Spin freezing in the A-site spinel FeAl2​O4​ 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 FeAl2​O4​ differs significantly from that of a
canonical spin glass which is also supported by analysis of the nonlinear
magnetic susceptibility term χ3​(T). Through the power-law analysis of
χ3​(T), a spin-freezing temperature, Tg​ = 11.4±0.9~K and critical
exponent, γ = 1.48±0.59 are obtained. Cole-Cole analysis of magnetic
susceptibility shows the presence of broad spin relaxation times in
FeAl2​O4​, 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 FeAl2​O4​ consists of a majority spin
liquid phase with "glassy" regions embedded.Comment: 5 pages, 6 figs, 2-column, Accepted to Phys. Rev.