Fe-Based Magnetic Alloy Electrodeposition for Thin Films and Template Based Nanostructures

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 contribution 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 Fe 70 Pd 30 alloy exhibits the magnetic shape memory effect. The Fe-Pt L1 0 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 are discussed based on quartz microbalance experiments. Deposition 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. [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