  Magnetic anisotropy is a fundamental property of magnetic materials that
determines the alignment of the spins along the preferential direction, called
the easy axis of magnetization. Magnetic polycrystalline thin films offer
several advantages over magnetic epitaxial thin films because of fabrication
flexibility, higher coercivity and improved magnetic stability, higher
magnetoresistance (useful in magneto-resistive devices such as magnetic field
sensors and MRAM cells), cost-effectiveness and thermal stability, etc. In the
case of polycrystalline thin films or multilayers, Magneto-crystalline
anisotropy (MCA) is not expected due to the random orientation of grains.
Therefore, understanding the origin of uniaxial magnetic anisotropy (UMA) is
generally difficult and can't be understood in terms of crystal orientation.
The origin of UMA in polycrystalline films is often related to the preparation
conditions and substrate properties. In the present thesis, we have provided
direct in-situ real-time evidence of the stress dependence of magnetic
anisotropy through the multibeam optical stress sensor (MOSS) technique. Also,
we have tuned the magnetic anisotropy in strength and direction using
externally applied stress. To further increase the strength of the magnetic
anisotropy, we have developed a new technique that creates a multilayer using a
single magnetic material through sequential oblique and normal depositions.
This oblique angle deposition technique also helps reduce the penetration of
the top ferromagnetic layer inside the organic semiconductor layer in organic
spin valve structures. We confirm our results through various in-situ (in UHV
and HV) and ex-situ temperature-dependent conventional and unconventional
structural, morphological, and magnetic measurements (both lab-based and
synchrotron-based) that include MOKE, KERR, GIXRD, AFM, RHEED, and GISAXS, etc.
measurements.
