Manipulation of magnetic anisotropy in nanostructures

Of late, the magnetic properties of micro/nano-structures have attracted intense research interest both fundamentally and technologically particularly to address the question that how the manipulation in the different layers of nanostructures, geometry of a patterned structure can affect the overall magnetic properties, while generating novel applications such as in magnetic sensors, storage devices, integrated inductive components and spintronic devices. Depending on the applications, materials with high, medium or low magnetic anisotropy and their possible manipulation are required. The most dramatic manifestation in this respect is the chance to manipulate the magnetic anisotropy over the intrinsic preferential direction of the magnetization, which can open up more functionality particularly for device applications. Types of magnetic anisotropies of different nanostructured materials and their manipulation techniques are investigated in this work. Detail experimental methods for the quantitative determination of magnetic anisotropy in nanomodulated Ni45Fe55 thin film are studied. Magnetic field induced in-plane rotations within the nanomodulated Ni45Fe55 continuous films revealed various rotational symmetries of magnetic anisotropy due to dipolar interactions showing a crossover from lower to higher fold of symmetry as a function of modulation geometry. In a second approach, the control of exchange anisotropy at ferromagnetic (FM) – aniferomagnetic (AFM) interface in multifferoic nanocomposite materials, where two different phase/types of materials were simultaneously synthesized, was investigated. The third part of this work was to study the electroplated thin films of metal alloy nanocomposite for enhanced exchange anisotropy. In this work a unique observation of an anti-clock wise as well as a clock wise hysteresis loop formation in the Ni,Fe solid solution with very low coercivity and large positive exchange anisotropy/exchange bias have been investigated. Hence, controllable positive and negative exchange anisotropy has been observed for the first time which has high potential applications such as in MRAM devices.

Ordered magnetic dipoles: controlling anisotropy in nanomodulated continuous ferromagnetic films

In this paper, the research focus is how to entangle magnetic dipoles to control/engineer magnetic properties of different devices at a submicron/nano scale. Here, we report the generation of synthetic arrays of tunable magnetic dipoles in a nanomodulated continuous ferromagnetic film. In-plane magnetic field rotations in modulated Ni 45Fe 55 revealed various rotational symmetries of magnetic anisotropy due to dipolar interaction with a crossover from lower to higher fold as a function of modulation geometry. Additionally, the effect of aspect ratio on symmetry shows a novel phase shift of anisotropy, which could be critical to manipulate the overall magnetic properties of the patterned film. The tendency to form vortex is in fact found to be very small, which highlights that the strong coupling between metastable dipoles is more favorable than vortex formation to minimize energy in this nanomodulated structure. This has further been corroborated by the observation of step hysteresis, magnetic force microscopy images of tunable magnetic dipoles, and quantitative micromagnetic simulations. An analytical expression has been derived to estimate the overall anisotropy accurately for nanomodulated film having low magnetocrystaline anisotropy. Derived mathematical expressions based on magnetic dipolar interaction are found to be in good agreement with our results.

'A piece of fine meshwork': the intertwining fiction of Philip Roth and Edna O'Brien

This thesis comprises a comparative analysis of the works the Irish author Edna O’Brien and her contemporary and friend, the Jewish-American author Philip Roth. It investigates the striking biographical, textual and stylistic symmetries between two writers from very different cultures and literary traditions. The thesis begins with the, until now, undetected intertextual nexuses between Roth’s fiction and O’Brien’s. These allusions significantly alter the readings of a number of their novels, while at the same time indicating wider transatlantic frames of reference now apparent in their work. O’Brien has, since the beginning of her career, been in frequent correspondence with all of the pre-eminent Jewish-American authors of her time, and her work conducts a dialogue with key Jewish-American texts. Conversely, Roth’s fiction—like O’Brien’s, obviously indebted to Joyce—has frequently alluded to other seminal Irish authors. The literary and personal relationship of Roth and O’Brien symbolize myriad links between Jewish and Irish literary cultures. In O’Brien’s (and wider Irish) fiction, the Jew is often positioned as an exotic but dangerous “Other”. Equally, throughout the Jewish canon Irish Catholics are frequently employed as foils. Roth and O’Brien investigate difference by depicting relationships that cross these boundaries. Through understanding the complex interrelations at play between the fiction of Roth and O’Brien, and between their work and that of a wider pantheon of Irish and American writers, this thesis will reposition both as transnational authors while developing a culturally sensitive, textually nuanced account of their transatlantic literary relations.