We explore the magnetically ordered ground state of the isovalently substituted Mott insulator ${\mathrm{Y}}_{1-x}{\mathrm{La}}_x\mathrm{Ti}{\mathrm{O}}_3$ for $x\le$ 0.3 via single-crystal growth, magnetometry, neutron diffraction, x-ray magnetic circular dichroism, muon spin rotation, and small-angle neutron scattering (SANS). We find that the decrease in the magnetic transition temperature on approaching the ferromagnetic-antiferromagnetic 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 volumewise 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 increasing La substitution. We find no evidence for a spin-glass phase. Finally, from SANS and magnetometry measurements, we discern a crossover from easy-axis to easy-plane magnetocrystalline anisotropy with increasing La substitution. These results indicate complex changes in magnetic structure upon approaching the phase boundary.

• Received 15 February 2021
• Revised 26 April 2021
• Accepted 10 June 2021

DOI:https://doi.org/10.1103/PhysRevB.104.024410