{"id":296654,"date":"2025-11-21T02:04:14","date_gmt":"2025-11-21T02:04:14","guid":{"rendered":"https:\/\/www.newsbeep.com\/ca\/296654\/"},"modified":"2025-11-21T02:04:14","modified_gmt":"2025-11-21T02:04:14","slug":"physicists-just-showed-the-faraday-effect-works-in-a-totally-new-way-after-nearly-200-years","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/ca\/296654\/","title":{"rendered":"Physicists Just Showed the Faraday Effect Works in a Totally New Way After Nearly 200 Years"},"content":{"rendered":"

\"\" <\/a>Illustration of Faraday\u2019s 19th-century experiment. Credit: Enrique Sahag\u00fan.<\/p>\n

In 1845, Michael Faraday showed that light and magnetism are linked. He passed a beam through glass inside a magnetic field and found that its polarization \u2014 the direction its waves wiggle \u2014 rotated. The results of this elegant experiment are known to this day as the Faraday effect. For nearly two centuries, scientists believed they fully understood it: only the electric part of light mattered.<\/p>\n

Not quite so, say physicists at the Hebrew University of Jerusalem. According to their new study, the magnetic component of light \u2014 long dismissed as negligible \u2014 directly contributes to the Faraday effect. \u201cLight doesn\u2019t just illuminate matter, it magnetically influences it,\u201d said Dr. Amir Capua, who co-led the research with Benjamin Assouline.<\/p>\n

The physicists used theoretical modeling to show that light\u2019s oscillating magnetic field can twist the spins of electrons inside materials, producing a measurable change in the way light itself is rotated as it passes through.<\/p>\n

A Forgotten Half of Light<\/p>\n

Light is an electromagnetic wave. You can think of light as a blend of oscillating electric and magnetic fields. Physicists have long focused on the electric half, which shakes charged particles and drives most familiar optical effects. The magnetic half didn\u2019t seem to matter in the Faraday effect.<\/p>\n

\u201cThere is a second part of light that we now understand interacts with materials,\u201d Capua told New Scientist<\/a>. He says researchers overlooked this because magnetic forces in most materials are weaker than electric ones, and because spins \u2014 the quantum sources of magnetism \u2014 often fall out of sync with light\u2019s oscillations.<\/p>\n

But when light is circularly polarized, so its waves twist like a corkscrew, the magnetic component can align more effectively with those spins. Using the Landau\u2013Lifshitz\u2013Gilbert (LLG) equation, which describes how spins behave in a magnetic field, Capua and Assouline showed that this optical magnetic field produces its own magnetic torque \u2014 a twisting force inside the material.<\/p>\n

When they ran their model using a crystal called terbium gallium garnet (TGG), they found that light\u2019s magnetic field accounts for about 17% of the Faraday effect at visible wavelengths, and as much as 70% in the infrared range. <\/p>\n

\u201cOur results show that light \u2018talks\u2019 to matter not only through its electric field, but also through its magnetic field,\u201d said Assouline.<\/p>\n

Shaking Up Magneto-Optics<\/p>\n

The discovery changes how scientists understand the Verdet constant, a number describing how strongly a material rotates light\u2019s polarization under a magnetic field. Traditionally, the Verdet constant has been linked to how the electric component of light interacts with moving charges. But Capua\u2019s team showed that the LLG equation can predict part of that constant using the magnetic component alone. <\/p>\n

Their analysis also revealed something subtler: the Faraday effect and its time-reversed twin, the inverse Faraday effect, aren\u2019t perfect mirror images. In the inverse version, intense light pulses can magnetize materials without any external magnetic field \u2014 essentially flipping spins with light alone. According to the team, the two effects are not exactly reciprocal at ultrafast timescales, because they depend on different kinds of spin dynamics.<\/p>\n

That breakdown of reciprocity could help explain puzzles in ultrafast magnetism \u2014 a field that uses femtosecond laser pulses to control spins for next-generation computing and data storage. <\/p>\n

\u2018\u201cWhat we see is that even when light interacts with matter in incredibly brief bursts, its magnetic component can still play a surprisingly strong role,\u201d Capua said.<\/p>\n

The ability of light to magnetically influence matter could open new paths in spintronics, optical data storage, and even quantum computing, where controlling spin states is key.<\/p>\n

For Capua, the thrill lies in rewriting a chapter of physics that seemed closed. \u201cThe static magnetic field \u2018twists\u2019 the light, and the light, in turn, reveals the magnetic properties of the material,\u201d he said in the Hebrew University press release. \u201cWhat we\u2019ve found is that the magnetic part of light has a first-order effect \u2014 it\u2019s surprisingly active in this process.\u201d<\/p>\n

Still More Work to Do<\/p>\n

For now, Capua and Assouline\u2019s work remains a theoretical breakthrough. But theory alone isn\u2019t proof. No one has yet observed this magnetic influence directly in a lab. The next challenge, says Capua, is designing experiments precise enough to isolate the signal of light\u2019s magnetic torque from the dominant electric one. If confirmed, it would force textbooks to update a law of optics that has stood unchallenged since the 1840s.<\/p>\n

One hundred and eighty years after Faraday glimpsed the bond between light and magnetism, scientists have found the missing half of that partnership \u2014 and it\u2019s been hiding, oscillating, in plain sight.<\/p>\n

The findings appeared in the journal Scientific Reports<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"Illustration of Faraday\u2019s 19th-century experiment. Credit: Enrique Sahag\u00fan. In 1845, Michael Faraday showed that light and magnetism are…\n","protected":false},"author":2,"featured_media":296655,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[24],"tags":[49,48,133525,133526,133527,314,66],"class_list":{"0":"post-296654","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-physics","8":"tag-ca","9":"tag-canada","10":"tag-faraday","11":"tag-faraday-effect","12":"tag-light-polarization","13":"tag-physics","14":"tag-science"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/296654","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/comments?post=296654"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/296654\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media\/296655"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media?parent=296654"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/categories?post=296654"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/tags?post=296654"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}