muSR Investigation of magnetically ordered states in A-site ordered perovskite manganites RBaMn2O6 (R = Y and La)

TL;DR

This study uses muon spin relaxation to compare the magnetic ordering in two A-site ordered perovskite manganites, revealing inhomogeneous ferromagnetic behavior in LaBaMn2O6 and homogeneous antiferromagnetic order in YBaMn2O6.

Contribution

It provides the first muSR comparison of magnetic states in these two specific A-site ordered manganites, highlighting their distinct magnetic inhomogeneity and homogeneity.

Findings

LaBaMn2O6 exhibits inhomogeneous ferromagnetic phase below 330 K.

YBaMn2O6 shows homogeneous magnetic states in both charge/orbital ordered and paramagnetic phases.

Antiferromagnetic order in YBaMn2O6 is well-defined and homogeneous.

Abstract

The magnetically ordered states of the A-site ordered perovskite manganites LaBaMn2O6 and YBaMn2O6 have been investigated by muon spin relaxation in zero external magnetic field. Our data reveal striking differences in the nature of the magnetically ordered state of these materials. For LaBaMn2O6, the muSR time-spectra in the ferromagnetic state below ~ 330 K reveal a strongly inhomogeneous phase, reminiscent of a Griffiths phase. Within this magnetically inhomogeneous phase, an antiferromagnetic state develops below 150 K, which displays well defined static internal magnetic fields, but reaches only 30% of the volume fraction at low temperatures. A broad distribution of muSR relaxation rates is inferred down to the lowest temperatures. This behavior is similar to the A-site disordered La0.5Ba0.5MnO3. On the other hand, for YBaMn2O6, the muSR time spectra for both (i) the charge and orbital ordered and (ii) the paramagnetic phases reveal rather homogeneous states, namely, an exponential relaxation in the paramagnetic state and well defined muon spin oscillation in the antiferromagnetic state.