Novel Faraday Rotation Effects Observed In Ultra-Thin Iron Garnet Films

Recent work performed by A. Chakravarty and M. Levy showed experimentally a dramatic increase in the specific Faraday Rotation (FR) of the iron garnet Bi0.8Lu0.2Gd2Fe5O12. A theoretical model, based purely on classical electrodynamics, attempting to explain this behavior was developed by colleagues in Russia that not only confirmed the asymptotic increase in the specific FR at sub-50nm film thicknesses but also suggested that the specific FR should exhibit significant fluctuations at sub-500 nm film thicknesses. The original data points were widespread with steps of 50 nm or more between data points that skipped over the theoretical oscillations. Presented herein are the results of performing high-resolution data point steps of 5-15 nm with the intent of catching the oscillations. We have obtained data that confirms the presence of significant oscillations at thicknesses below 100 nm and have reconfirmed the behavior previously shown at ultrathin thicknesses. While the proposed model confirms some of the basic features of the original experimental data and makes additional predictions, now confirmed through the work reported in this thesis, further analysis is still needed to fully explain the observed experimental results. We have also included some possible explanations for this phenomenon

YOU [DON’T] GOTTA PAY THE TROLL TOLL: A TRANSACTION COSTS MODEL OF ONLINE HARASSMENT

This year’s conference theme challenges us to imagine. When it comes to the future of the internet, is it possible to imagine a space where users are free from harassment? Probably not. But it is possible to imagine spaces where the effort to harass outweighs the efforts from victims to stop the harassment. How might we begin to create this future? I propose that it starts with a reframing of the language currently used to describe these issues. In this paper I will lay out a conceptual framework for describing the processes users—both the harassed and the harassers—must go through to participate in an online environment. Given that harassment occurs across platforms, it is important that we have a way of speaking about these processes that encompasses all the potential spaces where harassment happens. Drawing from economics, I present a Transaction Cost model to describe, predict, and hopefully offer solutions to reduce online harassment

The Privacy of Others

Much of the previous work on privacy has centered on the discloser-based behaviors of users and corresponding relational implications of privacy. This dissertation flips the view of privacy and explores information acquisition privacy norms. That is, it looks at how we behave towards the privacy of others. Taking the Ashley Madison hack as a case study, the research questions sought to identify the frames used in Twitter discourse and media coverage of the hack. Communication, Privacy Theory, and Frame Theory inform this study. Using Latent Dirichlet Allocation (LDA), the research identified six primary themes in the twitter discussion: Breaking News, Outing, Public Sector Fallout, Legal Fallout, Business Fallout, and Personal Fallout. The LDA then guided the qualitative Critical Discourse Analysis that was conducted to identify prominent frames. Two over-arching frames emerged that shaped decisions and attitudes towards using or accessing stolen data from the hack: The Privacy of Others is Expendable (POE) and The Privacy of Others is the Privacy of Us All (POA). In Twitter discourse the POE frame was enabled by the following mechanisms: Schadenfreude, Privacy as Earned, and Privacy is Dead. The POA frame utilized the mechanisms Privacy is a Right and It Could Happen to You. In media coverage, the POE frame relied on the following mechanisms: Obfuscation, Flattening of “Publicness,” Mimicry, and Inevitability. Conversely, media coverage that included the POA frame used: Privacy as Security, and Rejection of Puritanical Glee. This research uncovered the following three critical points. First, the current privacy theory inadequately addresses a new type of privacy violation: Mass Impersonal Social Monitoring (MISM). MISM occurs when a large amount of information about a large number of people is made available (typically through illegal means) online, and a large number of people engage in searching through that information. Searching behavior is not necessarily driven by relational reasons, but consequences for hacked individuals are social in nature. Second, media are obscuring the debate around the privacy rights of individuals caught in large-scale hacks. And finally, the media may have a friend in bots in that bots actively amplify media messages by re-distributing media frames

Predicting Opinion Leaders in Twitter Activism Networks The Case of the Wisconsin Recall Election

This study employs content and network analysis techniques to explore the predictors of opinion leadership in a political activism network on Twitter. The results demonstrate the feasibility of using user-generated content to measure user characteristics. The characteristics were analyzed to predict users’ performance in the network. According to the results, Twitter users with higher connectivity and issue involvement are better at influencing information flow on Twitter. User connectivity was measured by betweenness centrality, and issue involvement was measured by a user’s geographic proximity to a given event and the contribution of engaging tweets. In addition, the results show that tweets by organizations had greater influence than those by individual users

The Rules of Engagement: Managing Boundaries, Managing Identities

This panel takes the conference theme "Internet Rules" to heart by delving into the rules that govern information disclosure and acquisition. All of the papers are grounded in privacy theory--ranging from networked privacy to boundary work--but each offers a unique perspective on areas of internet research such as identity management, privacy, and politics. Taken together, these papers present an overview of the various rules of online engagement."Other People's Privacy: A Case Study of the Ashley Madison Data Breach" asks what privacy rules look like when considered from the aspect of information acquisition. It argues that the act of acquiring information--especially when that information is available because of a known privacy violation--reveals as much about privacy values as does the act of disclosing in the first place. It asks "Do the rules change when they pertain to other people's information?" Using Twitter data, it presents results from a conversation and discourse analysis of Ashley Madison tweets to reveal a hierarchy of social norms, one in which privacy values operate as a function of other social norms.The rules of interaction between teachers and students have seen a number of changes as a result of social networking technologies that are introduced to the learning environment. "Teachers’ Experiences of Boundary Turbulence: The Case of Wilma in Finnish High Schools" investigates boundary management conducted by teachers learning to adjust to a new method of engagement with students. It asks (1) how teachers regulate interpersonal boundaries in the presence of this system and (2) how they cope with challenges that the introduction of such a system causes. This case study sheds lights on the creation of new boundaries by teachers used to manage professional and personal life.For many, the idea of talking about politics on Facebook is akin to talking about religion at a bar: It's simply against the rules. "Political, Public, and Proud! What We Can Learn From the Minority of Citizens Who Experiment With Political Communication on Facebook" presents a study of individuals who ignore this unwritten rule and use Facebook as a space to discuss political topics. Using in-depth and longitudinal observation of Facebook profiles, focus groups and individual interviews with ten Danish citizens who used Facebook for sharing political opinions it develops a model that explains the process of status updates as the transition from private thinking, to public thinking, and finally public communication."Profile Work for Preserving Privacy on Social Network Sites" offers an explanation of the links between privacy and identity. Playing on the rules of authenticity, it fleshes out how the changed dynamics of self-presentation create a threat towards one's networked privacy. Drawing on three key differences between offline and online identity management (role dynamic, temporality, and communication realm) it argues that prolonged identity performance, as required by SNS such as Facebook, presents challenges to networked privacy by requiring extensive profile work from its users. It argues in favor of a recent turn in SNS profile features, one that shortens identity performances decreases the need for profile work, helping users to maintain their authenticities within their social realms

Who’s Running the Show? Negotiating Control for Community Participation

As the internet and communication technologies have come to dominate daily life practices, the nuance in the complex relationships between social practices and the technologies that mediate them are sometimes obscured by the ability to aggregate. With the goal of getting at the heart of the nuance that shapes cultural participation, this paper session highlights the qualitative analysis of communities that emerge through the affordances of communication technologies. Ranging from political communities in China to cultural communities of fandom, each of these papers asks how everyday users employ tactics of resistance and/or appropriation to negotiate a digital space for their collective voices. Perhaps the most illustrative example of Twitter as a site of resistance was the Arab Spring. But in addition to its ability to mobilize political actors, Twitter affords opportunities for more subtle cultural power struggles. When the lights went out in the Superdome for Super Bowl XLVII, for example, Twitter erupted. During the blackout, users generated a staggering 285,000 tweets per minute—more than at any other point during the game. An analysis of tweets containing the #Lightsout hashtag revealed an interested trend: pop culture references. Interestingly, these tweets renegotiated the Super Bowl narrative as a form of storytelling—specific to their referenced pop culture text—under the shared theme of a hashtag. #Lightsout allowed potentially marginalized “Geek culture” communities to appropriate the Super Bowl narrative away from the classic machismo, consumerist rhetoric to one of their own. In China, as the tightening of state control over the mass media persists, people are left with only limited or no access to mass media and a mass-mediated public sphere. Yet China has both the world’s most active social network population and the world’s largest online population. How—and to what extent—are everyday use of new media articulating Chinese people’s experiences and shaping their social memory? An analysis of Weibo (China’s equivalent of Twitter) tweets from cities that were sites of collective action shows that Chinese social media provide people an alternative communicative sphere for sharing and accumulating “unofficial” social memory as a kind of covert resistance. While the #Lightsout and Weibo examples both highlight the potentially empowering effects of media technologies, the labor of contribution is not without its costs. On television websites and blogs, fans actively engage in the act of recapping—crafting a summary of a television show episode. Once a playful expression of fandom, the pressure to produce fresh, witty content in a timely manner challenges the play aspect of the activity. An analysis discusses the ways in which the recap can serve as an example of the tension inherent to convergence culture, where emphasis on the production and circulation of media content depends heavily on the participation of the consumer. As fans have reached out to media producers through the likes of recaps and roleplayers, to name a few methods, many media outlets are now actively reaching back to their fans through show and character specific Twitter accounts. This work studies the tweets from five television show accounts (The Americans, Breaking Bad, FaceOff, Grimm, and House of Cards) to characterize the way they interact with their fans and promote their shows. Findings indicate these shows use a variety of practices to encourage fan anticipation of new episodes and seasons, as well as participation in the story or fan group. Anticipation is supported through content sharing, countdowns, and discussions of watching styles, while participation focused practices include interaction with fans and performers/producers, use of insider knowledge and humor, and explicit calls for participation. Drawings from a wide range of topics, these papers highlight how resistance, and/or appropriation of narratives or technologies contribute to the complexity of social practices

Faraday rotation in iron garnet films beyond elemental substitutions

In previous decades, significant efforts have been devoted to increasing the magneto-optical efficiency of iron garnet materials for the miniaturization of nonreciprocal devices such as isolators and circulators. Elemental substitutions, or proper nanostructuring to benefit from optical resonances, have been pursued. However, all these approaches still require film thicknesses of at least several tens of microns to deliver useful device applications, and suffer from narrow bandwidths in the case of optical resonance effects. This paper reports on a newly discovered enhancement of the Faraday effect observed experimentally in nanoscale bismuth-substituted iron garnet films. It is shown here that this enhancement is not due to elemental substitution or compositional variations, nor is it due to photon trapping or resonance effects. Comprehensive experimental and theoretical analysis of the Faraday rotation reveals a dramatic sevenfold amplification in the magneto-optic gyrotropy within only 2 nm of the air–surface interface, corresponding to just a couple of atomic monolayers as a result of symmetry breaking at the air–film interface. This finding opens up an avenue to the application of monolayer magnetic garnets for the control of light

Influence of Pressure on the Magnetic Response of the Low-Dimensional Quantum Magnet Cu(H₂O)₂(C₂H₈N₂)SO₄

The influence of pressure on the low-dimensional molecular magnet Cu(H₂O)₂(en)SO₄ (en = ethylenediamine = C₂H₈N₂) has theoretically been shown to affect the exchange interactions of the material. Herein, the results of an experimental study of hydrostatic pressure effects on the temperature dependence of the magnetization are reported. Using two different pressure cells, the magnetization measurements were performed between 2 K and 9.6 K with pressures ranging from ambient to 5.0 GPa. The data preliminarily suggest the presence of a shift in the magnetization peak of the material at the lowest temperatures and at the highest applied pressures. These data serve as a guide for future experimental work employing pressure to study this intriguing system