Pub Date : 2025-01-20DOI: 10.1109/LMAG.2025.3531777
Frederik L. Durhuus;Theis H. van Bijlevelt Rix;Maciej A. Głód;Marco Beleggia;Cathrine Frandsen
Understanding thermal relaxation effects in magnetic nanoparticle (MNP) systems is key to several imaging techniques and clinical applications. Here, we consider the Néel relaxation of compact MNP clusters, using Langevin dynamics simulations to compute the relaxation time as a function of magnetostatic coupling strength. By also analyzing individual thermal reversals, we establish connections between the magnetic structure of a cluster and its Néel relaxation time. In particular, faster relaxation and more exotic behavior are observed for 3-D clusters with several nearly degenerate states, as the magnetization intermittently jumps to metastable states, which can facilitate reversal. Conversely, aggregates with many moments in a single flux-closed loop exhibit fewer metastable states and are efficiently blocked by strong dipole coupling.
{"title":"Néel Relaxation of Magnetic Nanoparticle Clusters","authors":"Frederik L. Durhuus;Theis H. van Bijlevelt Rix;Maciej A. Głód;Marco Beleggia;Cathrine Frandsen","doi":"10.1109/LMAG.2025.3531777","DOIUrl":"https://doi.org/10.1109/LMAG.2025.3531777","url":null,"abstract":"Understanding thermal relaxation effects in magnetic nanoparticle (MNP) systems is key to several imaging techniques and clinical applications. Here, we consider the Néel relaxation of compact MNP clusters, using Langevin dynamics simulations to compute the relaxation time as a function of magnetostatic coupling strength. By also analyzing individual thermal reversals, we establish connections between the magnetic structure of a cluster and its Néel relaxation time. In particular, faster relaxation and more exotic behavior are observed for 3-D clusters with several nearly degenerate states, as the magnetization intermittently jumps to metastable states, which can facilitate reversal. Conversely, aggregates with many moments in a single flux-closed loop exhibit fewer metastable states and are efficiently blocked by strong dipole coupling.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"16 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143512878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-13DOI: 10.1109/LMAG.2024.3497794
Sheetal Yadav;Monika Sharma;Bijoy K. Kuanr
Magnon–photon hybrid systems have potential applications in quantum information processing. The spatial distribution of magnetic field intensity plays a crucial role in enhancing coupling strength. We have investigated strong magnon–photon coupling using a planar waveguide with defects in the ground for dual-frequency ranging from S to C band. Dual inverted split ring resonators were used as a photon resonator, and a yttrium iron garnet (YIG) pellet acted as a magnon source. The interaction between magnon and photon modes was manipulated by variations in the spatial distribution of the magnetic field along the microstrip line. The ferrite sample was placed at three different positions, viz., A, B, and C. The coupling strength $g$