Nature of the ferromagnetic-antiferromagnetic transition in Y$_{1-x}$La$_{x}$TiO$_{3}$

TL;DR

This study investigates the magnetic phase transition in Y$_{1-x}$La$_{x}$TiO$_{3}$, revealing a complex evolution from ferromagnetic to antiferromagnetic order with substitution, characterized by suppressed magnetic moments and a crossover in anisotropy.

Contribution

The paper provides a detailed experimental analysis of the magnetic transition in Y$_{1-x}$La$_{x}$TiO$_{3}$, highlighting the non-conventional nature of the phase transition and the magnetic anisotropy crossover.

Findings

Suppression of magnetic moments near the phase boundary.

Absence of typical second-order transition signatures.

Crossover from easy-axis to easy-plane anisotropy.

Abstract

We explore the magnetically-ordered ground state of the isovalently-substituted Mott-insulator Y$_{1-x}$La$_{x}$TiO$_{3}$ for $x$ $\leq$ 0.3 via single crystal growth, magnetometry, neutron diffraction, x-ray magnetic circular dichroism (XMCD), muon spin rotation ($\mu$SR) and small-angle neutron scattering (SANS). We find that the decrease in the magnetic transition temperature on approaching the ferromagnetic (FM) - antiferromagnetic (AFM) phase boundary at the La concentration $x_c$ $\approx$ 0.3 is accompanied by a strong suppression of both bulk and local ordered magnetic moments, along with a volume-wise separation into magnetically-ordered and paramagnetic regions. The thermal phase transition does not show conventional second-order behavior, since neither a clear signature of dynamic critical behavior nor a power-law divergence of the magnetic correlation length is found for the studied substitution range; this finding becomes increasingly obvious with substitution. Finally, from SANS and magnetometry measurements, we discern a crossover from easy-axis to easy-plane magneto-crystalline anisotropy with increasing La substitution. These results indicate complex changes in magnetic structure upon approaching the phase boundary.