Unusual giant magnetostriction in the ferrimagnet Gd$_{2/3}$Ca$_{1/3}$MnO$_3$

TL;DR

This paper reports an unusual giant linear magnetostrictive effect in Gd$_{2/3}$Ca$_{1/3}$MnO$_3$, highlighting the significant role of lanthanide 4f orbitals in magnetostriction, which challenges previous manganite models.

Contribution

It introduces a simple model explaining the magnetostriction behavior and emphasizes the importance of Gd 4f orbitals in magnetostriction phenomena in manganites.

Findings

Magnetostriction changes sign around 15 K.

Gd's 4f orbitals significantly influence magnetostriction.

A model balancing magnetic and elastic energies explains observations.

Abstract

We report an unusual giant linear magnetostrictive effect in the ferrimagnet Gd$_{2/3}$Ca$_{1/3}$MnO$_3$ ($T_{c} \approx$80 K). Remarkably, the magnetostriction, negative at high temperature ($T \approx T_{c}$), becomes positive below 15 K when the magnetization of the Gd sublattice overcomes the magnetization of the Mn sublattice. A rather simple model where the magnetic energy competes against the elastic energy gives a good account of the observed results and confirms that Gd plays a crucial role in this unusual observation. Unlike previous works in manganites where only striction associated with 3$d$ Mn orbitals is considered, our results show that the lanthanide 4$f$ orbitals related striction can be very important too and it cannot be disregarded.