Spin Freezing in the Spin Liquid Compound FeAl2O4

TL;DR

This study investigates the magnetic behavior of FeAl₂O₄, revealing a dominant spin liquid phase with embedded glassy regions, distinguished from typical spin glasses by its unique remnant magnetization and susceptibility characteristics.

Contribution

It provides new insights into the coexistence of spin liquid and glassy behaviors in FeAl₂O₄ using advanced magnetic measurement techniques.

Findings

Identified a spin-freezing temperature of ~11.4 K.

Observed broad spin relaxation times indicating complex dynamics.

Revealed a majority spin liquid phase with embedded glassy regions.

Abstract

Spin freezing in the $A$-site spinel FeAl$_2$O$_4$ which is a spin liquid candidate is studied using remnant magnetization and nonlinear magnetic susceptibility and isofield cooling and heating protocols. The remnant magnetization behavior of FeAl$_2$O$_4$ differs significantly from that of a canonical spin glass which is also supported by analysis of the nonlinear magnetic susceptibility term $\chi_3 (T)$. Through the power-law analysis of $\chi_3 (T)$, a spin-freezing temperature, $T_g$ = 11.4$\pm$0.9~K and critical exponent, $\gamma$ = 1.48$\pm$0.59 are obtained. Cole-Cole analysis of magnetic susceptibility shows the presence of broad spin relaxation times in FeAl$_2$O$_4$, however, the irreversible dc susceptibility plot discourages an interpretation based on conventional spin glass features. The magnetization measured using the cooling-and-heating-in-unequal-fields protocol brings more insight to the magnetic nature of this frustrated magnet and reveals unconventional glassy behaviour. Combining our results, we arrive at the conclusion that the present sample of FeAl$_2$O$_4$ consists of a majority spin liquid phase with "glassy" regions embedded.