Structural, magnetic and thermal properties of the substitution series Ce$_2$(Pd$_{1-x}$Ni$_x$)$_2$Sn

TL;DR

This study investigates how substituting Pd with Ni in Ce$_2$(Pd$_{1-x}$Ni$_x$)$_2$Sn alters its structural, magnetic, and thermal properties, revealing a structural transition, increased Kondo temperature, and emergent magnetic behavior.

Contribution

It provides new insights into the effects of Ni substitution on the structure and magnetic properties of Ce$_2$(Pd$_{1-x}$Ni$_x$)$_2$Sn, including a structural phase change and changes in Kondo behavior.

Findings

Structural transition from tetragonal to orthorhombic at x=0.4

Merging of magnetic transitions at x=0.25

Emergence of weak magnetism in Ni-rich compositions

Abstract

Structural, magnetization and heat capacity studies were performed on Ce$_2$(Pd$_{1-x}$Ni$_x$)$_2$Sn ($0 \leq x \leq 1$) alloys. The substitution of Pd atoms by isoelectronic Ni leads to a change in the crystallographic structure from tetragonal (for $x \leq 0.3$) to centered orthorhombic lattice (for $x \geq 0.4$). The volume contraction thorough the series is comparable to the expected from the atomic size ratio between transition metal components. The consequent weak increase of the Kondo temperature drives the two transitions observed in Ce$_2$Pd$_2$Sn to merge at $x = 0.25$. After about a 1% of volume collapse at the structural modification, the system behaves as a weakly magnetic heavy fermion with an enhanced degenerate ground state. Notably, an incipient magnetic transition arises on the Ni-rich size. This unexpected behavior is discussed in terms of an enhancement of the density of states driven by the increase of the $4f$-conduction band hybridization and the incipient contribution of the first excited crystal field doublet on the ground state properties.