Interface and temperature dependent magnetic properties in permalloy thin films and tunnel junction structuresстатья
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Дата последнего поиска статьи во внешних источниках: 24 декабря 2014 г.
Аннотация:Magnetization dynamics and field dependent magnetization of different devices based on 25–30 nm
thick Permalloy (Py) films: such as single Py layers (Py/MgO; Py/CoFeB/Al 2 O 3 and Py inserted
as a magnetic layer in magnetic tunnel junctions (Py/CoFe/Al 2 O 3 /CoFe; Py/CoFeB/Al 2 O 3 /CoFe;
Py/MgO/Fe) have been extensively studied within a temperature range between 300 K down to 2 K.
The dynamic response was investigated in the linear regime measuring the ferromagnetic reso-
nance response of the Py layers using broadband vector network analyzer technique. Both the static
and the dynamic properties suggest the possible presence of a thermally induced spin reorientation
transition in the Py interface at temperatures around 60 K in the all samples investigated. It seems,
however, that the details of the interface between Py and the hardening ferromagnet/insulator struc-
ture, the atomic structure of Py layers (amorphous vs. textured) as well as the presence of dipolar
coupling through the insulating barrier in the magnetic tunnel junction structures could strongly
influence this low temperature reorientation transition. Our conclusions are indirectly supported
by structural characterization of the samples by means of X-Ray diffraction and high resolution
transmission electron microscopy techniques. Micromagnetic simulations indicate the possibility of
strongly enhanced surface anisotropy in thin Py films over CoFe or CoFeB underlayers. Comparison
of the simulations with experimental results also shows that the thermally-induced spin reorientation
transition could be influenced by the presence of strong disorder at the surface.