Growth and characterization of large (Y,La)TiO$_3$ and (Y,Ca)TiO$_3$ single crystals

TL;DR

This study reports on the growth and detailed characterization of large single crystals of (Y,La)TiO$_3$ and (Y,Ca)TiO$_3$, addressing challenges like overoxidation and exploring their magnetic and electronic properties.

Contribution

It introduces successful growth techniques for these titanates and provides comprehensive physical property analysis, including neutron scattering and spectroscopy, to understand overoxidation effects.

Findings

Successful growth of large single crystals using floating-zone technique.

Identification of TiO impurity phase in highly Ca-doped samples.

Detailed magnetic and electronic property characterization.

Abstract

The Mott-insulating rare-earth titanates (RTiO$_3$, R being a rare-earth ion) are an important class of materials that encompasses interesting spin-orbital phases as well as ferromagnet-antiferromagnet and insulator-metal transitions. The growth of these materials has been plagued by difficulties related to overoxidation, which arises from a strong tendency of Ti$^{3+}$ to oxidize to Ti$^{4+}$. We describe our efforts to grow sizable single crystals of YTiO$_3$ and its La-substituted and Ca-doped variants with the optical travelling-solvent floating-zone technique. We present sample characterization $via$ chemical composition analysis, magnetometry, charge transport, neutron scattering, x-ray absorption spectroscopy and x-ray magnetic circular dichroism to understand macroscopic physical property variations associated with overoxidation. Furthermore, we demonstrate a good signal-to-noise ratio in inelastic magnetic neutron scattering measurements of spin-wave excitations. A superconducting impurity phase, found to appear in Ca-doped samples at high doping levels, is identified as TiO.