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Effects of substitution on the exchange stiffness and magnetization of Co films
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
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2014 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 90, no 23, 235408- p.Article in journal (Refereed) Published
Abstract [en]

An antiferromagnetically coupled FM/NM/FM (FM = ferromagnet, NM = normal metal) trilayer structure responds to an external magnetic field by the formation of a magnetic-moment spring within the FM layers. We show that the exchange stiffness (A ex) of an FM layer can be determined by fitting the field-dependent magnetization, M(H), of the FM/NM/FM trilayer to a micromagnetic model. Using this method, we have measured the exchange stiffness of thin-film Co alloyed with Cr, Fe, Ni, Pd, Pt, and Ru. The results show that the rate at which a substituent element reduces the exchange stiffness is not directly related to its effect on the magnetization of the alloy. The observed trends have been understood by material-specific modeling based on density functional theory within the local density approximation. The stiffness measurements are in agreement with Brillouin light scattering carried out on thicker Co films.

Place, publisher, year, edition, pages
2014. Vol. 90, no 23, 235408- p.
National Category
Physical Sciences
URN: urn:nbn:se:uu:diva-239091DOI: 10.1103/PhysRevB.90.235408ISI: 000348846500002OAI: oai:DiVA.org:uu-239091DiVA: diva2:775930
Available from: 2015-01-05 Created: 2014-12-18 Last updated: 2015-04-29Bibliographically approved
In thesis
1. Metallic Amorphous Thin Films and Heterostructures with Tunable Magnetic Properties
Open this publication in new window or tab >>Metallic Amorphous Thin Films and Heterostructures with Tunable Magnetic Properties
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The primary focus of this thesis is to study the effect of doping on magnetic properties in amorphous Fe100−xZrx alloys. Samples with compositions of x = 7,11.6 and 12 at.% were implanted with different concentrations of H. Moreover, the samples with a composition of x = 7 at.% were also implanted with He, B, C and N. Magnetic measurements were performed, using SQUID magnetometry and MOKE, in order to compare the as-grown and the implanted films. The Curie temperature (Tc) increases and the coercivity (Hc) decreases, with increasing dopant volume. We also found that Hc increases with temperature for B and C doped samples. Magnetization curves at low temperature validate the presence of non-collinear spin configurations in the as-grown films, which is suppressed after doping, resulting in films with tunable soft magnetic properties. We have also studied the effect of interlayer mixing and finite size effects on FeZr in Fe92Zr8/AlZr multilayer films, and found an anomalous increase of Tc with decreasing thickness.

Strain induced changes in the magnetization of an amorphous Co95Zr5 film at the orthorhombic phase transition of the BaTiO3 substrate, was also studied. The results show that structural modifications of the substrate increases the stress and hence changes the magnetic anisotropy in the amorphous Co95Zr5 layer.

Finally, the magnetization reversal of Co and CoX heterostructures, with X being Cr, Fe, Ni, Pd, Pt and Ru, has been studied. For this purpose a synthetic antiferromagnet structure, FM/NM/FM, was used, where FM is a ferromagnetic Co or CoX layer and NM is a nonmagnetic Ru spacer layer. The FM layers are coupled antiferromagnetically across the NM layer. For a range of FM layer thicknesses, the exchange stiffness parameter Aex and the interlayer coupling (JRKKY ) of the Co or CoX layers were obtained. This is done by fitting M(H) curves, measured by SQUID magnetometry, to a micromagnetic model. The alloying in CoX resulted in a decreasing Aex and also a reduced MS. The experimental results are in a good agreement with DFT calculations.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 60 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1218
Amorphous, Thin Film, Magnetic properties, FeZr alloys, Ion implantation
National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
urn:nbn:se:uu:diva-239950 (URN)978-91-554-9139-0 (ISBN)
Public defence
2015-02-27, 10134, Ångströmlaboratoriet, Polacksbacken, Uppsala, 10:15 (English)
Available from: 2015-02-06 Created: 2015-01-04 Last updated: 2015-03-09Bibliographically approved

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Zamani, AtiehAhlberg, MartinaKaris, OlofJönsson, Petra E.
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