Changeover from Glassy ferromagnetism of the orbital domain state to long range ferromagnetic ordering in La{_{0.9}}Sr_{0.1}MnO{_3}

TL;DR

This study investigates the low-temperature magnetic phases of La${_{0.9}}$Sr${_{0.1}}$MnO${_3}$, revealing a transition from orbital domain glassy states to long-range ferromagnetic order upon self-doping, with detailed analysis of inhomogeneity and metastability.

Contribution

It demonstrates the disappearance of glassy orbital domain states in non-stoichiometric La${_{0.9}}$Sr${_{0.1}}$MnO${_3.08}$, clarifying the nature of magnetic inhomogeneity and phase transition mechanisms.

Findings

Glassy behavior linked to orbital domain states at low temperature.

Inhomogeneity reduces and glassy features vanish in non-stoichiometric samples.

Magnetic response explained by domain wall dynamics in homogeneous ferromagnet.

Abstract

An attempt is made to resolve the controversy related to the low temperature phase (ground state) of the low-doped ferromagnetic (FM)- insulator(I) manganite through bulk magnetic measurements on La${_{0.9}}$Sr$_{0.1}$MnO${_3}$ sample. It is shown that the FM phase, formed out of well defined transition in the low-doped system, becomes inhomogeneous with decrease in temperature. This inhomogeniety is considered to be an outcome of the formation of orbital domain state of e$_g$-electrons having hole rich (metallic) walls separating the hole deficient (insulating) regions. The resulting complexity brings in metastability and glassy behaviour within the FM phase at low temperature, however, with no resemblance to spin glass, cluster glass or reentrant phases. It shows ageing effect without memory but magnetic relaxation shows signatures of inter-cluster interaction. The energy landscape picture of this glassy phase is described in terms of hierarchical model. Further, it is shown that this inhomogeneity disappear in La${_{0.9}}$Sr$_{0.1}$MnO$_{3.08}$ where, the orbital domain state is destroyed by self doping resulting in reduction of Mn$^{3+}$ and hence e$_g$-electrons. The ferromagnetic phase of the non-stoichiometric sample, does not show glassy behaviour. It neither follows 'hierarchical model' nor 'droplet model' generally used to explain glassy or inhomogeneous systems. Its magnetic response can be explained simply from the domain wall dynamics of otherwise homogeneous ferromagnet.