Competing magnetic interactions and magnetocaloric effect in Ho₅Sn₃

The rare-earth intermetallic compound Ho₅Sn₃demonstrates fascinating magnetic properties, which include temperature-driven multiple magnetic transitions and field-driven metamagnetism. We address the magnetic character of this exciting compound through a combined experimental and theoretical studies. Ho₅Sn₃orders antiferromagnetically below 28 K, and shows further spin reorientation transitions at 16 K and 12 K. We observe a sizable amount of low-temperature magnetocaloric effect (MEC) in Ho₅Sn₃with a maximum value of entropy change ΔS= -9.5 J Kg^-1 K^-1for an applied field ofH= 50 kOe at around 30 K. The field hysteresis is almost zero above 15 K where the MEC is important. Interestingly, ΔSis found to change its sign from positive to negative as the temperature is increased above about 8 K, which can be linked to the multiple spin reorientation transitions. The signature of the metamagnetism is visible in the ΔSversusHplot. The magnetic ground state, obtained from the density functional theory based calculation, is susceptible to the effective Coulomb interaction (U_eff) between electrons. Depending upon the value ofU_eff, the ground state can be ferromagnetic or antiferromagnetic. The compound shows large relaxation (14% change in magnetisation in 60 min) in the field cooled state with a logarithmic time variation, which may be connected to the competing magnetic correlations observed in our theoretical calculations. The competing magnetic ground states are equally evident from the small value of the paramagnetic Curie-Weiss temperature.