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)

TL;DR

This study explores the complex glassy magnetic behavior and magnetocaloric effects in Dy5Pd2 and Dy5PdNi, revealing both phase transitions and a universal scaling law across the R5Pd2 family.

Contribution

It provides new insights into the glass-like magnetic phases and the coexistence of first and second order transitions in Dy-based magnetocaloric materials, along with a universal scaling analysis.

Findings

Presence of glass-like magnetic phase confirmed by AC susceptibility and magnetisation studies.

Both first and second order phase transitions observed and validated through Arrott plots and Landau analysis.

Significant magnetocaloric effects with enhanced values upon Ni substitution, including inverse effects.

Abstract

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 parameter analysis. AC susceptibility along with time dependent magnetisation study has confirmed the presence of double cluster glass-like freezing in both Dy5Pd2 and Dy5PdNi. These compounds show 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 master curve reaffirmed the presence of both second and first order magnetic phase transition in such compounds which were in analogy to our results of Arrott plots and Landau parameter analysis. Additionally, magnetic entropy change followed the power law and the obtained exponent values indicated the presence of mixed magnetic interactions in these compounds.