Magnetic materials are one of the most interesting and promising class of materials for technological applications [1]. Among them, patterned ferromagnetic systems have an important role especially in the prospect of high density data storage [2], domain wall logic devices [3] and magnetic memory [4, 5]. Coupled systems of ferromagnetic and antiferromagnetic materials have been implemented to design sensors such as giant magnetoresistance (GMR) [6-8] and tunnel magnetoresistance (TMR) [9, 10]. Ferromagnetic nanoparticles have been used for the drug targeting, cancer therapy, MRI and many more applications [11, 12]. In addition, more recently, significant attention has been paid to explore the dynamic properties of magnetic materials in the GHz range and use them for technological applications such as microwave filters, signal processing, phase shifter, nonreciprocal microwave devices, spin wave guide, high frequency memory, logic elements [13-19]
Boundary conditions, interactions between individual entities, and lateral confinement of magnetic charges generate diverse magnetic properties especially at nanoscale length [20, 21]. The variation of magnetic properties are even quite different when the size of the magnetic structure is smaller or comparable with the magnetic characteristic length such as mean free path of electron, width of domain wall and even the spin diffusion length [22-24].
In this study, we have considered different magnetic systems. Firstly, the multilayer of coupled ferromagnetic and antiferromagnetic system has been considered to evaluate the exchange bias anisotropy. [FeNi/IrMn]n multilayer systems with different thicknesses of ferromagnetic layer were studied. Static and dynamic properties were revealed through magnetometry measurements (VSM) and VNA-FMR techniques respectively. Angular variation of first order reversal curve (AFORC) and ferromagnetic resonance (AFMR) were performed to learn the intrinsic exchange bias distribution. Secondly, patterned magnetic structures were synthesized to understand the magnetization dynamics in confined geometry. Surface modulated thin films with different periodicity, dumbbell-shaped structures with variable size and three dimensional magnonic crystals have been studied using both static and dynamic measurement techniques. Micromagnetic simulations were performed to understand and explain the experimental results.
| Identifer | oai:union.ndltd.org:uno.edu/oai:scholarworks.uno.edu:td-3508 |
| Date | 09 August 2017 |
| Creators | Khanal, Shankar |
| Publisher | ScholarWorks@UNO |
| Source Sets | University of New Orleans |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | University of New Orleans Theses and Dissertations |
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