uu.seUppsala University Publications
Change search
ReferencesLink to record
Permanent link

Direct link
Magnetic and transport properties of Ni81Fe19/Al2O3 granular multilayers approaching the superparamagnetic limit
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Chalmers tekniska högskola.
Chalmers tekniska högskola.
Chalmers tekniska högskola.
Show others and affiliations
2007 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, no 7, 073907- p.Article in journal (Refereed) Published
Abstract [en]

The magnetic and transport properties of Ni81Fe 19/Al2O3 granular multilayer films were studied in relation to their structural properties as the nominal thickness t of the permalloy (Ni81Fe19) layer was varied near the percolation limit: in the range of 8≤t≤ 16 Å while keeping the nominal thickness of the Al2O3 layers constant at 16 Å. A good structural quality of the multilayers was demonstrated by low angle x-ray reflectivity measurements, and transmission electron microscopy showed the transition from continuous permalloy layers separated by aluminium oxide layers for t= 16 Å to metal grains dispersed in the insulator at t=8 Å. Magnetization measurements showed the gradual transition from ferromagnetic layers to superparamagnetic clusters and grains that successively become blocked as the temperature decreases. A strong correlation between transport and structural properties was observed in the temperature (T) dependence of the electrical resistance measured with the current in the plane in the range of 2 ≤T≤300 K: a gradual change of behavior from continuous permalloy layers with conducting interlayer connections for t=16 Å. to isolated permalloy grains in a dielectric for the film with t= 10 Å. The percolation occurs between 12 and 10 Å, as deduced both from the magnetic and resistive properties. The discontinuous metal films were analyzed within models for thermally assisted tunneling, yielding estimates of the tunneling barrier for intralayer conduction of about 20 meV for t= 10 Å. A significant magnetic field dependence of the resistance increasing with decreasing temperature was observed in all samples.

Place, publisher, year, edition, pages
2007. Vol. 101, no 7, 073907- p.
Keyword [en]
Permalloy, aluminium compounds, magnetic multilayers, percolation, X-ray reflection, transmission electron microscopy, ferromagnetic materials, superparamagnetism, galvanomagnetic effects
National Category
Physical Sciences Engineering and Technology
URN: urn:nbn:se:uu:diva-10705DOI: 10.1063/1.2715740ISI: 000245691000056OAI: oai:DiVA.org:uu-10705DiVA: diva2:38473
Available from: 2007-04-20 Created: 2007-04-20 Last updated: 2016-04-11Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Hjörvarsson, BjörgvinLidbaum, HansLeifer, Klaus
By organisation
Solid State PhysicsDepartment of PhysicsExperimental PhysicsApplied Materials Sciences
In the same journal
Journal of Applied Physics
Physical SciencesEngineering and Technology

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 429 hits
ReferencesLink to record
Permanent link

Direct link