{"id":273133,"date":"2025-11-05T13:59:10","date_gmt":"2025-11-05T13:59:10","guid":{"rendered":"https:\/\/www.newsbeep.com\/us\/273133\/"},"modified":"2025-11-05T13:59:10","modified_gmt":"2025-11-05T13:59:10","slug":"a-new-look-at-magnetic-excitations-physics-world","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/us\/273133\/","title":{"rendered":"a new look at magnetic excitations \u2013 Physics World"},"content":{"rendered":"

New research reveals how quantum effects in double-exchange ferromagnets drive unexpected magnetic behaviour<\/p>\n

\t\t\t\t\t\t\t\t\t\t
\n\t\t\t\t\t\t\t\t\t\t\t\t\"Iron-based
\n\t\t\t\t\t\t\t\t\t\t<\/a><\/p>\n

\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tIron-based material (Courtesy: iStock\/Assistantua)<\/p>\n

For almost a century, physicists have tried to understand why and how materials become magnetic. From refrigerator magnets to magnetic memories, the microscopic origins of magnetism remain a surprisingly subtle puzzle \u2014 especially in materials where electrons behave both like individual particles and like a collective sea.<\/p>\n

In most transition-metal compounds, magnetism comes from the dance between localized and mobile electrons. Some electrons stay near their home atoms and form tiny magnetic moments (spins), while others roam freely through the crystal. The interaction between these two types of electrons produces \u201cdouble-exchange\u201d ferromagnetism \u2014 the mechanism that gives rise to the rich magnetic behaviour of materials such as manganites, famous for their colossal magnetoresistance (a dramatic change in electrical resistance under a magnetic field). Traditionally, scientists modelled this behaviour by treating the localized spins as classical arrows \u2014 big and well-defined, like compass needles. This approximation works well enough for explaining basic ferromagnetism, but experiments over the last few decades have revealed strange features that defy the classical picture. In particular, neutron scattering studies of manganites showed that the collective spin excitations, called magnons, do not behave as expected. Their energy spectrum \u201csoftens\u201d (the waves slow down) and their sharp signals blur into fuzzy continua \u2014 a sign that the magnons are losing their coherence. Until now, these effects were usually blamed on vibrations of the atomic lattice (phonons) or on complex interactions between charge, spin, and orbital motion.<\/p>\n

\"2025-november-researchgroup-Herbrych\"<\/a>Left to right: Adriana Moreo and Elbio Dagotto from University of Tennessee (USA), Takami Tohyama from Tokyo University of Science (Japan), and Marcin Mierzejewski and Jacek Herbrych from Wroc\u0142aw University of Technology (Courtesy: Herbrych\/Wroc\u0142aw University of Science and Technology)<\/p>\n

A new theoretical study challenges that assumption. By going fully quantum mechanical \u2014 treating every localized spin not as a classical arrow but as a true quantum object that can fluctuate, entangle, and superpose \u2014 the researchers have reproduced these puzzling experimental observations without invoking phonons at all. Using two powerful model systems (a quantum version of the Kondo lattice and a two-orbital Hubbard model), the team simulated how electrons and spins interact when no semiclassical approximations are allowed. The results reveal a subtle quantum landscape. Instead of a single type of electron excitation, the system hosts two. One behaves like a spinless fermion \u2014 a charge carrier stripped of its magnetic identity. The other forms a broad, \u201cincoherent\u201d band of excitations arising from local quantum triplets. These incoherent states sit close to the Fermi level and act as a noisy background \u2014 a Stoner-like continuum \u2014 that the magnons can scatter off. The result: magnons lose their coherence and energy in just the way experiments observe.<\/p>\n

Perhaps most surprisingly, this mechanism doesn\u2019t rely on the crystal lattice at all. It\u2019s an intrinsic consequence of the quantum nature of the spins themselves. Larger localized spins, such as those in classical manganites, tend to suppress the effect \u2014 explaining why decoherence is weaker in some materials than others. Consequently, the implications reach beyond manganites. Similar quantum interplay may occur in iron-based superconductors, ruthenates, and heavy-fermion systems where magnetism and superconductivity coexist. Even in materials without permanent local moments, strong electronic correlations can generate the same kind of quantum magnetism.<\/p>\n

In short, this work uncovers a purely electronic route to complex magnetic dynamics \u2014 showing that the quantum personality of the electron alone can mimic effects once thought to require lattice distortions. By uniting electronic structure and spin excitations under a single, fully quantum description, it moves us one step closer to understanding how magnetism truly works in the most intricate materials.<\/p>\n

Do you want to learn more about this topic?<\/p>\n

Nanoscale electrodynamics of strongly correlated quantum materials<\/a> by Mengkun Liu,\u00a0Aaron J Sternbach\u00a0and\u00a0D N Basov\u00a0(2017)<\/p>\n","protected":false},"excerpt":{"rendered":"New research reveals how quantum effects in double-exchange ferromagnets drive unexpected magnetic behaviour Iron-based material (Courtesy: iStock\/Assistantua) For…\n","protected":false},"author":2,"featured_media":273134,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[49],"tags":[199,79],"class_list":{"0":"post-273133","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-physics","8":"tag-physics","9":"tag-science"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/273133","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/comments?post=273133"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/273133\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media\/273134"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media?parent=273133"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/categories?post=273133"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/tags?post=273133"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}