{"id":31530,"date":"2025-11-12T10:09:20","date_gmt":"2025-11-12T04:24:20","guid":{"rendered":"https:\/\/www.revoscience.com\/en\/?p=31530"},"modified":"2025-11-12T10:17:56","modified_gmt":"2025-11-12T04:32:56","slug":"scientists-capture-a-new-polar-orders-true-ferrielectric-material-discovered","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/scientists-capture-a-new-polar-orders-true-ferrielectric-material-discovered\/","title":{"rendered":"Scientists capture a new polar orders: true ferrielectric material discovered"},"content":{"rendered":"\n
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AI-generate Image:<\/sup><\/em><\/figcaption><\/figure>\n\n\n

SCIENCE CHINA PRESS<\/p><\/div><\/div>\n\n\n

For decades, condensed-matter physics has pursued a long-hypothesized polar state known as ferrielectricity\u2014predicted to bridge the properties of ferroelectrics (FE) and antiferroelectrics (AFE), yet remaining experimentally elusive in any single-phase crystal.<\/p>\n\n\n\n

A collaboration led by Professor Junling Wang of City University of Hong Kong and Professor Shuai Dong of Southeast University\u00a0has now brought this picture into clear view. Writing in National Science Review, the team reports the first unambiguous evidence of irreducible ferrielectricity in a hybrid crystal, (MV)[SbBr5<\/sub>] (MV2+<\/sup>\u00a0<\/sub>= methylviologen), establishing ferrielectricity as a functionally distinct polar order rather than a mere re-labeling of ferroelectricity.<\/p>\n\n\n\n

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Polarization in (MV)[SbBr5<\/sub>] arises from two contributions: Br displacements within the inorganic [SbBr5<\/sub>]2-\u00a0framework and the concerted displacement of the organic MV cations. These form non-collinear, nearly antiparallel dipolar sublattices of unequal magnitude and produce a stepwise field-driven switching: at low fields, the net polarization reverses without flipping individual dipoles; at intermediate fields, the organic sublattice undergoes an AFE\u2192FE transition; at higher fields, the inorganic sublattice follows\u2014yielding multi-peak I\u2013E\/C\u2013E signatures. The electric-field-induced polar-to-polar transition (FiE\u2192FE) enables field tuning of spin\u2013orbit coupling (SOC), manifested as a voltage-controllable circular photogalvanic effect (CPGE). CREDIT: SCP <\/sup><\/em><\/figcaption><\/figure>\n\n\n\n

What makes ferrielectricity special?<\/strong><\/p>\n\n\n\n

Ferrielectricity was originally formulated by analogy to ferrimagnetism: microscopically, multiple dipoles coexist within a unit cell\u2014either antiparallel but unequal in magnitude, or oriented at a finite angle\u2014thereby producing a net polarization; macroscopically, the net polarization must be switchable by an electric field. However, unlike magnetic moments, the selection of an electric dipole is relative and non-unique, so particular structural analyses may obscure the underlying physics\u2014many so-called ferrielectrics can be reduced to ordinary ferroelectrics by merging multiple dipoles into a single one.<\/p>\n\n\n\n

Hence the central question: if a material switches exactly like a ferroelectric, should it be classified as a new ferroic order merely because its microscopic description is complex? More fundamentally: does a truly \u201cirreducible ferrielectric\u201d exist whose switching behavior is intrinsically different from ferroelectrics\u2014that is, a ferrielectric worthy of separate classification by virtue of distinctive functional functionality?<\/p>\n\n\n\n

(MV)[SbBr\u2085]: multi-dipole system<\/strong><\/p>\n\n\n\n

The team designed (MV)[SbBr5<\/sub>] as an ideal platform to host this state. Its polarization arises from two sources: Br displacements within the [SbBr5<\/sub>]2-<\/sup> framework and the concerted motion of the MV cation. These organic\u2013inorganic contributions form non-collinear, anti-parallel dipolar sublattices of unequal magnitude, producing a small net polarization, as confirmed by structural analysis and second-harmonic generation (SHG).<\/p>\n\n\n\n

Three hallmarks set this <\/strong>ferrielectric <\/strong>state apart.<\/strong><\/p>\n\n\n\n

First, (MV)[SbBr5<\/sub>] shows a switchable net polarization<\/strong>, satisfying the macroscopic switchability criterion highlighted in earlier definitions.<\/p>\n\n\n\n

Second, it displays asynchronous switching<\/strong>: temperature- and frequency-dependent electrical measurements reveal multiple current peaks during polarization reversal, a fingerprint that the organic and inorganic sublattices respond on different timescales. Microscopically, the MV2+<\/sup> sublattice switches via lower-energy reorientations\/translations, while the [SbBr5<\/sub>]2-<\/sup> framework requires higher-barrier lattice displacements\u2014naturally producing distinct relaxation times and activation energies.<\/p>\n\n\n\n

Third, the crystal undergoes a field-driven polar-to-polar transition<\/strong> (FiE\u2192FE).<\/p>\n\n\n\n

Together, these observations map a stepwise pathway\u2014FiE(\u2212)<\/sup> \u2192 FiE(+)<\/sup> \u2192 FE1 \u2192 FE2\u2014that cannot be compressed into a single ferroelectric or antiferroelectric order parameter. At low fields, the net polarization can be reversed without switching individual dipoles; at intermediate fields the organic sublattice first undergoes an AFE\u2192FE transition; and at higher fields the inorganic sublattice follows, forming an inherently asynchronous sequence.<\/p>\n\n\n\n

Computation meets experiment.<\/strong><\/p>\n\n\n\n

First-principles calculations reproduce the hierarchy of switching barriers (organic < inorganic), explaining the observed multi-peak I\u2013E\/C\u2013E profiles and the sequential nature of the transitions. The theoretical and experimental narratives align: ferrielectricity here is not a semantic construct\u2014it is a dynamical reality with distinct, testable signatures.<\/p>\n\n\n\n

Function follows order.<\/strong><\/p>\n\n\n\n

Beyond the \u201cwhat,\u201d the study highlights the \u201cso what.\u201d By driving the FiE\u2192FE transition with an electric field, the team reconfigures crystal structure and tunes spin\u2013orbit coupling (SOC). This directly modulates the circular photogalvanic effect (CPGE)\u2014the material\u2019s left-\/right-handed light response\u2014demonstrating voltage control over a SOC. Such coupling among structure, spin, and light in a single-phase material points to electric-field control of spin, circularly polarized photodetectors, and reconfigurable chiral photonics.<\/p>\n\n\n\n

Why it matters.<\/strong><\/p>\n\n\n\n

This work not only resolves a long-standing fundamental question but also establishes a new paradigm: we should define new states of matter by their functional behavior, not just their static structure. It provides a novel approach for the electric field control of spins and light response, with potential applications in spintronics, low-energy multi-state memory, and chiral optoelectronics.<\/p>\n\n\n\n

The hybrid crystal (MV)[SbBr5<\/sub>] thus serves as a foundational material platform, showcasing a new principle for simultaneously controlling charge, spin, and light degrees of freedom via electric fields.<\/p>\n","protected":false},"excerpt":{"rendered":"

For decades, condensed-matter physics has pursued a long-hypothesized polar state known as ferrielectricity\u2014predicted to bridge the properties of ferroelectrics (FE) and antiferroelectrics (AFE), yet remaining experimentally elusive in any single-phase crystal.<\/p>\n","protected":false},"author":2,"featured_media":31538,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-31530","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2025\/11\/feero-electric-material.webp",640,448,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2025\/11\/feero-electric-material-200x200.webp",200,200,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2025\/11\/feero-electric-material.webp",640,448,false],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2025\/11\/feero-electric-material.webp",640,448,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2025\/11\/feero-electric-material.webp",640,448,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2025\/11\/feero-electric-material.webp",640,448,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2025\/11\/feero-electric-material.webp",640,448,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2025\/11\/feero-electric-material.webp",640,448,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2025\/11\/feero-electric-material.webp",640,448,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2025\/11\/feero-electric-material-600x448.webp",600,448,true],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2025\/11\/feero-electric-material-600x448.webp",600,448,true],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2025\/11\/feero-electric-material.webp",640,448,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2025\/11\/feero-electric-material-550x360.webp",550,360,true],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2025\/11\/feero-electric-material-95x65.webp",95,65,true],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2025\/11\/feero-electric-material.webp",640,448,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2025\/11\/feero-electric-material-96x96.webp",96,96,true],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2025\/11\/feero-electric-material-150x105.webp",150,105,true]},"author_info":{"info":["SCIENCE CHINA PRESS"]},"category_info":"Research<\/a>","tag_info":"Research","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/31530","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=31530"}],"version-history":[{"count":2,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/31530\/revisions"}],"predecessor-version":[{"id":31539,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/31530\/revisions\/31539"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/31538"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=31530"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=31530"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=31530"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}