Preparation,structure And Properties Of New Sb Doped BaMnO₃ Hexagonal Perovskite

Perovskite manganese oxide is a typical multifunctional magnetoelectric material due to its internal coupling between spin,orbit,charge and lattice and other degrees of freedom,showing rich magnetic,electrical and optical properties,and has always been one of the hot spots in scientific research.In this paper,several hexagonal perovskite manganese oxides with spin glass and magnetic resistance were synthesized by medium and high temperature solid-state method and molten salt method,mainly including 12R hexagonal perovskite new compound Ba₄SbMn₃O₁₂,10H hexagonal perovskite Ba₅Sb_0.7Mn_4.3O₁₅,compound Pb₃Mn₃Mg₂V₂O₁₆ with kagomélattice,and four-core manganese cluster compound K₃Li Mn₄（MoO₄）₆ with Y-type geometry.Combined with X-ray diffraction（XRD）,neutron diffraction（ND）,scanning electron microscopy（SEM）and transmission electron microscopy（TEM）,phase analysis and structure elucidation of materials,and the magnetic and electrical properties of these compounds were studied by using MPMS-3 magnetic measurement system,and the relationship between structure and properties was established.The main research results are as follows:（1）A new hexagonal perovskite compound with the chemical formula Ba₄SbMn₃O₁₂ was synthesized.The compound has a 12R structure and a space group of R3m.The crystal structure consists of a Mn₃O₁₂ trimer and an Sb O₆ octahedron formed by three coplanar octahedrons,in which each Sb O₆ octahedron is connected with six linear trimers Mn₃O₁₂ covertices to form a[SbMn₃O₁₂]_∞three-dimensional skeleton structure,the Ba O₃ layer is arranged in the（cchh）₃manner along the c axis,and Sb/Mn co-occupies in the angular shared octahedron.Magnetic studies have shown that the sample exhibits a ferromagnetic spin freezing transition at 11.5 K and a dynamic ferromagnetic cluster below 70 K.Due to the presence of Mn ions in the cluster Mn-Mn distance and M1 site in Ba₄SbMn₃O₁₂,the compound exhibits both cluster magnetism and competitive ferromagnetic and antiferromagnetic interactions,and finally a ferromagnetic spin glass transition occurs at low temperature.The four-electrode method test showed that the compound exhibited semiconductor conductive behavior without obvious magnetoresistance effect.（2）A series of 10H Ba₅Sb_0.7+0.7xMn_4.3O₁₅ solid solutions were synthesized.With the increase of Sb content added to the reaction,the 10H Ba₅Sb_0.7Mn_4.3O₁₅ chalcogenide phase transformed into 12R Ba₅Sb_1.06Mn_3.94O₁₅.This phase transformation phenomenon indicates that the stability of the 12R and 10H structures is closely related to the ordered distribution of Sb/Mn,which in turn is regulated by the Sb₂O₃ added during the synthesis process.The Sb/Mn occupancy ratio was determined by neutron diffraction,and magnetic tests showed that the samples underwent abundant continuous magnetic transitions with decreasing temperature,including possible continuous spin glass transitions near 100 K and 125 K in the high temperature region and spin tilting at 50 K.（3）Single crystal samples of Pb₃Mn₃Mg₂V₂O₁₆ were grown by the molten salt method.The structure of Pb₃Mn₃Mg₂V₂O₁₆ single crystal was determined by single crystal X-ray diffraction,and magnetic tests showed that the antiferromagnetic interactions within the kagomélayers produced a strong resistance to frustration.And the large layer spacing effectively suppressed the magnetic ordering and eventually led to the spin glass transition.A polycrystalline sample of K₃Li Mn₄（MoO₄）₆ was prepared using a medium-temperature solid-state method,and magnetic tests showed that K₃Li Mn₄（MoO₄）₆ underwent spin-tilt antiferromagnetic ordering at 3.7 K and exhibited some spin-deflective effects.