Ferromagnetic resonance, magnetic susceptibility, and transformation of domain structure in CoFeB film with growth induced anisotropy
2011 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 109, no 8, 083926- p.Article in journal (Refereed) Published
Field dependence of magnetic susceptibility in nanocrystalline CoFeB film was studied in a wide frequency range from 500 kHz to 15 GHz. Anomalies of the susceptibility were detected exciting CoFeB film with a solenoidal coil, microwave strip line, in the tunable microwave cavity as well as employing magneto-optical domains imaging. Critical spin fluctuations in the form of "soft" modes were observed in a whole range of orientations of magnetic field perpendicular to the "easy" magnetic axis. A sequence of domain structure transformations was extensively examined in a "hard" direction in in-plane magnetic field reduced below the field of uniaxial anisotropy H-p = 535Oe. At first, uniformly magnetized state in CoFeB film transforms to stripe domains separated by low angle Neel domain walls (DWs) parallel to the "hard"-axis. Then, at critical field H-cr = 232 Oe, Neel DWs gradually convert to the"easy"-axis oriented Bloch DWs loaded with vertical Bloch lines (VBLs). After field reversal at H = H-cr, backward conversion of VBL-loaded Bloch DWs to Neel DWs results in instantaneous energy release and sharp anomaly of magnetic susceptibility. Appearance of critical spin fluctuations accomplishes domains transformation to the uniformly magnetized state at H = 535 Oe.
Place, publisher, year, edition, pages
2011. Vol. 109, no 8, 083926- p.
IdentifiersURN: urn:nbn:se:kth:diva-33972DOI: 10.1063/1.3559732ISI: 000290047000118ScopusID: 2-s2.0-79955710753OAI: oai:DiVA.org:kth-33972DiVA: diva2:419955
QC 201105302011-05-302011-05-232011-11-22Bibliographically approved