Date of Graduation

Spring 2018

Degree

Master of Science in Materials Science

Department

Physics, Astronomy, and Materials Science

Committee Chair

Kartik Ghosh

Keywords

ferromagnetism, heterostructures, epitaxial growth, field-dependent magnetic characterization, coercivity

Subject Categories

Materials Science and Engineering

Abstract

Multiferroic heterostructures (MHS) consisting of at least two materials with ferroic properties have been a major focus for researchers recently due to its immense potential in device applications. Almost all MHS use ferromagnetic layers making it a very important research area. In this thesis the magnetic properties of different ferromagnetic heterostructures have been investigated. Different bilayers of hard ferromagnet cobalt ferrite (CFO)-soft ferromagnet lanthanum strontium manganese oxide (LSMO) and hard ferromagnet CFO-antiferromagnet nickel oxide (NiO) were fabricated. Pulsed laser deposition technique was used to deposit the thin films on LAO and sapphire substrates. Purpose of using a hard ferromagnetic CFO thin film on top of soft ferromagnetic LSMO and antiferromagnetic NiO was to enhance the multiferroic effects. X-ray diffraction (XRD) analysis on different samples establishes the epitaxial growth of the thin films. Transmission electron microscope (TEM) and scanning electron microscope (SEM) analysis provide the structural and elemental composition of the heterostructure. Superconducting quantum interference device (SQUID) magnetometer was used to perform temperature and field-dependent magnetic properties. At room temperature, ferromagnetic hysteresis loop is observed in all MHS. Presence of CFO increases the coercivity of the LSMO thin film which was one of the goals. In addition, I examined the zero field cooled (ZFC) and field cooled (FC) hysteresis curve for the CFO/NiO bilayer and a shift in the FC curve from the ZFC curve is observed. Studies of these different MHS may guide the development of many novel devices such as actuators, transducers and storage devices.

Copyright

© Ahmed Rayhan Mahbub

Open Access

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