Possible Existence of Partially Disordered Sm Ions in Magnetically Ordered State of Ising Magnet SmPt2Si2: a Single Crystal Study

TL;DR

This study investigates the magnetic properties of SmPt2Si2, revealing partially disordered Sm ions and heavy quasiparticle formation, indicating complex magnetic frustration and Kondo effects in its ordered states.

Contribution

First detailed single crystal study showing coexistence of partial disorder and heavy quasiparticles in SmPt2Si2's magnetic phases.

Findings

Existence of partially disordered Sm ions in the antiferromagnetic phase.

Enhanced Sommerfeld coefficient indicating heavy quasiparticles.

Identification of two distinct magnetic phases, including a field-induced plateau.

Abstract

We have succeeded in growing single crystals of SmPt2Si2 and have performed electrical resistivity, magnetization and specific heat measurements. The magnetic susceptibility shows that SmPt2Si2 is an Ising magnet with the crystalline-electric-field ground state of Jz=+-3/2. We have found the existence of two magnetically ordered states, i.e., an antiferromagnetically (AFM) ordered phase (I) setting in at TN=5.1 K and a field-induced magnetization plateau phase (II). In the phase I, unlike the usual AFM states, a pronounced Curie-Weiss contribution remains in magnetic susceptibility, indicating the existence of "partially disordered" Sm ions. Largely enhanced Sommerfeld-coefficient (350 mJ/K2mol) in the phase I can be attributed to formation of Kondo sublattice with heavy quasiparticles in the partially disordered Sm ions. These findings may reflect substantial magnetic frustrations inherent in SmPt2Si2.