Heat flux measurements of Tb₃M series (M = Co, Rh and Ru): Specific heat and magnetocaloric properties

We report on the magnetic properties and magnetocaloric effect (MCE) for the Tb3M series, with M = Co, Rh and Ru, obtained using a heat flux technique. The specific heat of Tb3Co and Tb3Rh are very similar, with a first order type transition occurring around 6 K below the magnetic ordering temperature without any corresponding feature on the magnetization. The slightly enhanced electronic specific heat, the Debye temperature around 150 K and the presence of the magnetic specific heat well above the ordering temperature are also characteristic of many other compounds of the R3M family (R = Rare Earth). The specific heat for Tb3Ru, however, presents two peaks at 37 K and 74 K. The magnetization shows that below the first peak the system presents an antiferromagnetic behavior and is paramagnetic above 74 K. We obtained a magnetocaloric effect for M= Co and Rh, -Delta S=12 J/kg K, but for Tb3Ru it is less than 3 J/kg K (mu(0)Delta H = 5 T). We believe that the experimental results show that the MCE is directly related with the process of hybridization of the (R)5d-(M)d electrons that occurs in the R3M materials. (C) 2016 Elsevier B.V. All rights reserved