Bulletin of the American Physical Society
Annual Meeting of the APS Four Corners Section
Volume 62, Number 17
Friday–Saturday, October 20–21, 2017; Fort Collins, CO
Session K6: Condensed Matter and Materials V |
Hide Abstracts |
Chair: Karine Chesnel, Brigham Young University Room: Lory Student Center 382 |
Saturday, October 21, 2017 9:25AM - 9:49AM |
K6.00001: Domain walls in magnetic nanowires Invited Speaker: Karen Livesey Magnetic domain walls are regions where the magnetization rotates from one direction to another inside a material. They are used in modern technologies to encode information, to perform logic operations, and even in lab-on-a-chip applications. In this talk I will discuss our recent analytic theories for predicting the shape of domain walls in very small rectangular nanowires, with cross-section on the order of 3x50 nm. These theories are shown to match very well with numerical calculations and with experimental results. The analytic theory therefore is an accurate tool for experimentalists in this field to use to predict domain wall shapes in various materials. Depending on the aspect ratio and material a nanowire is made from, either a so-called "Bloch" or "Neel" domain wall will form. The situation is even more complicated when interfacial Dzyaloshinkii-Moriya (asymmetric exchange) interaction occurs in a material. A rich phase diagram of domain wall types will be presented. [Preview Abstract] |
Saturday, October 21, 2017 9:49AM - 10:01AM |
K6.00002: High-Bandwidth Scanning Hall Probe Microscopy of Superconducting Flux Vortices A. D. DeMann, S. B. Field Type-II superconductors experience a mixed state in which lines of quantized magnetic flux penetrate the bulk of the superconducting material. These \textit{vortices} interact with one another, electrical currents, and local material parameters. Traditional low-bandwidth ($\sim$100$\,$Hz) scanning Hall probe microscopy (SHPM) has often been employed to image the static configurations caused by these interactions. However, the limited bandwidth and slow scan times of traditional SHPM do not allow dynamical states of moving vortices to be imaged; such studies require signal bandwidths in the MHz range. By developing specialized Hall sensors and a cryogenic JFET preamplifier, we have extended the operating bandwidth of our SHPM to $\sim$10$\,$MHz. [Preview Abstract] |
Saturday, October 21, 2017 10:01AM - 10:13AM |
K6.00003: Maximizing the Magnetic Domain Morphologies in CoPt thin-films Carson Richards, Karine Chesnel I am doing research under Dr. Chesnel at Brigham Young University in Provo, Utah. The research involves studying the magnetic domain morphologies of CoPt thin-films ranging from 55-335 nanometers in thickness. In these CoPt~multilayer thin-films, the thickness of the individual Co layers varies in the samples from~0.4 to 6~nanometers and the thickness of the individual~Pt layer is 0.7 nanometers, these two layers repeat 50 times. My sample is 75 nm in total comprised of 0.8 nm thick layers of cobalt and 0.7 nm thick layers of platinum. I~will present~results for~a Co thickness of 8 Angstroms.~ We used a Vibrating Sample Magnetometer (VSM)~to apply a strong magnetic field looping sequence to the sample before returning to net-zero magnetization. We then used an Atomic Force Microscope (AFM) to map the magnetic domains. We repeated this process, of~alternatively using the VSM and AFM, until we completed an ascending series from 0 Tesla to 9 Tesla. The densities of the magnetic domains of the individually and previously applied loops in each state were then analyzed. I am looking for the relationship between the magnitude of the previously applied magnetic field and the density of the magnetic domains in three different types of series.~These are ascending vs descending vs pumping. [Preview Abstract] |
Saturday, October 21, 2017 10:13AM - 10:25AM |
K6.00004: Spin-wave fractals in a quasi-one-dimensional magnonic crystal Daniel Richardson, Boris Kalinikos, Lincoln Carr, Mingzhong Wu Fractals are a ubiquitous phenomenon in nonlinear physics and a key facet of natural systems, from the lungs in our bodies to attractors underlying the weather. Spin-wave fractals have previously been observed in a Y$_{\mathrm{3}}$Fe$_{\mathrm{5}}$O$_{\mathrm{12}}$ (YIG) thin film-based active feedback ring, where the periodic amplification ensures the strong nonlinearity of the spin waves, while the periodic feedback was used as a time-dependent potential to create regions of large dispersion in the spin-wave spectrum. Strong nonlinearity and high dispersion are two essential ingredients needed for fractal development. This presentation reports for the first time that it is also possible to use a position-dependent potential to create the large dispersion necessary for fractal formation. As the power ($P_{\mathrm{in}})$ delivered to the magnonic crystal increases, one observes that a frequency comb forms around the input microwave frequency ($f_{\mathrm{0}})$, where the strongest peak sits at $f_{\mathrm{0}}$. As $P_{\mathrm{in}}$ is increased further, each peak in the comb evolves into its own, finer frequency comb. If $P_{\mathrm{in}}$ is increased even further, one can observe yet another set of finer frequency combs. [Preview Abstract] |
Saturday, October 21, 2017 10:25AM - 10:37AM |
K6.00005: Optical investigations of the photo-spin-voltaic effect in metal/magnetic insulator heterostructures Subash Kattel, Joseph R. Murphy, David Ellsworth, Peng Li, Mingzhong Wu, William D. Rice Pure spin currents in metals can be produced via injection from thermal gradients applied across magnetic insulators (spin Seebeck effect) or by utilizing microwave-driven spin precession in an adjacent ferromagnet (spin pumping). Recently, pure spin currents were directly created in a normal metal by optically exciting nanometer-thick Pt on Y$_3$Fe$_5$O$_{12}$ (YIG). Our initial measurements of the photo-spin-voltaic (PSV) effect with a broadband light source suggested that photogenerated carriers in the Pt produced a spin voltage when excited with near-infrared light. Here, we use narrowband excitation to show that the PSV signal can be generated across a broad optical range; we observe that the PSV effect is nearly constant from 350 to 1600 nm. Despite strong spin-orbit coupling in Pt, we show that the PSV effect is insensitive to the light polarization and only depends on the optical power. To distinguish the PSV effect from light-induced heating, we performed time- and field-dependent measurements and saw significant differences in the respective behaviors. Although continued work is necessary, our measurements suggest that pure spin currents can be optically generated in Pt/YIG hetereostructures over spectral ranges that span the Si/InGaAs detection gap. [Preview Abstract] |
Saturday, October 21, 2017 10:37AM - 10:49AM |
K6.00006: Temperature Dependence in the Magnetic Properties of FeRh/Ni Bilayers Joshua Lauzier, Logan Sutton, Jose de la Venta The temperature dependence of the coercivity and magnetization of FeRh/Ni bilayers was studied. FeRh exhibits a Magnetostructural Phase Transition at critical temperature T$_{\mathrm{C}}$ \textasciitilde 370 K, from a low temperature antiferromagnetic (AFM) to a high temperature ferromagnetic (FM) state. The magnetic transition of FeRh influences the coercivity and magnetization of the Ni films. In addition, the growth conditions allow tuning of the magnetic properties of the bilayer below T$_{\mathrm{C}}$. When Ni films are grown on top of FM FeRh, the two layers are exchange coupled at temperatures below T$_{\mathrm{C}}$. On the other hand, when the Ni films are deposited on AFM FeRh, the two layers act like two independent ferromagnetic layers without coupling below T$_{\mathrm{C}}$. These results indicate that properties of FeRh/Ni bilayers are strongly affected by the growth conditions and that it is possible to control their magnetic properties by tuning the growth conditions. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700