Abstract
The main idea behind magnonics is to use the elementary magnetic excitations (magnons) for information transfer and processing. One of the main challenges, hindering the application of ultrafast terahertz magnons in magnonics, has been the short lifetime of these excitations in metallic ferromagnets. Here, we demonstrate that the engineering of the electronic structure of a ferromagnetic metal, by reducing its dimensionality and changing its chemical composition, opens a possibility to strongly suppress the relaxation channels of terahertz magnons and thereby enhance the magnons' lifetime. For the first time, we report on the long-lived terahertz magnons excited in ultrathin metallic alloy films. On the basis of the first-principles calculations, we explain the microscopic nature of the long lifetime being a consequence of the peculiar electronic hybridizations of the species. We further demonstrate a way of tailoring magnon energies (frequencies) by varying the chemical composition of the film.
Highlights
The main idea behind magnonics is to use the elementary magnetic excitations for information transfer and processing
One of the main challenges for using terahertz magnons is their short lifetime in metallic ferromagnets[5,6,7,8,9,10,11,12,13,14,15,16]
The strong damping of terahertz magnons in itinerant ferromagnets arises mainly due to the presence of single-particle excitations in the same energy window as the magnons
Summary
The main idea behind magnonics is to use the elementary magnetic excitations (magnons) for information transfer and processing. One of the main challenges, hindering the application of ultrafast terahertz magnons in magnonics, has been the short lifetime of these excitations in metallic ferromagnets. We report on the long-lived terahertz magnons excited in ultrathin metallic alloy films. When a magnon propagates through a magnetic medium, no electrical charge transport is involved and no electrical losses, creating Joule heating, take place This is the fundamental advantage of using magnons as information carriers. If there are no low-energy Stoner excitations, with energies in the range of magnons’ energy, the Landau damping will be inoperative and magnons shall live for a longer time. We report on an alternative material, an ultrathin film of iron–palladium (Fe–Pd) alloy, with a low Landau damping for the potential application in terahertz magnonics. We further demonstrate that the excitation frequencies can be tuned by changing the Fe content in the sample
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