Researcher to Give Seminar on Iron-Based Alloys for Thin Films and Nanostructures

Veronika Haehnel, a researcher at the Leibniz Institute for Solid State and Materials Research in Dresden, Germany, will offer a seminar on "Electrodeposition of Fe-Based Magnetic Alloys for Thin Films and Template Based Nanostructures" at 3:30 p.m. Friday, Oct. 14, in Chemistry Building room 144.

Refreshments will be offered before the lecture at 3:15 in CHEM 133.

Haehnel works as a scientific staff member at Leibniz Institute in the Institute for Complex Materials. Her research involves tailored manipulation of fluids in highly functionalized, highly integrated micro-and nanoscale fluidic systems.

From 2009-2014, she served as a scientific staff member in the Institute for Metallic Materials at Leibniz-IFW studying preparation and characterization of magnetic thin films and nanowires. During that time, she was a DAAD-Scholar at the University of Bristol, England, using scanning tunneling microscopy to investigate electrochemical processes. She received her Diploma and Doctorate in Materials Science from the Dresden University of Technology. She also trained at the University of York in England in Liquids Research in the area of advanced nanoparticles for magnetic data storage media.

Abstract: Iron based alloys exhibit extraordinary material and magnetic properties. They are of fundamental scientific interest, e.g. as smart and intelligent materials for magnetic storage, recording, sensing or actuating. There is an increasing importance of technical applications due to ongoing omnipresent miniaturization and integration in MEMS/NEMS systems. The dimension and geometry of the material can be tailored towards thin films, nanowires or advanced nanostructures generating high functionality for various purposes.

To meet demands in miniaturization and performance of electronic devices, often low dimensional structures with highly complex geometries are requested. Electrodeposition is the most appropriate, cost and time efficient method for the fabrication of well-ordered nanoscaled structures and in particular to produce high aspect ratio nanowires. The preparation of nanoscaled magnetic materials such as Co, Fe and Ni in porous templates is a well known standard procedure[1-3]. Magnetic alloys or multilayers with specific magnetic properties are still of increasing interest. Compared to single metal deposition a more precise control of the respective electrolyte composition and deposition parameters is needed. Alloy deposition is often restrained by a strong difference in deposition potentials of the respective components. In reduced dimensions transport conditions and therefore, deposition kinetics are crucial for a successful plating process, too.

This talk focusses on the electrochemical preparation of Fe-based magnetic alloys such as Co-Fe, Fe-Ga, Fe-Pd and Fe-Pt. CoFe alloys are well known for tremendous soft magnetic properties with high saturation polarization of up to 2.4 T. A high magnetostriction is achieved in Fe-Ga alloys with 80 at.% Fe. The Fe70Pd30 alloy exhibits the magnetic shape memory effect. The Fe-Pt L10 phase shows good hard magnetic behavior due to high magnetocrystalline anisotropy and a high saturation magnetization. Therefore these alloys are very promising candidates for smart and intelligent materials in the fields of actuating or sensing or as micromagnets in MEMS.

For the Co-Fe system simple sulfate based electrolytes and potentiostatic deposition[4] as well as alternating potential regimes are most efficient. The more challenging systems Fe-Ga, Fe-Pd [5,6] and Fe-Pt require advanced complexed electrolytes. Deposition mechanisms and parameters are systematically investigated with regard to compact defect free deposits with homogeneous composition distribution. The correlation of electrolyte composition and deposition regime with deposit structure, morphology and magnetic properties is discussed.

References: [1] Schlörb et al., Phys. Status Solidi B 247, 2010, 2463; [2] Haehnel et al., Acta Mater. 58, 2010, 2330; [3] Nielsch et al., Adv. Mater. 12, 2000, 582; [4] Vock et al., J. Appl. Phys. 118, 2015, 233901; [5] Iselt et al., J. Electrochem. Soc. 159, 2012, H633; [6] Konczak et al., Mater. Chem. Phys. 174, 2016, 150.