Estimation of characteristic size of ferromagnetic clusters forming above T$_C$ in Nd$_{0.75}$Ba$_{0.25}$MnO$_3$ manganite

TL;DR

This study investigates ferromagnetic cluster formation above the Curie temperature in Nd-Ba-Mn-O manganites using neutron depolarization and second harmonic magnetization measurements, estimating cluster size and concentration.

Contribution

It provides the first estimation of ferromagnetic cluster size and concentration above T_C in Nd-Ba-Mn-O manganites by combining neutron depolarization and magnetization data.

Findings

Ferromagnetic clusters form below T* > T_C.

Cluster size and concentration increase with doping.

Depolarization and M2 data agree on cluster growth.

Abstract

We present the data on depolarization of polarized neutron beam and second harmonic of magnetization ($M_2$) for Nd$_{1-x}$Ba$_x$MnO$_3$ ($x$ = 0.23, the Curie temperature $T_C \approx$ 124 K; $x$ = 0.25, $T_C \approx$ 129 K) manganites. The depolarization starts to develop below $T$* $\approx$ 147 K $> T_C$ for both samples, being larger in x = 0.25 compound. This evidences the arising of a ferromagnetic (F) cluster phase below $T$* and a growth of its relative volume fraction with increasing doping concentration that agrees with the previously published results of $M_2$ study. A characteristic size of the F clusters and their concentration are estimated combining the neutron depolarization and $M_2$ data for $x$ = 0.25 manganite.