Nature of glassy magnetic state in magnetocaloric materials Dy5Pd2-xNix (x=0 and 1) and universal scaling analysis of R5Pd2 (R = Tb, Dy and Er)

We report a systematic investigation of the magnetic and magnetocaloric properties of Dy5Pd2 and Dy5PdNi. Our study on these compounds gave evidence that they exhibit complex magnetic behaviour along with the presence of glass-like magnetic phase. Furthermore, in these compounds both second order and first order phase transitions were present, which were validated through Arrott plots and Landau's parameter analysis. The ac susceptibility along with time dependent magnetization study has confirmed the presence of double cluster glass-like freezing in both Dy5Pd2 and Dy-5 PdNi. These compounds show a significant value of isothermal entropy change and relative cooling power and these values increased with Ni substitution. Beside conventional magnetocaloric effect, inverse magnetocaloric effect was noted in these compounds, which might arise due to the presence of complex non-equilibrium magnetic state. Along with these compounds a universal characteristic curve involving two other members of R5Pd2 family i.e. Er5Pd2 and Tb5Pd2 was constructed. The obtained universal curve also indicates presence of second order as well as first order magnetic phase transitions in these compounds. Additionally, magnetic entropy change followed the power law and the obtained exponent values indicated the presence of mixed magnetic interactions in these compounds. (C) 2018 Elsevier B.V. All rights reserved.