Strain-tunable metamagnetic critical endpoint in Mott insulating rare-earth titanates

Abstract

Rare-earth titanates are Mott insulators whose magnetic ground state -antiferromagnetic (AFM) or ferromagnetic (FM) -can be tuned by the radius of the rare-earth element. Here, we combine phenomenology and first-principles calculations to shed light on the generic magnetic phase diagram of a chemically-substituted titanate on the rare-earth site that interpolates between an AFM and a FM state. Octahedral rotations present in these perovskites cause the AFM order to acquire a small FM component -and vice-versa -removing any multi-critical point from the phase diagram. However, for a wide parameter range, a first-order metamagnetic transition line terminating at a critical end-point survives inside the magnetically ordered phase. Similarly to the liquid-gas transition, a Widom line emerges from the end-point, characterized by enhanced fluctuations. In contrast to metallic ferromagnets, this metamagnetic transition involves two symmetry-equivalent and insulating canted spin states. Moreover, instead of a magnetic field, we show that uniaxial strain can be used to tune this transition to zero-temperature, inducing a quantum critical end-point.

Uniaxial strain control of bulk ferromagnetism in rare-earth titanates

“…Yet more work is needed to clarify this fundamental issue, in particular uniaxial stress experiments on nominally stoichiometric materials that are closer to the phase boundaries than YTiO 3 . In this regard, it has been recently proposed that uniaxial strain in isovalent chemically-substituted RE titanates could be used to induce a quantum critical end-point [31].…”