# Giant In-Plane Shrinkage Induced by Structural Phase Transformation in TbCoSi2

## TL;DR

This paper explores TbCoSi2, a metal-based material that shrinks when cooled, offering potential for controlling thermal expansion in advanced applications.

## Contribution

The study reveals a 3% in-plane shrinkage in TbCoSi2 due to structural phase transitions, offering a new material for thermal expansion control.

## Key findings

- TbCoSi2 exhibits a 3% in-plane shrinkage from 223 K to 298 K due to structural phase transitions.
- The material adopts a Pbcm space group structure at low temperatures with significant a-axis shrinkage.
- Antiferromagnetic ordering occurs below 13.7 K, independent of structural transitions.

## Abstract

Metal-based materials, pivotal for industrialization and technological progress, confront the long-standing issue of high thermal expansion, which limits their application in advanced scenarios. With a century-long research history, negative thermal expansion materials, particularly those in intermetallic compounds, offer promising solutions for regulating thermal expansion. Here, we investigate polycrystalline TbCoSi2 ingots, revealing a notable 3% in-plane shrinkage from 223 K to 298 K induced by structural phase transitions. Temperature-dependent XRD and Rietveld refinement identify a low-temperature Pbcm space group structure, and the drastic a-axis shrinkage during the phase transition drives the in-plane contraction. Macroscopic magnetic measurements and first-principles calculations reveal an antiferromagnetic structure below 13.7 K, with magnetic and structural phase transitions being independent. These findings present a metal-based weakly magnetic material for precise thermal expansion control, particularly in the uniaxial direction.