Unit:
Κατεύθυνση Τεχνολογίας Ολοκληρωμένων ΚυκλωμάτωνΠληροφορική
Author:
Koutsouflakis Emmanouil
Supervisors info:
Αγγελική Αραπογιάννη, Καθηγήτρια, Τμήμα Πληροφορικής & Τηλεπικοινωνιών
Δημήτριος Νιάρχος, Ομότιμος Ερευνητής Ε.Κ.Ε.Φ.Ε. "Δημόκριτος"
Ανδρέας Καϊδατζής, Μεταδιδακτορικός Ερευνητής Ε.Κ.Ε.Φ.Ε. "Δημόκριτος"
Original Title:
Μελέτη σκληρών μαγνητικών λεπτών υμενίων FeNi μέσω τεχνικών συσχέτισης δομής, μορφολογίας και μαγνητικών ιδιοτήτων
Translated title:
Study of hard thin magnetic FeNi films via correlation techniques of structure, morphology and magnetic properties
Summary:
L10-type magnetic compounds, including FeNi, possess promising technical magnetic properties of both high magnetization and large magnetocrystalline anisotropy energy and thus offer potential in replacing rare earth permanent magnets in some applications. L10-FeNi was first discovered in an iron meteorite, formed by the long-range thermal diffusion of Fe and Ni in an asteroid’s core over a period of 4.6 billion years. It was first artificially made in the L10-type structure with a stoichiometry of Fe50Ni50 by neutron bombardment and estimated the order-disorder transformation temperature to be around 3200C, which is very low compared to the other L10-alloys. This results in very low diffusion of Fe and Ni atoms and makes the transformation extremely sluggish. This transformation can be enhanced either by the creation of vacancies, core-shell FeNi/L10-AuCu nanoparticles, or in the case of thin films by a strain mediated process.
In this work, we have employed a combinatorial sputtering process in order to study the conditions of fabricating the L10-FeNi phase and measure its magnetic properties. We have used Si (100) 100 mm wafers as substrates and deposited multilayers of the following type: Si/ Cr(10 nm)/ Cu3Au(70 nm)/combi - CuAuNi/NiFe(40 nm), where combi-CuAuNi is a compositional spread layer of various stoichiometries deposited using combinatorial sputtering, to match the lattice constants of the L10-FeNi. The rest of the layers have homogeneous composition and thickness. The final deposition of FeNi was done at 2000C by co-sputtering Fe and Ni to a stoichiometry of 50/50 at%. We perform magnetic properties mapping of the multilayer by means of high-throughput polar Kerr effect magnetometry and we find that the coercivity increases from approximately 0.3 kOe to 1 kOe as the Au content of the combinatorial interlayer decreases. A thorough structural and magnetic properties study will be presented.
Main subject category:
Science
Keywords:
magnetization, coercivity, ferromagnetism, atomic force microscopy, island growth
