Metamagnetism, Multiple Magnetic Transitions and Wide Temperature Range Magnetocaloric Effect in Dy6.5Co2Si2.5 Alloy

Abstract

We report the structure, magnetic, thermodynamic, transport, and magnetocaloric properties of Dy6.5Co2Si2.5 alloy. It shows that this alloy has been formed in three phases viz., Dy5Si3, Dy3Co2.2Si1.8, 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 Dy6.5Co2Si2.5 alloy promising not only for low-temperature magnetic refrigeration but also for fundamental study perspectives.