Hidden Frustration in Double-Perovskite CaFeTi$_2$O$_6$

TL;DR

This study investigates the magnetic behavior of CaFeTi$_2$O$_6$, revealing hidden frustration likely caused by orbital effects, leading to a potential quantum spin liquid state despite lacking conventional frustration mechanisms.

Contribution

It introduces the concept of orbital modulation as a source of hidden magnetic frustration in CaFeTi$_2$O$_6$, expanding understanding of quantum spin liquids beyond traditional frustration models.

Findings

No long-range magnetic order observed below 5.5 K.

Presence of a spin-glass-like state suppressed by magnetic field.

Evidence of a potential quantum spin liquid with $T^{1.6}$ specific heat dependence.

Abstract

We study the magnetic properties of CaFeTi$_2$O$_6$ (CFTO) by high-field magnetization and specific heat measurements. While the magnetic susceptibility data yield a vanishingly small Curie-Weiss temperature, the magnetic moments are not fully polarized in magnetic field up to 60 T, which reveals a large spin exchange energy scale. Yet, the system shows no long range magnetic order but a spin-glass-like state below 5.5 K in zero field, indicating strong magnetic frustration in this system. Applying magnetic field gradually suppresses the spin-glass-like state and gives rise to a potential quantum spin liquid state whose low-temperature specific heat exhibits a $T^{1.6}$ power-law. Crucially, conventional mechanisms for frustration do not apply to this system as it possesses neither apparent geometrical frustration nor exchange frustration. We suggest that the orbital modulation of exchange interaction is likely the source of hidden frustration in CFTO, and its full characterization may open a new route in the quest for quantum spin liquids.