Spin-glass dynamics in the presence of a magnetic field: exploration of microscopic properties

Abstract

<p>The synergy between experiment, theory, and simulations enables a microscopic analysis of spin-glass dynamics in a magnetic field in the vicinity of and below the spin-glass transition temperature <em>T</em>g. The spin-glass correlation length, <em>ξ</em>(<em>t</em>, <em>t</em>w; <em>T</em>), is analysed both in experiments and in simulations in terms of the waiting time <em>t</em>w after the spin glass has been cooled down to a stabilised measuring temperature <em>T</em> < <em>T</em>g and of the time <em>t</em> after the magnetic field is changed. This correlation length is extracted experimentally for a CuMn 6 at. % single crystal, as well as for simulations on the Janus II special-purpose supercomputer, the latter with time and length scales comparable to experiment. The non-linear magnetic susceptibility is reported from experiment and simulations, using <em>ξ</em>(<em>t</em>, <em>t</em>w; <em>T</em>) as the scaling variable. Previous experiments are reanalysed, and disagreements about the nature of the Zeeman energy are resolved. The growth of the spin-glass magnetisation in zero-field magnetisation experiments, <em>M</em>ZFC(<em>t</em>, <em>t</em>w; <em>T</em>), is measured from simulations, verifying the scaling relationships in the dynamical or non-equilibrium regime. Our preliminary search for the de Almeida–Thouless line in <em>D</em> = 3 is discussed.</p>