Thin film quantum materials

Abstract:

The University of Waterloo, Waterloo, ON, Canada, is home to North America's first undergraduate program in nanotechnology. As part of the Nanotechnology Engineering degree program, a scanning probe microscopy (SPM)-based laboratory has been developed for students in their fourth year. The one-term laboratory course Nanoprobing and Lithography is accompanied by a preceding one-term lecture course, Nanoprobing and Lithography. The lecture course lays the theoretical foundation for the concepts covered in the laboratory course. The students work in groups of two and obtain hands-on experience in biweekly 3-h laboratory sessions. The labs use a dedicated undergraduate SPM teaching facility consisting of five atomic force microscope stations. The laboratory course covers all common standard modes of operation, as well as force spectroscopy, electrostatic force microscopy, magnetic force microscopy, and scanning probe lithography by electrochemical oxidation and scratching/ploughing of resist. In light of the breadth of the nanotechnology engineering educational program in terms of synthesis and characterization of nanomaterials, the authors designed a dedicated SPM lab with a capacity of up to 130 students per term. © 2010 IEEE.

Abstract:

V-shaped domain transitions in αMnAs nanowires were investigated by micromagnetic simulations. These rather unusual domain patterns are commonly observed experimentally by surface-sensitive magnetic imaging techniques. It has been speculated that the accompanying inclined domain walls in MnAs are the result of either an exchange biasing effect between ferromagnetic αMnAs wires and antiferromagnetic βMnAs wires or possibly due to competing exchange mechanisms in MnAs. Here we present evidence that these domain features are in fact transitions between three-dimensional flux-closure domains of opposite chirality and can therefore rule out the involvement of an antiferromagnetic biasing effect or anisotropic exchange. The formation of the energetically unfavorable V-shaped domain transitions is discussed in the context of the magneto-structural phase transition of the sample. © 2011 Elsevier B.V.