Atomic-scale chemical fluctuation inLaSrVMoO6, a proposed half-metallic antiferromagnet

Abstract

Half-metallic antiferromagnets ͑HMAFMs͒ have been proposed theoretically long ago but have not been realized experimentally yet. Recently, a double perovskite compound, LaSrVMoO 6 , has been claimed to be an almost real HMAFM system. Here, we report detailed experimental and theoretical studies on this compound. Our results reveal that the compound is neither a half-metal nor an ordered antiferromagnet. Most importantly, an unusual chemical fluctuation is observed locally, which finally accounts for all the electronic and magnetic properties of this compound.

Evaluation of half-metallic antiferromagnetism inA2CrFeO6(A<

“…The reasons for this are not yet clear, but some seem to result from antisite disorder on B and B ′ sites. 15 In particular, in systems having 3d ions in both B and B ′ sites, similar ionic radii often prevent a well-ordered sample from being established, resulting in undermined compensation of magnetic moments. …”

Epitaxial thin films of ordered double perovskite SrLaVMoO6

“…SrLaVMoO 6 with an ordered double perovskite has been 1237 suggested to be a HMAF state by considering antiparallel alignment of alternately occupied V 3+ (3d 2 ) and Mo 4+ (4d 2 ) spins at the B-site of the perovskite structure. However, a recent report on experimental studies of bulk polycrystalline SrLaVMoO 6 along with electronic-structure calculations [15] have suggested that an atomic-scale chemical fluctuation played an important role and should be incorporated in order to account for the electronic and magnetic properties of the compound. The authors proposed a picture of very local antiferromagnetic insulating LaVO 3 -and paramagnetic metallic SrMoO 3 -like regions to explain their x-ray absorption fine structure results on SrLaVMoO 6 with a completely disordered double perovskite structure.…”

LaSrVMoO6: A case study forA-site covalency-driven local cationic order in double perovskites

“…A couple of reports claimed this system to be the first experimentally realized HMAFM, 6,7 while ab-initio band structure calculation results based on the experimental crystal structure opined otherwise, 8,9 confirming half-metallicity but predicting robust ferrimagnetic ground state for this compound. Therefore, quite contradictory depictions existed till our experiments 5 revealed the fact that the ground state of this compound is neither halfmetallic nor antiferromagnetic. Most importantly, our study showed that the local chemical , that might be present in a multi-cation system, needs to be considered while probing the structure and properties of the material.…”

“…But, the present study established that the most 'homogeneous' sample is indeed the one that we have already reported earlier. 5 Further, our theoretical calculation showed why this structure with chemical fluctuation has to be the most stable configuration for LaSrVMoO 6 ; where the driving force is the preference of La ions to form strong covalent linkages with the O ions that are linked to V ions, over the ones connected to Mo. The distinction arises due to the more ionic nature of V ions compared to Mo ions, finally resulting in La,V-rich, and the consequent Sr,Mo-rich regions.…”

“…4 However, unlike all previous descriptions, LaSrVMoO 6 (LSVMO) presented a completely distinct cationic arrangement, as was revealed during the investigation of its debatable half-metallic antiferromagnetic (HMAFM) state. 5 Initially, this compound was suggested to be a half-metallic antiferromagnet by considering antiparallel alignment of alternately occupied V 3+ (3d 2 ) and Mo 4+ (4d 2 ) spins in a rock-salt type double perovskite structure. A couple of reports claimed this system to be the first experimentally realized HMAFM, 6,7 while ab-initio band structure calculation results based on the experimental crystal structure opined otherwise, 8,9 confirming half-metallicity but predicting robust ferrimagnetic ground state for this compound.…”