The relative influences of disorder and of frustration on the glassy dynamics in magnetic systems

TL;DR

This study compares the glassy magnetic dynamics of geometrically frustrated systems with spin glasses, revealing that despite minimal disorder, they exhibit similar aging, rejuvenation, and memory effects characteristic of spin glass behavior.

Contribution

It demonstrates that geometrically frustrated magnetic systems show spin glass-like dynamics with minimal disorder, highlighting the influence of frustration on glassy behavior.

Findings

All studied systems exhibit spin glass features below freezing temperature.

Rejuvenation and memory effects are observed, indicating spin glass dynamics.

Differences in temperature response highlight the role of frustration in magnetic relaxation.

Abstract

The magnetisation relaxations of three different types of geometrically frustrated magnetic systems have been studied with the same experimental procedures as previously used in spin glasses. The materials investigated are Y$_2$Mo$_2$O$_7$ (pyrochlore system), SrCr$_{8.6}$Ga$_{3.4}$O$_{19}$ (piled pairs of Kagom\'e layers) and (H$_3$O)Fe$_3$(SO$_4$)$_2$(OH)$_6$ (jarosite compound). Despite a very small amount of disorder, all the samples exhibit many characteristic features of spin glass dynamics below a freezing temperature $T_g$, much smaller than their Curie-Weiss temperature $\theta$. The ageing properties of their thermoremanent magnetization can be well accounted for by the same scaling law as in spin glasses, and the values of the scaling exponents are very close. The effects of temperature variations during ageing have been specifically investigated. In the pyrochlore and the bi-Kagom\'e compounds, a decrease of temperature after some waiting period at a certain temperature $T_p$ re-initializes ageing and the evolution at the new temperature is the same as if the system were just quenched from above $T_g$. However, as the temperature is raised back to $T_p$, the sample recovers the state it had previously reached at that temperature. These features are known in spin glasses as rejuvenation and memory effects. They are clear signatures of the spin glass dynamics. In the Kagom\'e compound, there is also some rejuvenation and memory, but much larger temperature changes are needed to observe the effects. In that sense, the behaviour of this compound is quantitatively different from that of spin glasses.