Tri-critical point and suppression of the Shastry-Sutherland phase in Ce$_{2}$Pd$_{2}$Sn by Ni doping

TL;DR

This study investigates how Ni doping in Ce$_2$Pd$_2$Sn alters magnetic phases, leading to a tri-critical point where antiferromagnetic order is suppressed, revealing the interplay of Kondo screening, disorder, and magnetic interactions.

Contribution

It demonstrates the suppression of the Shastry-Sutherland phase and the emergence of a tri-critical point in Ce$_2$Pd$_2$Sn with Ni doping, highlighting the effects of disorder and Kondo screening.

Findings

The antiferromagnetic transition temperature decreases with Ni doping.

A tri-critical point occurs at x≈0.3 where AF phase is suppressed.

Ferromagnetic transition temperature increases with Ni doping.

Abstract

Structural, magnetization and heat capacity measurements were performed on Ce$_2$(Pd$_{1-x}$Ni$_x$)$_2$Sn ($0 \leq x \leq 0.25$) alloys, covering the full range of the Mo$_2$FeB$_2$ structure stability. In this system, the two transitions observed in Ce$_2$Pd$_2$Sn (at $T_N=4.8$\,K and $T_C=2.1$\,K respectively) converge into a tri-critical point at $T_{cr}\approx 3.4$\,K for $x\approx 0.3$, where the intermediate antiferromagnetic AF phase is suppressed. The $T_N(x)$ phase boundary decrease is due to an incipient Kondo screening of the Ce-4f moments and local atomic disorder in the alloy. Both mechanisms affect the formation of Ce-magnetic dimers on which the Shastry-Sutherland lattice (SSL) builds up. On the contrary, the $T_C(x)$ transition to the ferromagnetic ground state increases as a consequence of the weakening of the AF-SSL phase. Applied magnetic field also suppresses the AF phase like in the stoichiometric compound.