Metamagnetism, Multiple Magnetic Transitions and Wide Temperature Range Magnetocaloric Effect in Dy_6.5Co₂Si_2.5 Alloy

We report the structure, magnetic, thermodynamic, transport, and magnetocaloric properties of Dy_6.5Co₂Si_2.5 alloy. It shows that this alloy has been formed in three phases viz., Dy₅Si₃, Dy₃Co_2.2Si_1.8, and Dy₃Co with four successive magnetic transitions named as T₁, T₂, T₃,T₄, at 43, 74.7, 90.5, and 132.4 K, respectively. The magnetic measurements display competing ferromagnetic and antiferromagnetic interactions in the alloy. At 2.5 K, the alloy exhibits hard ferromagnetic properties with a coercive field of 0.8 T. Metamagnetism is also evidenced in the isothermal magnetization measurements. The Arrot plot shows that this material undergoes first-order magnetic transitions below 47 K, and above which, magnetic transitions are of second order. The four successive magnetic transitions together with competing magnetic interactions give rise to a broadened magnetocaloric effect (MCE) peak with temperature width of ΔT = 83.8 and 93.2 K and consequently a large RC value of 474 and 739 J/kg, for a magnetic field change of 0–5 and 0–7 T, respectively. Additionally, it is found that the alloy exhibits negative magnetoresistance and attains a value of − 11 and − 7% at 2.5 and 50 K, respectively, in applied magnetic field of 9 T. Thus, the peculiar magnetic and magnetocaloric properties make the Dy_6.5Co₂Si_2.5 alloy promising not only for low-temperature magnetic refrigeration but also for fundamental study perspectives.