Griffiths-like phase and magnetic correlations at high fields in Gd5Ge4

Abstract

Magnetic correlations appearing in polycrystalline Gd${}_{5}$Ge${}_{4}$ are studied. On the one hand, ac susceptibility measurements as functions of temperature at several dc fields and frequencies show the existence of ferromagnetic (FM) and antiferromagnetic (AFM) correlations in the paramagnetic (PM) region, where a Griffiths-like phase appears below $~$225 K. The value for the effective magnetic moment within the Griffiths-like phase is 10.1 ${\ensuremath{\mu}}_{B}$. FM correlations also extended all the way into the AFM phase below $~$127 K. The onset of the Griffiths-like phase is associated with an effective critical slowing down. On the other hand, high field magnetization measurements reveal the presence of FM and AFM correlations in the three magnetic phases (PM, FM, and AFM), giving rise to a variety of mixed magnetic states. In particular, at high fields the magnetostructural transition takes place in several stages that extend along a wide temperature range. A three-dimensional $(T,H,M)$ phase diagram is proposed, including the new experimental findings.