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arXiv · 2203.03676

Microscopic insights of magnetism in Sm$ _{2} $NiMnO$ _{6} $ double perovskite

Supriyo Majumder·Malvika Tripathi·H. E. Fischer·D. O. de Souza·L. Olivi·A. K. Sinha·R. J. Choudhary·D. M. Phase
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Abstract

The functional characteristics of double perovskites with unique ferromagnetic-insulator ground state have been controversial due to the unavoidable presence of anti-site disorders (ASDs). Here, we aim to investigate the origin of magnetic ordering on local and global scales in Sm$_{2}$NiMnO$_{6}$ (SNMO) double perovskite system. Different calcination routes are exploited to generate different cation arrangements in SNMO and the corresponding magnetic configurations are examined using the high energy (E $ \sim $0.3 eV) `hot neutrons', which has helped to overcome Sm absorption as well as to record total (Bragg's+diffuse) scattering profiles with high momentum transfer (Q$ _{max} \sim $24 angstrom$ ^{-1} $). We have observed that the Ni-Mn sublattice adopts long range collinear ferromagnetic $ F_{x}F_{z} $ structure with commensurate $k$=(0, 0, 0) propagation vector, below ordering temperature T $ \lesssim $ 160 K, irrespective of variable ASD concentrations. In addition, the signatures indicating the antiparallel polarization of Sm paramagnetic moments with respect to Ni-Mn network, are noticed in the vicinity of anomalous magnetic transitions at T $ \lesssim $ 35 K. The real space pair distribution function calculations have provided a direct visualization of ASDs by means of broadening in Ni/Mn-Mn/Ni linkage. Employing the Reverse Monte Carlo approach on diffuse magnetic scattering profiles, we have observed the negative spin-spin correlation function which suggests the Ni-Ni antiferromagnetic exchange interactions ranging up to first nearest neighbor distance. These results confirm that the existence of ASDs in cation ordered host matrix leads to competing ferromagnetic-antiferromagnetic phases in a broad temperature range, which quantitatively governs the temperature dependent bulk magnetic observables of SNMO system.

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Supriyo Majumder, Malvika Tripathi, H. E. Fischer, D. O. de Souza, L. Olivi, A. K. Sinha, R. J. Choudhary, D. M. Phase. 2022-03-07. Microscopic insights of magnetism in Sm$ _{2} $NiMnO$ _{6} $ double perovskite. https://doi.org/10.1103/physrevb.105.094425

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