Spin and orbital frustration in MnSc_2S_4 and FeSc_2S_4

TL;DR

This study investigates the magnetic and orbital properties of MnSc_2S_4 and FeSc_2S_4, revealing strong frustration and spin-orbital liquid behavior in FeSc_2S_4 and spin liquid behavior in MnSc_2S_4.

Contribution

It provides experimental evidence of spin and orbital frustration in these compounds, identifying FeSc_2S_4 as a spin-orbital liquid and MnSc_2S_4 as a spin liquid.

Findings

FeSc_2S_4 is a spin-orbital liquid with no order down to 50 mK.

MnSc_2S_4 exhibits spin liquid behavior above 2 K.

Both compounds show strong magnetic frustration.

Abstract

Crystal structure, magnetic susceptibility, and specific heat were measured in the normal cubic spinel compounds MnSc_2S_4 and FeSc_2S_4. Down to the lowest temperatures, both compounds remain cubic and reveal strong magnetic frustration. Specifically the Fe compound is characterized by a Curie-Weiss temperature \Theta_{CW}= -45 K and does not show any indications of order down to 50 mK. In addition, the Jahn-Teller ion Fe^{2+} is orbitally frustrated. Hence, FeSc_2S_4 belongs to the rare class of spin-orbital liquids. MnSc_2S_4 is a spin liquid for temperatures T > T_N \approx 2 K.