Complex interplay of 3d and 4f magnetism in La:GdMnO3

TL;DR

This study investigates how Gd doping influences the structural, magnetic, and electronic properties of LaMnO3, revealing complex magnetic interactions and phase transitions driven by 3d and 4f electron interplay.

Contribution

It provides detailed insights into the magnetic phase behavior and spin structures in Gd-doped LaMnO3, highlighting the interplay between 3d and 4f magnetism.

Findings

Gd doping suppresses magnetic transition temperatures.

Complex magnetic ordering occurs at low temperatures.

Magnetization shows compensation points and weak ferromagnetism.

Abstract

We report on structural, magnetic, electrical, and thermodynamic properties of Gd-doped LaMnO3 single crystals for Gd doping levels 0 <= x <= 1. At room temperature, for all doping levels the orthorhombic O' phase is indicative for a strong Jahn-Teller distortion. All compositions are insulating. The magnetism of La$_{1-x}$Gd$_x$MnO$_3$ is dominated by the relatively strong Mn-Mn exchange. The weakening of the antiferromagnetic interactions due to the significant decrease f the Mn-O-Mn bond angles leads to the continuous suppression of the magnetic phase-transition temperatures into the antiferromagnetic low-temperature phase for increasing Gd doping. The magnetization can only be explained assuming canting of the manganese spins. The magnetic moments of Gd are weakly antiferromagnetically coupled within the sublattice and are antiferromagnetically coupled to the Mn moments. For intermediate concentrations compensation points are found, below which the spontaneous magnetization becomes negative. In pure GdMnO3 the Mn spins undergo a transition into a complex, probably incommensurate magnetic structure at 41.5 K, followed by a further ordering transition at 16-20 K revealing weak ferromagnetism due to canting and finally by the onset of magnetic order in the Gd sublattice at 6.5 K. At the lowest temperatures and low external fields both magnetic sublattices reveal a canted structure with antiparallel ferromagnetic components.