{"title":"Antiferromagnetic to ferromagnetic phase transition as a transition to partial ordered spins. Application to La1−xCaxMnO3 in the doping range x ≥ 0.50","authors":"","doi":"10.1016/j.physleta.2024.129904","DOIUrl":null,"url":null,"abstract":"<div><p>Magnetic state is a partial ordered state if only part of the electrons in the system give contribution to the magnetic order. We study Heisenberg model of two sublattice spin system, on the body-centered cubic lattice, with antiferromagnetic nearest neighbors exchange of sublattice A and B spins and two different ferromagnetic exchange constants for sublattice A (<span><math><msup><mrow><mi>J</mi></mrow><mrow><mi>A</mi></mrow></msup></math></span>) and B (<span><math><msup><mrow><mi>J</mi></mrow><mrow><mi>B</mi></mrow></msup></math></span>) spins. When <span><math><msup><mrow><mi>J</mi></mrow><mrow><mi>A</mi></mrow></msup><mo>></mo><msup><mrow><mi>J</mi></mrow><mrow><mi>B</mi></mrow></msup></math></span> the system undergoes transition from paramagnetism to ferromagnetism at Curie temperature <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>C</mi></mrow></msub></math></span>. Only the sublattice A spins give contribution to the magnetization of the system. Upon cooling, the system possesses ferromagnetism to antiferromagnetism transition at Néel temperature <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>N</mi></mrow></msub><mo><</mo><msub><mrow><mi>T</mi></mrow><mrow><mi>C</mi></mrow></msub></math></span>. Below <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>N</mi></mrow></msub></math></span> sublattice A and B electrons give contribution to the magnetization. The transition is a partial ordered transition. There is thermodynamic evidence for this transition in the magnetic specific heat of the system. As a function of temperature there are two maxima. At high temperature <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>C</mi></mrow></msub></math></span> it is <em>λ</em>-type. At lower temperature <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>N</mi></mrow></msub></math></span> it characterizes the transition from ferromagnetism to antiferromagnetism. As an example of ferromagnetism to antiferromagnetism partial ordered transition we consider the material <span><math><mi>L</mi><msub><mrow><mi>a</mi></mrow><mrow><mn>1</mn><mo>−</mo><mi>x</mi></mrow></msub><mi>C</mi><msub><mrow><mi>a</mi></mrow><mrow><mi>x</mi></mrow></msub><mi>M</mi><mi>n</mi><msub><mrow><mi>O</mi></mrow><mrow><mn>3</mn></mrow></msub></math></span> in the doping range <span><math><mi>x</mi><mo>≥</mo><mn>0.50</mn></math></span>. Our calculations reproduce the experimental magnetization-temperature curve.</p></div>","PeriodicalId":20172,"journal":{"name":"Physics Letters A","volume":null,"pages":null},"PeriodicalIF":2.3000,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Physics Letters A","FirstCategoryId":"101","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S037596012400598X","RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"PHYSICS, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Magnetic state is a partial ordered state if only part of the electrons in the system give contribution to the magnetic order. We study Heisenberg model of two sublattice spin system, on the body-centered cubic lattice, with antiferromagnetic nearest neighbors exchange of sublattice A and B spins and two different ferromagnetic exchange constants for sublattice A () and B () spins. When the system undergoes transition from paramagnetism to ferromagnetism at Curie temperature . Only the sublattice A spins give contribution to the magnetization of the system. Upon cooling, the system possesses ferromagnetism to antiferromagnetism transition at Néel temperature . Below sublattice A and B electrons give contribution to the magnetization. The transition is a partial ordered transition. There is thermodynamic evidence for this transition in the magnetic specific heat of the system. As a function of temperature there are two maxima. At high temperature it is λ-type. At lower temperature it characterizes the transition from ferromagnetism to antiferromagnetism. As an example of ferromagnetism to antiferromagnetism partial ordered transition we consider the material in the doping range . Our calculations reproduce the experimental magnetization-temperature curve.
期刊介绍:
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