Ferromagnetic cluster-glass state in itinerant electron system Sr1-xLaxRuO3

TL;DR

This study reveals a cluster-glass magnetic state in Sr1-xLaxRuO3, where ferromagnetic order is suppressed and replaced by inhomogeneous spin clusters, with properties linked to itinerant Ru 4d electrons.

Contribution

It demonstrates the coexistence of cluster-glass behavior and itinerant electron magnetism in Sr1-xLaxRuO3, highlighting the role of Ru 4d electrons in this complex magnetic state.

Findings

Ferromagnetic order is suppressed with La doping.

Frequency-dependent peak T* indicates cluster-glass behavior.

Large specific heat coefficient gamma suggests itinerant Ru 4d electrons.

Abstract

The magnetic and electronic properties of Sr1-xLaxRuO3 were studied by means of dc-magnetization, ac-susceptibility, specific heat, and electrical resistivity measurements. The dc-magnetization and ac-susceptibility measurements have revealed that the transition temperature and the ordered moment of the ferromagnetic order are strongly suppressed as La is substituted for Sr. The ac-susceptibility exhibits a peak at T* due to the occurrence of spontaneous spin polarization. Furthermore, we observed that T* shows clear frequency variations for x>= 0.3. The magnitude of the frequency shifts of T* is comparable to that of cluster-glass systems, and the frequency dependence is well described in terms of the Vogel-Fulcher law. On the other hand, it is found that the linear specific heat coefficient gamma enhances with the suppression of the ferromagnetic order. The relatively large gamma values reflect the presence of the Ru 4d state at Fermi level, and hence, the magnetism of this system is considered to be tightly coupled with the itinerant characteristics of the Ru 4d electrons. The present experimental results and analyses suggest that the intrinsic coexistence of the spatially inhomogeneous magnetic state and the itinerant nature of the Ru 4d electrons is realized in this system, and such a feature may be commonly involved in La- and Ca-doped SrRuO3.