Bulletin of the American Physical Society
2015 Annual Spring Meeting of the APS Ohio-Region Section
Volume 60, Number 3
Friday–Saturday, March 27–28, 2015; Kent, Ohio
Session F5: Condensed Matter III |
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Chair: Maxim Dzero, Kent State University Room: KSU Student Center 317 |
Saturday, March 28, 2015 11:35AM - 11:50AM |
F5.00001: Absolute measurements of radio-frequency magnetic susceptibility Matthew Vannette Radio frequency ($f\approx 1-20$ MHz) magnetic susceptibility ($\chi=dM/dH$) measurements show considerable utility in the study of many condensed matter systems. The principle of operation is straightforward and requires little specialized equipment. However, the obtained data (frequency shift, $df$, of an $LC$ oscillator) suffer from important drawbacks. In metallic samples the data are a convolution of intrinsic magnetic effects and electromagnetic screening due to the normal state skin effect. The convolution can make interpretation of results subtle. More significant, perhaps, is that the data are only semi-quantitative at best. The coefficient that converts $df$ to $\chi$ depends on geometric quantities that are either not well known or difficult to determine or both. A method for determining this coefficient by direct measurements of $df$ is presented. This allows for fully quantitative measurements of $\chi$ at radio frequencies thereby permitting comparisons across materials and frequencies. [Preview Abstract] |
Saturday, March 28, 2015 11:50AM - 12:05PM |
F5.00002: Electroabsorption spectroscopy of bulk heterojunction solar cells Marian Tzolov Bulk heterojunction solar cells were fabricated using PCPDTBT polymer and PCBM in inert atmosphere. Electroabsorption (EA) spectroscopy was performed in the spectral range 350-1000 nm using detection at the first harmonic of the modulation frequency. The first derivative of the optical absorbance spectra explains satisfactory most of the bands in the EA spectra. The only deviation is in the spectral range around 760 nm. Control experiments with device structures containing only a PCPDTBT film confirm that the band at 760 nm is associated with the presence of PCBM, despite that pristine PCBM is not expected to have such spectral band. We show that electrical DC bias strongly affects this band. Negative DC bias almost completely eliminates this band, while positive bias enhances it further. We interpret the band at 760 nm as due to photogenerated charge carriers trapped at defect states or at interfaces within the composite PCPDTBT/PCBM film. Our interpretation is supported further by the current voltage characteristics, impedance spectra, photocurrent spectra, frequency dependence and DC bias dependence of the EA signal. The effective transfer of photogenerated charge carriers between PCPDTBT and PCBM is confirmed by the quenching of the photoluminescence in the composite film. [Preview Abstract] |
Saturday, March 28, 2015 12:05PM - 12:20PM |
F5.00003: First Experimental Demonstration of Coherent Perfect Rotation Michael Crescimanno, Chuanhong Zhou, James Andrews We present experimental results from a recent laboratory demonstration of coherent perfect polarization rotation (CPR) which is a conservative, reversible counterpart to coherent perfect absorption (a.k.a. the anti-laser). We conclude with a brief summary of new experiments underway that will be critical to applications of CPR in various non-reciprocal optical technologies. [Preview Abstract] |
Saturday, March 28, 2015 12:20PM - 12:35PM |
F5.00004: X-Ray Photoemission Spectroscopy Study of 4140 Steel Surfaces Treated With 3-Aminopropyltriethoxysilane Courtney Richards, Stephen Cornich, Holly Martin, Snjezana Balaz In this study, we used X-ray Photoemission Spectroscopy (XPS) to investigate elemental, chemical state, and electronic properties of 4140 steel surfaces. To better understand the effects of various activation methods on the types of oxides present, the steel surfaces underwent three different treatments, specifically piranha [1], H2SO4, and HCl. The ability of the oxides to bond with 3-Aminopropyltriethoxysilane (APTES) was also investigated. The treated 4140 steel surfaces were compared with and without APTES, examining changes in the types of oxygen, carbon, nitrogen, and silicon present. The purpose of this study was to investigate the surface reactions and to gain a better understanding of the surface chemistry of treated 4140 steel. The findings of the relationships between the different activation methods and their ability to bond APTES to the surface will lead to the development of a reaction scheme to bond chitosan, a bactericidal polymer, to steel for the prevention of microbially-influenced corrosion on oil pipelines. \\[4pt] [1] Martin, H.J.; Schulz, K.H.; Bumgardner, J.D.; Walters, K.B. Langmuir 2007, 23, 6645-6651. [Preview Abstract] |
Saturday, March 28, 2015 12:35PM - 12:50PM |
F5.00005: Magnetic and structural properties of Ni$_{2}$Mn$_{1-x}$Cr$_{x}$In Jeffrey Brock, Mahmud Khan The discovery of the martensitic phase transition (MPT) in a ferromagnetic (FM) state in Ni$_{2}$MnGa by Webster [P. J. Webster, K. R. A. Ziebeck, S. L. Town, and M. S. Peak, Philos. Mag. B \textbf{49}, 295 (1984)] in the early 80's have generated an intense research interest in Ni$_{2}$MnX (X $=$ Ga, In, Sb, Sn) based stoichiometric and off-stoichiometric Heusler alloys. The continuous research efforts on these alloys have resulted in the discoveries of several fascinating properties including magnetocaloric effects (MCE) [Albertini et al., J. Magn. Mater. \textbf{272-276}, 2111 (2004)], large magnetoresistance (MR) [K. Koyama et al., Appl. Phys. Lett. \textbf{89}, 182510 (2006)] and exchange bias effects [Khan et al,, Appl. Phys. Lett. \textbf{9}1, 072510~(2007)],[ Li et al,, Appl. Phys. Lett. \textbf{91}, 112505 (2007)]. The multifunctional properties of these Heusler alloys can be controlled by manipulating the Mn concentration. Keeping this in mind, we have performed an experimental study on the structural and magnetic properties of Cr doped Ni$_{2}$Mn$_{1-x}$Cr$_{x}$In Heusler alloys. The goal is to investigate and understand the effect of Cr doping on the magnetic and structural properties of these alloys. X-ray diffraction measurements reveal that the alloys exhibit the L$_{21}$ cubic structure at room temperature. Magnetization and ac susceptibility measurements have been conducted to explore the magnetic properties of the samples. For all Cr concentrations, the alloys are ferromagnetic. The saturation magnetization and Curie temperature decreases with increasing Cr concentration. The ac susceptibility data show additional anomalies that change with change in Cr concentration. [Preview Abstract] |
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