The influence of magnetic sublattice dilution on magnetic order in CeNiGe3 and UNiSi2

TL;DR

This study investigates how substituting non-magnetic Y and Th atoms affects the magnetic ordering in CeNiGe3 and UNiSi2, revealing a gradual suppression of magnetic order and transition to short-range magnetism with increased dilution.

Contribution

It provides detailed experimental insights into the effects of magnetic sublattice dilution on magnetic order in CeNiGe3 and UNiSi2, highlighting the evolution from long-range to short-range magnetic states.

Findings

Magnetic ordering temperatures decrease with increased dilution.

Long-range magnetic order transitions to short-range below critical concentrations.

Lattice parameters change linearly with doping levels.

Abstract

Polycrystalline samples of the Y-diluted antiferromagnet CeNiGe3 (T_N = 5.5 K) and Th-diluted ferromagnet UNiSi2 (T_C = 95 K) were studied by means of x-ray powder diffraction, magnetization and specific heat measurements performed in a wide temperature range. The lattice parameters of the Ce1-xYxNiGe3 alloys decrease linearly with increasing the Y content, while the unit cell volume of U1-xThxNiSi2 increases linearly with rising the Th content. The ordering temperatures of the systems decrease monotonically with increasing x down to about 1.2 K in Ce0.4Y0.6NiGe3 and 26 K in U0.3Th0.7NiSi2, forming a dome of a long-range magnetic order on their magnetic phase diagrams. The suppression of the magnetic order is associated with distinct broadening of the anomalies at T_N,C due to crystallographic disorder being a consequence of the alloying. Below the magnetic percolation threshold xc of about 0.68 and 0.75 in the Ce- and U-based alloys, respectively, the long-range magnetic order smoothly evolves into a short-range one, forming a tail on the magnetic phase diagrams. The observed behaviour Ce1-xYxNiGe3 and U1-xThxNiSi2 is characteristic of diluted magnetic alloys. (c) 2012 IOP Publishing Ltd.