Defect-induced formation and frustration-driven multiple magnetic transitions in Gd2Co0.90Si2.90

Abstract

A new ternary compound, Gd₂Co_0.90Si_2.90, has been synthesized in a chemically single phase by deliberately introducing lattice vacancies in the Co and Si sites. The system is characterized by DC magnetization, heat capacity, resistivity and density functional theory (DFT) calculations. A detailed experimental study reveals that the system exhibits an antiferromagnetic transition below T_N = 11.3 K followed by spin freezing behaviour below T_B ∼ 4.8 K. An additional high-temperature magnetic transition could also be detected at T_H ∼ 150 K, which is short range in character and is associated with defect-induced polarization of the conduction electrons. The spin-glass-like state formation in the system is additionally bolstered by the observation of magnetic relaxation and associated aging phenomena as well as the magnetic memory effect. On the basis of non-equilibrium dynamical behaviour, we argue that the glassy state in this compound favours the hierarchical model over the droplet model. DFT calculations and experimental outcomes establish that the ground state is magnetically frustrated due to the small energy difference between distinct spin configurations having closely spaced ground-state energies.