| Thursday, April 13, 2017 |
| Various grad students, NYU | |
| Event Type: HEP Journal Club | |
| Time: 1:00 PM - 2:00 PM | |
| Location: 726 Broadway, 902, Lg Conf | |
| Nanomagnetic Playground: Magneto-Ionics and HAMR Media | |
| Kai Liu, UC Davis | |
| Event Type: CQP Seminar | |
| Time: 2:00 PM - 3:00 PM | |
| Location: Meyer 5th Fl. CCPP Lounge | |
| Abstract: The coming end of Moore’s law underscores the urgency of developing highly energy-efficient nanoelectronics. Spintronics offers an exciting new paradigm to address this grand challenge. In this talk I will first discuss magneto-ionic control of metal/oxide heterostructures, which offers a highly effective means to tailor material properties via modification of the interfacial characteristics. Currently, direct observation of ionic motion under buried interfaces and demonstration of its correlation with the physical properties have been challenging. Utilizing the strong oxygen affinity of gadolinium, we design a model system of GdFe/NiCoO bilayer films, where the oxygen migration is observed and manifested in a controlled positive exchange bias [1]. We further show that the magnetoelectric coupling moderated by voltage-driven oxygen migration extends beyond the interface region in relatively thick AlO x /GdO x /Co(15 nm) films [2]. In the second part I will discuss a magnetometry-based order parameter to characterize high anisotropy L1 0 FePt films that are prototype media for the emerging heat-assisted magnetic recording (HAMR) technology. We also show an extremely sensitive magnetic yoking effect and tunable interactions in FePt based hard/soft bilayers mediated by the soft layer [3]. These findings demonstrate an effective approach to design and control magnetic interactions in wide varieties of magnetic nanostructures and devices. | |
| Blanton, Tinker, Pullen | |
| Event Type: Group Meeting | |
| Time: 2:00 PM - 3:30 PM | |
| Location: 726 Broadway, 901, Sm Conf | |
| Highly magnetic neutron stars: bewildering astrophysical laboratories and cosmological tools | |
| Rosalba Perna, Stonybrook | |
| Event Type: Physics Dept Colloquium | |
| Time: 4:00 PM - 5:00 PM | |
| Location: Meyer 122 | |
| Abstract: The death of massive stars leaves behind exotic compact objects, that is neutron stars and black holes. Among the neutron stars, especially interesting are the Anomalous X-ray Pulsars and Soft Gamma-Ray Repeaters (SGRs), which are young neutron stars characterized by high X-ray quiescent luminosities, outbursts, and, in the case of SGRs, sporadic giant flares. They are believed to be magnetars, that is neutron stars powered by ultra-strong magnetic fields. However, the diversity of their behaviours, and, especially, the observation of magnetar-like bursts from 'low-field' neutron stars, has been a theoretical puzzle. In the first part of the talk, I will discuss results of long-term MHD simulations which, by following the evolution of magnetic stresses within the neutron star crust, have allowed to relate the observed magnetar phenomenology to the physical properties of the neutron stars, and in particular to their age and magnetic field strength and topology. The dichotomy of 'high-B' field pulsars versus magnetars is naturally explained, and occasional outbursts from old, low B-field neutron stars are predicted. In the second part of the talk, I will discuss how observations of highly magnetized neutron stars can be handy tools in the cosmological domain, and in particular as a way to set constraints on the hypothetical particle 'axion'. | |