:Lanthanum manganite
{{short description|Perovskite compound}}
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| ImageFile = LaMnO3 unit cell.png
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| Section1 = {{Chembox Identifiers
| CASNo = 12031-12-8
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| SMILES = [La+3].[Mn+3].[O-2].[O-2].[O-2]
| StdInChI=1S/La.Mn.3O/q2*+3;3*-2
| StdInChIKey = JBZIKYYYMXDQRI-UHFFFAOYSA-N
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| Section2 = {{Chembox Properties
| Formula = LaMnO3
| MolarMass = 241.84 g/mol
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Lanthanum manganite is an inorganic compound with the formula LaMnO3, often abbreviated as LMO. Lanthanum manganite is formed in the perovskite structure, consisting of oxygen octahedra with a central Mn atom. The cubic perovskite structure is distorted into an orthorhombic structure by a strong Jahn–Teller distortion of the oxygen octahedra.
{{cite journal |author=S. Satpathy|year=1996 |journal=Physical Review Letters |title=Electronic Structure of the Perovskite Oxides: La1−xCaxMnO3 |volume=76 |issue=6 |pages=960–963 |doi=10.1103/PhysRevLett.76.960 |pmid=10061595 |bibcode=1996PhRvL..76..960S |display-authors=etal|hdl=10355/9487 |url=http://vinar.vin.bg.ac.rs//bitstream/id/12220/1956.pdf |hdl-access=free }}
LaMnO3 often has lanthanum vacancies as evidenced by neutron scattering. For this reason, this material is usually referred as LaMnO3+ẟ. These vacancies generate a structure with a rhombohedral unit cell in this perovskite. A temperatures below 140 K, this LaMnO3+ẟ semiconductor exhibit a ferromagnetic order.
{{cite journal |author=J. Ortiz, L. Gracia, F. Cancino, U. Pal|year=2020 |journal=Materials Chemistry and Physics |title=Particle dispersion and lattice distortion induced magnetic behavior of La1−xSrxMnO3 perovskite nanoparticles grown by salt-assisted solid-state synthesis |volume=246 |pages=122834 |doi=10.1016/j.matchemphys.2020.122834 |s2cid=213205110 |display-authors=etal}}
Synthesis
Lanthanum manganite can be prepared via solid-state reactions at high temperatures, using their oxides or carbonates.{{cite journal|last1=Bockris|first1=John O'M.|last2=Otagawa|first2=Takaaki|author1-link=John Bockris|title=Mechanism of oxygen evolution on perovskites|journal=The Journal of Physical Chemistry|volume=87|issue=15|year=1983|pages=2960–2971|issn=0022-3654|doi=10.1021/j100238a048}} An alternative method is to use lanthanum nitrate and manganese nitrate as raw materials. The reaction occurs at high temperature after the solvents are vaporized.{{cite journal|last1=Liu|first1=Yuxi|last2=Dai|first2=Hongxing|last3=Du|first3=Yucheng|last4=Deng|first4=Jiguang|last5=Zhang|first5=Lei|last6=Zhao|first6=Zhenxuan|last7=Au|first7=Chak Tong|title=Controlled preparation and high catalytic performance of three-dimensionally ordered macroporous LaMnO3 with nanovoid skeletons for the combustion of toluene|journal=Journal of Catalysis|volume=287|year=2012|pages=149–160|issn=0021-9517|doi=10.1016/j.jcat.2011.12.015}}
Lanthanum manganite alloys
Lanthanum manganite is an electrical insulator and an A-type antiferromagnet. It is the parent compound of several important alloys, often termed rare-earth manganites or colossal magnetoresistance oxides. These families include lanthanum strontium manganite, lanthanum calcium manganite and others.
In lanthanum manganite, both the La and the Mn are in the +3 oxidation state. Substitution of some of the La atoms by divalent atoms such as Sr or Ca induces a similar amount of tetravalent Mn4+ ions. Such substitution, or doping can induce various electronic effects, which form the basis of a rich and complex electron correlation phenomena that yield diverse electronic phase diagrams in these alloys.
{{cite book
|last=Dagotto |first=E. |title=Nanoscale Phase Separation and Colossal Magnetoresistance |date=14 March 2013 |publisher=Springer
|url=https://www.springer.com/materials/book/978-3-540-43245-6
|isbn=978-3-662-05244-0 }}
See also
References
{{reflist}}
{{lanthanum compounds}}
{{manganese compounds}}