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Magnetisation Behaviour of Transition Metals and Ferrites

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Within this dissertation, an examinatio of ferro-, ferri-, and paramagnetic fields and how they all behave distinctly and how the level of magnetism of an object can be measured using a superconducting quantum interfering device (SQUID), the Magnetic Optical Kerr Effect (MOKE), or a Vibrating Sample Magnetometer (VSM) will be examined. The use of Giant Magneto-Resistance (GMR) as a technological advancement with numerous applications within the technological industry that applies magnetic fields to every day appliances and objects will also be examined. The use of the Stoner-Wohlfarth Theory, which assumes samples have a single domain to predict the hysteresis loop, will be presented with an accompanying proof and the results of an experiment using a VSM will be presented. The presented data will detail the magnetic behaviours of ferrites and transition metals.

The focus of this dissertation is to discuss the behaviour of ferrites and transition metal alloys when they are magnetised. Ferrites are ferromagnetic materials (Kazimierczuk, 2009). Ferromagnetic substances are materials which acquire strong magnetic properties following the direction of the applied field when exposed to a magnetic field. The property demonstrated by ferromagnetic substances, such as iron, nickel, cobalt, steel, gadolinium and their corresponding alloys are termed as ferromagnetism. (Prakash, 2009). Transition metals are the metallic elements that serve as a bridge, or transition, between the two sides of the periodic table of elements and are located in groups IB through VIIIB. The transition elements are known as the transition metals because they possess the properties of metals in that these elements are very hard, with high melting and boiling points. Additional characteristics of transition metals are that they have several oxidation states, they usually form coloured compounds, and they are often paramagnetic. The transition elements include the important metals iron, copper and silver, although iron and titanium are the most abundant transition elements and the majority of catalysts for industrial reactions involve transition elements. Magnetisation refers to the exposure of a metal to a magnetic field causing the metal to be magnetised with the level of magnetism being a function of the strength of the magnetic field (Cullity and Graham, 2009). In a more technical sense, magnetisation was described by Lalena and Cleary (2010)