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Magnetic properties of wurtzite (Ga,Mn)As
Polish Academy of Sciences, Poland.
Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Polish Academy of Sciences, Poland.ORCID iD: 0000-0002-9495-2648
Polish Academy of Sciences, Poland.
2021 (English)In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 533, article id 168012Article in journal (Refereed) Published
Abstract [en]

Here we report on detailed studies of the magnetic properties of the wurtzite (Ga,Mn)As cylindrical shells. Ga0.94Mn0.06As shells have been grown by molecular beam epitaxy at low temperature as a part of multishell cylinders overgrown on wurtzite (Ga,In)As nanowires cores, synthesized on GaAs (111)B substrates. Our studies clearly indicate the presence of a low temperature ferromagnetic coupling, which despite a reasonably high Mn contents of 6% is limited only to below 30 K. A set of dedicated measurements shows that despite a high structural quality of the material the magnetic order has a granular form, which gives rise to the dynamical slowdown characteristic to blocked superparamagnets. The lack of the long range order has been assigned to a very low hole density, caused primarily by numerous compensation donors, arsenic antisites, formed in the material due to a specific geometry of the growth of the shells on the nanowire template. The associated electrostatic disorder has formed a patchwork of spontaneously magnetized (macrospin) and nonmagnetic (paramagnetic) volumes in the material. Using high field results it has been evaluated that the total volume taken by the macrospins constitute about 2/3 of the volume of the (Ga,Mn)As whereas in the remaining 1/3 only paramagnetic Mn ions reside. By establishing the number of the uncoupled ions the two contributions were separated. The Arrott plot method applied to the superparamagnetic part yielded the first experimental assessment of the magnitude of the spin-spin coupling temperature within the macrospins in (Ga,Mn)As, TC = 28 K. In a broader view our results constitute an important contribution to the still ongoing dispute on the true and the dominant form(s) of the magnetism in this model dilute ferromagnetic semiconductor.

Place, publisher, year, edition, pages
Elsevier, 2021. Vol. 533, article id 168012
Keywords [en]
Magnetic semiconductor nanowires, Core-shell structures, Wurtzite (Ga, Mn)As, Molecular beam epitaxy, Magnetic properties, Superparamagnetism
National Category
Condensed Matter Physics Nano Technology
Research subject
Physics, Condensed Matter Physics
Identifiers
URN: urn:nbn:se:lnu:diva-104070DOI: 10.1016/j.jmmm.2021.168012ISI: 000649634400007Scopus ID: 2-s2.0-85105693257Local ID: 2021OAI: oai:DiVA.org:lnu-104070DiVA, id: diva2:1560943
Available from: 2021-06-04 Created: 2021-06-04 Last updated: 2021-06-16Bibliographically approved

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Sadowski, Janusz

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