Remarkable magnetostructural coupling around the magnetic transition in CeCo$_{0.85}$Fe$_{0.15}$Si

TL;DR

This study reveals strong magnetostructural coupling in CeCo$_{0.85}$Fe$_{0.15}$Si, showing how magnetic and lattice properties interact around the magnetic transition, with notable effects under high magnetic fields.

Contribution

It provides a detailed experimental analysis of the magnetostructural effects and coupling in CeCo$_{0.85}$Fe$_{0.15}$Si, highlighting the role of lattice effects in magnetic ordering.

Findings

Thermal expansion shows a prominent peak at a temperature above the magnetic transition.

High magnetic fields suppress the resistivity tail but enhance the thermal expansion peak.

Significant and irreversible magnetostriction indicates strong lattice-magnetic interaction.

Abstract

We report a detailed study of the magnetic properties of CeCo$_{0.85}$Fe$_{0.15}$Si under high magnetic fields (up to 16 Tesla) measuring different physical properties such as specific heat, magnetization, electrical resistivity, thermal expansion and magnetostriction. CeCo$_{0.85}$Fe$_{0.15}$Si becomes antiferromagnetic at $T_N \approx$ 6.7 K. However, a broad tail (onset at $T_X \approx$ 13 K) in the specific heat precedes that second order transition. This tail is also observed in the temperature derivative of the resistivity. However, it is particularly noticeable in the thermal expansion coefficient where it takes the form of a large bump centered at $T_X$. A high magnetic field practically washes out that tail in the resistivity. But surprisingly, the bump in the thermal expansion becomes a well pronounced peak fully split from the magnetic transition at $T_N$. Concurrently, the magnetoresistance also switches from negative to positive just below $T_X$. The magnetostriction is considerable and irreversible at low temperature ($\frac {\Delta L}{L} \left(16 T\right) \sim$ 4$\times$10$^{-4}$ at 2 K) when the magnetic interactions dominate. A broad jump in the field dependence of the magnetostriction observed at low $T$ may be the signature of a weak ongoing metamagnetic transition. Taking altogether, the results indicate the importance of the lattice effects in the development of the magnetic order in these alloys.