Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 150783

150783 - Magnetic Response of a Core-Shell Composed of Magnetically Different Materials, Ni/cr/cu 

This research investigates an efficient manufacturing method to produce magnetic exchange couplings in core-shell particles made by vibration-assisted high-power impulse magnetron sputtering. With the process of physical vapor deposition, we can deposit more pure materials than other chemical methods that generate by-products, which would taint the results. This approach would potentially advance fields involving magnetism if the theoretical predictions are correct, helping further researchers manufacture these functional materials with clean techniques capable of producing virtually any core-shell composition. The vibration will assist in moving the powder in the sputtering chamber to coat the entire surface of the powder. The case study consists of a Nickel core particle, a ferromagnetic material, with an average diameter of 60 µm. Then shells of Chromium, an antiferromagnetic material, and Copper, a diamagnetic material, are deposited sequentially as thin layers with <100 nm. Research shows that strong couplings occur between Nickel and Chromium, and we are testing what response occurs when a different magnetic material is added to that core-shell. The magnetic moments are measured on the core-shell materials using a vibrating-sample magnetometer at a constant temperature,  293.15 K with a field from -1 T to 1 T,  and at a constant magnetic field of 1 T with a temperature from 50 K to 293.15 K.  Focused ion beam is used to cross-section randomly selected individual particles, as well to cut and prepare lift-out lamellas for transmission electron microscopy. The film growth, microstructure, and thickness of the particles are assessed by scanning electron microscope. Transmission electron microscopy is used to determine core and shell’s structure through selected area electron diffraction and high-resolution transmission electron microscopy, in addition to observing magnetic domains through Lorentz electron microscopy. Preliminary results show changes in the magnetic response of core-shell structures compared with the cores in both constant temperature and constant field. The magnetic moment of the core-shells decreased from 1.3 emu to 1.15 emu at positive saturation, the point where the magnetic moment no longer responds to the magnetic field. The residual magnetism strength also decreased between the two, from 0.04 emu to 0.03 emu. High-resolution X-ray photoelectron spectroscopy peaks of the Ni, Cr, and Cu elements are performed further to correlate the observed magnetic response with the electronic structure. This is interesting, as theoretically, the hysteresis curve representing the magnetic response of the core-shell can be tailored by coating it with materials with varying magnetic properties. This process could then be used to create magnetic couplings in manufacturing facilities to achieve a certain level of magnetism for consumers.q

Presenting Author: Andrew Chernesky Virginia Commonwealth University

Presenting Author Biography: Andrew Chernesky is an undergraduate student in the Mechanical Engineering major at Virginia Commonwealth University. He has attended Virginia Commonwealth University for three years for a Bachelor's in Secondary Education with a Concentration in Engineering. He has recently switched to a Bachelor's in Mechanical Engineering program to align more with his goals in life. He is working towards earning a Ph.D. in Mechanical Engineering to become a college professor in Mechanical Engineering and is on the lookout for what field sparks his passion. Currently, Andrew's research focuses on the magnetic response and coupling of Nickel alloy powders and core-shell structures.

Authors:

Andrew Chernesky Virginia Commonwealth University
Camilo Bedoya Virginia Commonwealth University
Carlos Castano Virginia Commonwealth University