Neutron scattering, magnetometry, and muon spin rotation (μSR) measurements were performed to investigate the magnetic order and spin dynamics across the ferromagnet-to-paramagnet transition in the hole-doped Mott insulator Y1−xCaxTiO3. We find that the transition proceeds through a volume-wise phase separation into ferromagnetic and paramagnetic regions. Spin fluctuations with a characteristic timescale of ∼ 0.1 μs, as detected via μSR, are observed to appear at Ca concentrations x≥0.10. The magnetic phase separation, accompanied by a modest dynamic response, represents a novel behavior in Mott systems near the loss of magnetic order. It is linked to a previously observed insulator-metal transition and the associated electronic phase separation into hole-poor Mott insulating and hole-rich metallic phases for 0<x<0.50. In particular, the x-dependence of the paramagnetic volume fraction strongly correlates with that of the volume fraction of the hole-rich metallic phase. The spin-wave spectra reveal a doping-induced crossover from isotropic to two-dimensional anisotropic exchange interactions, reflecting substantial changes in the orbital state with increasing Ca content.
@article{arxiv.2502.12312,
title = {Nature of the ferromagnet-paramagnet transition in Y$_{1-x}$Ca$_{x}$TiO$_{3}$},
author = {S. Hameed and I. Khayr and J. Joe and G. Q. Zhao and Y. Cai and K. M. Kojima and S. Chi and T. J. Williams and M. Matsuda and Y. J. Uemura and M. Greven},
journal= {arXiv preprint arXiv:2502.12312},
year = {2025}
}