High-Resolution Thermal Expansion of MgB2

TL;DR

This study measures the thermal expansion of MgB2 from 5 to 300 K, revealing a jump at Tc and a low-temperature peak, with no signs of structural instability, using high-resolution dilatometry.

Contribution

It provides detailed high-resolution measurements of MgB2's thermal expansion across a wide temperature range, confirming theoretical expectations and revealing subtle features.

Findings

Thermal expansivity shows a small jump at Tc.

A negative peak occurs near 5 K.

No structural instabilities are observed.

Abstract

The thermal expansion of polycrystalline MgB2 from 5-300 K is studied using high-resolution capacitance dilatometry. The thermal expansivity exhibits a small jump of -5.8x10-8 K-1 at Tc (in accord with expectations from the Ehrenfest relationship and published specific heat and pressure data) and a negative peak-like feature close to 5 K. No indications of any structural instabilities are observed.