Effect of spin fluctuations in magnetocaloric and magnetoresistance properties of Dy10Co20Si70 alloy

Systematic investigations on the structure, magnetic, thermodynamic, magnetocaloric and magnetoresistance (MR) properties of the arc melted Dy10Co20Si70 alloy are presented. The Dy10Co20Si70 alloy crystallizes in tetragonal BaNiSn3-type DyCoSi3 (space group - I4mm; No. 107) as a major phase and CaF2-type CoSi2 (space group -Fm-3m; No. 225) and C-type Si (space group - Fd-3m; No. 227) as minor phases. The title compound exhibits multiple magnetic transitions having antiferromagnetic ordering at temperatures, viz., T-1 - 10.8K, T-2 - 8.8K and T-3 - 3.3K. The magnetic and thermodynamic studies confirm these magnetic anomalies in the compound. The large value of maximum magnetic entropy change, - Delta S-M(Max) - 16.4 and 26.6 J/kg K for the field change Delta H of 50 and 90 kOe, respectively, observed in the compound is associated with field induced magnetic transitions. Asymmetric broadening of the magnetic entropy change peaks above the ordering temperatures resulting in significant refrigerant capacities of 361 and 868 J/kg for DH - 50 and 90 kOe, respectively, in the compound is due to the spin fluctuation effect. The sign reversal in MR measurements is attributed to the field induced antiferromagnetic to ferromagnetic transition. A large positive MR (42% in 90 kOe) is observed at 2 K. The H-2 dependence of both the magnetocaloric effect (MCE) and MR in the paramagnetic regime indicates the role of the applied magnetic field in suppressing the spin fluctuations. The large MCE and MR together with no thermal or magnetic hysteresis establish this new compound as an attractive multifunctional magnetic material.