Interlayer Coupling in Co/Al2O3 multilayers
N Chowdhury1, S Bedanta1*, G S Babu1
1
School of Physical Sciences, National Institute of Science Education and Research (NISER), IOP Campus,
Bhubaneswar-751005, India
*
Corresponding author’s e-mail: sbedanta@niser.ac.in, Tel.: + 91-674-2304095
We show that inter-layer coupling interactions lead to
layer-by-layer reversal in the magnetic multilayers.
Longitudinal magneto-optic Kerr microscopy (LMOKE)
has been performed on [Co(10nm)/Al2O3(t)/Co(10nm)] for
various thicknesses of Al2O3(t). For low thickness of Al2O3,
the Co layers exhibit only longitudinal component of
magnetization. But for higher thickness of Al2O3
transverse component along with longitudinal component
of magnetization was observed.
magnetization reversal and domain images for
[Co(10nm)/Al2O3(2nm)/Co(10nm)]. For systems with
higher thickness of the spacer layer (N) in
[Co(10nm)/Al2O3(t)/Co(10nm)], transverse component
of magnetization was observed.
Keywords: Magnetic thin film, Magneto – Optic Kerr effect
microscopy, Interlayer coupling, Magnetization reversal,
Magnetic domains.
With the discovery of Giant Magneto
resistance effect [1], magnetic thin films have been a
subject of intense research for both physicists and
engineers in last few decades. From a technological
point of view, magnetic ultrathin and thin films are
potential for use in high-density data storage, magnetic
sensing and magnetoelectronic applications. However
apart from these applications, magnetic thin films are
excellent system for studying fundamental physics such
as inter-layer coupling, magnetic domains and domain
wall dynamics. In magnetic multilayers where
ferromagnetic layers (F) are separated by non-magnetic
layers (N), F/N/F can have different kind of interactions
depending on the nature of nonmagnetic spacer. For
ferromagnetic layers separated by metallic spacer,
depending on the thickness of the spacer layer,
exchange coupling shows oscillatory behavior due to
RKKY coupling [2]. But for insulating spacers it shows
non oscillatory monotonically decreasing behavior [3].
In this presentation, We show the effect of
interlayer coupling on the magnetization reversal
processes of two cobalt layers with the same thickness
separated by an insulating layer of Al2O3. The thickness
of the spacer layer i.e. Al2O3 was varied to study the
effect of coupling. Kerr microscopy was performed for
magnetic hysteresis and simultaneous imaging of
domains of the two Cobalt layers. Uniaxial anisotropy
induced by oblique deposition was observed in all the
samples [4]. We observe that inter-layer coupling
interactions lead to layer-by-layer reversal in the
magnetic multilayers [5]. Figure1 shows the
Fig. 1: Hysteresis loop and domain images taken by
Kerr Microscope for Co(10nm)/Al2O3(2nm)/Co(10nm)
Acknowledgment
We thank National Institute for Science
Education and Research (NISER) and the Department
of Atomic Energy of the Government of India for the
financial support.
References
[1] P. Grunberg, R. Schreiber, and Y. Pang, “Layered
Magnetic Structures: Evidence for Antiferromagnetic
Coupling of Fe Layers across Cr Interlayers”, Phys.
Rev. Lett., 57, 19, (1986).
[2] S. S. P. Parkin, “Systematic Variation of the
Strength and Oscillation Period of Indirect Magnetic
Exchange Coupling through the 3d, 4d, and 5d
Transition Metals”, Phys. Rev. Lett, 67, 25, (1991).
[3] J.F. Vincent et al. “Interlayer Magnetic Coupling
Interactions of Two Ferromagnetic Layers by Spin
Polarized Tunneling”, Phys. Rev. Lett, 89, 10, (2002).
[4] N. Chowdhury and S. Bedanta, “Controlling the
anisotropy and domain structure with oblique deposition
and substrate rotation”, AIP Advances, 4, 2 (2014)
[5] N. Chowdhury, S. Bedanta and S. Babu (to be
communicated)