Instrumentation for Millimeter-wave Magnetoelectrodynamic Investigations of Low-Dimensional Conductors and Superconductors

We describe instrumentation for conducting high sensitivity millimeter-wave cavity perturbation measurements over a broad frequency range (40-200 GHz) and in the presence of strong magnetic fields (up to 33 tesla). A Millimeter-wave Vector Network Analyzer (MVNA) acts as a continuously tunable microwave source and phase sensitive detector (8-350 GHz), enabling simultaneous measurements of the complex cavity parameters (resonance frequency and Q-value) at a rapid repetition rate (approx. 10 kHz). We discuss the principal of operation of the MVNA and the construction of a probe for coupling the MVNA to various cylindrical resonator configurations which can easily be inserted into a high field magnet cryostat. We also present several experimental results which demonstrate the potential of the instrument for studies of low-dimensional conducting systems.Comment: 20 pages including fig

Detailed single crystal EPR lineshape measurements for the single molecule magnets Fe8Br and Mn12-ac

It is shown that our multi-high-frequency (40-200 GHz) resonant cavity technique yields distortion-free high field EPR spectra for single crystal samples of the uniaxial and biaxial spin S = 10 single molecule magnets (SMMs) [Mn12O12(CH3COO)16(H2O)4].2CH3COOH.4H2O and [Fe8O2(OH)12(tacn)6]Br8.9H2O. The observed lineshapes exhibit a pronounced dependence on temperature, magnetic field, and the spin quantum numbers (Ms values) associated with the levels involved in the transitions. Measurements at many frequencies allow us to separate various contributions to the EPR linewidths, including significant D-strain, g-strain and broadening due to the random dipolar fields of neighboring molecules. We also identify asymmetry in some of the EPR lineshapes for Fe8, and a previously unobserved fine structure to some of the EPR lines for both the Fe8 and Mn12 systems. These findings prove relevant to the mechanism of quantum tunneling of magnetization in these SMMs.Comment: Phys. Rev. B, accepted with minor revision

Place-Based Learning Communities on a Rural Campus: Turning Challenges into Assets

At Humboldt State University (HSU), location is everything. Students are as drawn to our spectacular natural setting as they are to the unique majors in the natural resource sciences that the university has to offer. However, the isolation that nurtures the pristine natural beauty of the area presents a difficult reality for students who are accustomed to more densely populated environments. With the large majority of our incoming students coming from distant cities, we set out to cultivate a “home away from home” by connecting first-year students majoring in science, technology, engineering and math (STEM) to the communities and local environment of Humboldt County. To achieve this, we designed first-year place-based learning communities (PBLCs) that integrate unique aspects and interdisciplinary themes of our location throughout multiple high impact practices, including a summer experience, blocked-enrolled courses, and a first-year experience course entitled Science 100: Becoming a STEM Professional in the 21st Century. Native American culture, traditional ways of knowing, and contemporary issues faced by tribal communities are central features of our place-based curriculum because HSU is located on the ancestral land of the Wiyot people and the university services nine federally recognized American Indian tribes. Our intention is that by providing a cross-cultural, validating environment, students will: feel and be better supported in their academic pursuits; cultivate values of personal, professional and social responsibility; and increase the likelihood that they will complete their HSU degree. As we complete the fourth year of implementation, we aim to harness our experience and reflection to improve our programming and enable promising early results to be sustained