Magnetic and structure transition of Mn3-xFexO4 solid solutions under high-pressure and high-temperature conditions

IF 1.2 4区地球科学 Q4 MATERIALS SCIENCE, MULTIDISCIPLINARY

Physics and Chemistry of Minerals Pub Date : 2022-10-11 DOI:10.1007/s00269-022-01215-4

Takamitsu Yamanaka, Naohisa Hirao, Yuki Nakamoto, Takashi Mikouchi, Takanori Hattori, Kazuki Komatsu, Ho-kwang Mao

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Abstract

Magnetic and structure transitions of Mn_3–xFe_xO₄ solid solutions under extreme conditions are clarified by neutron time-of-flight scattering diffraction and X-ray Mössbauer measurement. The ferrimagnetic-to-paramagnetic transition temperature (100 °C) of Mn₂FeO₄ spinel is different from the tetragonal-to-cubic structure transition temperature (180 °C). The structure transition temperature decreases with increasing pressure. The transition is not coupled with the magnetic transition. Synchrotron X-ray Mössbauer experiments have revealed the pressure effects on the distribution of Fe²⁺ and Fe³⁺ at the tetrahedral and octahedral sites in the spinel structure. Ferrimagnetic MnFe₂O₄ and Mn₂FeO₄ spinels show sextet spectral features with hyperfine structure elicited by internal magnetic fields. Cubic MnFe₂O₄ spinel and tetragonal Mn₂FeO₄ transform to high-pressure orthorhombic postspinel phase above pressures of 18.4 GPa and 14.0 GPa, respectively. The transition pressure decreases with increasing Mn content. The postspinel phase has a paramagnetic property. Mn₂O₁₀ dimers of two octahedra are linked via common edge in three dimentional direction. The occupancy of Fe²⁺ in the tatrahedral site is decreased with increasig pressure, indicating more oredered structure. Consequently, the inverse parameter of the spinel structure is increased with increasing pressure. The magnetic structure refinements clarify the paramagnetic and ferrimagnetic structure of MnFe₂O₄ and Mn₂FeO₄ spinel as a function of pressure. The magnetic moment is ordered between A and B sites with the anti-parallel distribution along the b axis. The nuclear tetragonal structure (a_N, a_N, c_N) has the ferrimagnetic structure but the orthorhombic magnetic structure has the ferrimagnetic structure with the lattice constants (a_M, b_M, c_M). The magnetic moment is ordered between A and B sites with the anti-parallel distribution along the b_M axis.

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高压和高温条件下Mn3-xFexO4固溶体的磁性和结构转变

通过中子飞行时间散射衍射和x射线Mössbauer测量，阐明了Mn3-xFexO4固溶体在极端条件下的磁性和结构转变。Mn2FeO4尖晶石的铁磁性向顺磁性转变温度(100℃)与四方向立方结构转变温度(180℃)不同。随着压力的增加，结构转变温度降低。跃迁不与磁跃迁耦合。同步加速器x射线Mössbauer实验揭示了压力对尖晶石结构中四面体和八面体位置上Fe2+和Fe3+分布的影响。铁磁性MnFe2O4和Mn2FeO4尖晶石表现出六重光谱特征，具有内部磁场激发的超精细结构。在18.4 GPa和14.0 GPa压力下，立方mn2fe2o4尖晶石和四方Mn2FeO4尖晶石分别转变为高压正交晶相。转变压力随Mn含量的增加而降低。尖晶石后相具有顺磁性。两个八面体的Mn2O10二聚体在三维方向上通过共边连接。随着压力的增加，铁离子在板面体位置的占位率降低，表明结构更加有序。尖晶石结构的逆参数随压力的增大而增大。磁性结构的细化阐明了MnFe2O4和Mn2FeO4尖晶石的顺磁性和铁磁性结构随压力的变化。磁矩在A点和B点之间有序，沿B轴呈反平行分布。核四方结构(aN, aN, cN)具有铁磁结构，而正交磁结构具有具有晶格常数(aM, bM, cM)的铁磁结构。磁矩在A点和B点之间有序，沿bM轴呈反平行分布。

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来源期刊

Physics and Chemistry of Minerals 地学-材料科学：综合

CiteScore

2.90

自引率

14.30%

发文量

审稿时长

3 months

期刊介绍： Physics and Chemistry of Minerals is an international journal devoted to publishing articles and short communications of physical or chemical studies on minerals or solids related to minerals. The aim of the journal is to support competent interdisciplinary work in mineralogy and physics or chemistry. Particular emphasis is placed on applications of modern techniques or new theories and models to interpret atomic structures and physical or chemical properties of minerals. Some subjects of interest are: -Relationships between atomic structure and crystalline state (structures of various states, crystal energies, crystal growth, thermodynamic studies, phase transformations, solid solution, exsolution phenomena, etc.) -General solid state spectroscopy (ultraviolet, visible, infrared, Raman, ESCA, luminescence, X-ray, electron paramagnetic resonance, nuclear magnetic resonance, gamma ray resonance, etc.) -Experimental and theoretical analysis of chemical bonding in minerals (application of crystal field, molecular orbital, band theories, etc.) -Physical properties (magnetic, mechanical, electric, optical, thermodynamic, etc.) -Relations between thermal expansion, compressibility, elastic constants, and fundamental properties of atomic structure, particularly as applied to geophysical problems -Electron microscopy in support of physical and chemical studies -Computational methods in the study of the structure and properties of minerals -Mineral surfaces (experimental methods, structure and properties)