Electrodeposition and Properties of Fe-Based Magnetic Alloys 1341 views

The goal of this work was to apply and extend a citrate-glycine complex of ferric ions based alkaline solution to generate a range of Fe-based alloy electrodeposits and nanostructures that could not be obtained otherwise. From a series of electrochemical experiments and characterization performed, electrolytes producing uniform Fe-based alloys with desired magnetic properties were achieved and reported. Systematic studies were carried out on binary (FeNi and FePt) and ternary (FeNiPt) iron group alloys relating their structure, magnetic properties with composition, thickness and annealing conditions. Fabrication of L10-FePt nanodot arrays for bit patterned media (BPM) by electrodeposition from an alkaline solution was described, with an ultimate goal to achieve isolated bits of size ~10nm. In this thesis, a nanoimprinting technique was employed to form patterned substrate with 150nm pitch by collaborating with colleagues at Waseda University, Japan. Deposition and annealing conditions for FePt nanopatterns were studied and optimized. In particular, a patterned Fe48Pt52 (55nm) with a high coercivity of around 8.2kOe was formed by electrodeposition with subsequent heat treatment, demonstrating the capability of electrochemical processes to produce high performance FePt ferromagnetic nanodot arrays. Electrodeposition of Fe-Ni-Pt thin films for applications in heat-assisted magnetic recording (HAMR) was also studied. An electrolyte based on the citrate-glycine complexes of ferric ions for the deposition process was investigated and optimized to generate a series of homogeneous FexNi50-xPt50 (0<x<30) thin films. Anomalous deposition phenomenon was observed and described for different deposition baths. Magnetic properties dependence on Ni content and annealing temperatures were analyzed and discussed. We reported a Fe42Ni12Pt46 thin film with a coercivity of 8.8kOe after annealing at 700oC and its temperature dependence of magnetic properties, which turned out to be suitable for the writing performance of recording media. As a soft magnetic material, permalloy (Fe19Ni81) found many applications in areas such as magnetic recording heads or magnetic field sensors. Electrodeposition from an alkaline solution was applied for the first time to obtain permalloy or Pt-doped permalloy thin film alloys with coercivities lower than 10Oe. Pt addition to the permalloy is expected to enhance the damping effect and fasten magnetization switching, resulting in higher speed or data rates for the magnetic recording. The anomalous deposition phenomenon was observed and discussed. From the same solution, equiatomic FeNi thin films were also obtained, followed by heat treatment to explore the possibility to form tetragonal L10-FeNi in laboratory conditions.

MS (Master of Science)

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2015-07-10