance measurements performed on the new polycrystalline compound Gd₂AgSi₃, crystallizing in the α–ThSi₂ tetragonal structure, are reported. Two magnetic phase transitions were observed in dc and ac susceptibility, specific heat and resistivity measurements at temperatures T_N1=11 K and T_N2=20 K, despite a single site occupied by Gd atom, which is an indication of the complex magnetic behavior. Gd₂AgSi₃ turns out be one of the rare Gd compound in which a minimum is observed in the temperature dependence of resistivity in the paramagnetic state and also negative magnetoresistance over a wide temperature range (above T_N2), mimicking the behavior of exotic Gd₂PdSi₃, in this ternary family. The isothermal magnetic entropy change, adiabatic temperature change, and refrigerant capacity reach a value of 9.5 J/kg-K, 7.5 K and 302 J/kg, respectively for the change of magnetic field 0-9 T.