Memory and rejuvenation in a spin glass

TL;DR

This study investigates the temperature-dependent magnetisation behavior of a Cu(Mn) spin glass, revealing complex relaxational and frozen-in components, and the imprinting of unidirectional excess magnetisation during aging and cooling protocols.

Contribution

It provides new insights into the memory and rejuvenation effects in spin glasses through detailed magnetic measurements and thermal protocols.

Findings

Magnetisation comprises relaxational and frozen-in parts.

Memory effects include unidirectional excess magnetisation.

Magnetic response depends on aging and thermal history.

Abstract

The temperature dependence of the magnetisation of a Cu(Mn) spin glass ($T_g$ $\approx$ 57 K) has been investigated using weak probing magnetic fields ($H$ = 0.5 or 0 Oe) and specific thermal protocols. The behaviour of the zero-field cooled, thermoremanent and isothermal remanent magnetisation on (re-)cooling the system from a temperature (40 K) where the system has been aged is investigated. It is observed that the measured magnetisation is formed by two parts: (i) a temperature- and observation time-dependent thermally activated relaxational part governed by the age- and temperature-dependent response function and the (latest) field change made at a lower temperature, superposed on (ii) a weakly temperature-dependent frozen-in part. Interestingly we observe that the spin configuration that is imprinted during an elongated halt in the cooling, if it is accompanied by a field induced magnetisation, also includes a unidirectional excess magnetisation that is recovered on returning to the ageing temperature.