Magnetic damping impacts essential dynamics for spintronic device applications, but its fundamental mechanisms in various materials – including simple ferromagnetic metals – have yet to be understood. Here, we experimentally correlate damping with structural and transport properties of epitaxial thin films of Fe. At room temperature, the effective Gilbert damping parameter is independent of whether these films are coherently strained or partially relaxed. However, at low temperature, we find that coherently strained Fe films with higher crystalline quality and conductivity exhibit higher damping. The enhancement of low-temperature damping is greater than that from classical eddy current loss. Our observation of such conductivity-like damping, possibly governed by the intraband scattering mechanism [1], provides fundamental insight into the role of crystallinity in damping in ferromagnetic metals.
[1] K. Gilmore, Y. U. Idzerda, M. D. Stiles, Phys. Rev. Lett. 99, 027204 (2007); M. A. W. Schoen et al. Nat. Phys. 12, 839 (2016).
TRS is developing new actuators based on single crystal piezoelectric materials such as Pb(Zn1/3Nb2/3)1-xTixO3 (PZN-PT) and Pb(Mg1/3Nb2/3)x-1TixO3 (PMN-PT) which exhibit very high piezoelectric coefficients (d33 = 1800-2200 pC/N) and electromechanical coupling factors (k33 > 0.9), respectively, for a variety of applications, including active vibration damping, active flow control, high precision positioning, ultrasonic motors, deformable mirrors, and adaptive optics. The d32 cut crystal plate actuators showed d32 ~ -1600 pC/N, inter-digital electroded (IDE) plate actuators showed effective d33 ~ 1100 pC/N. Single crystal stack actuators with stroke of 10 μm-100 μm were developed and tested at both room temperature and cryogenic temperatures. Flextensional single crystal piezoelectric actuators with either stack driver or plate driver were developed with stroke 70 μm - > 250 μm. For large stroke cryogenic actuation (> 1mm), a single crystal piezomotor was developed and tested at temperature of 77 K-300K and stroke of > 10mm and step resolution of 20 nm were achieved. In order to demonstrate the significance of developed single crystal actuators, modeling on single crystal piezoelectric deformable mirrors and helicopter flap control using single crystal actuators were conducted and the modeling results show that more than 20 wavelength wavefront error could be corrected by using the single crystal deformable mirrors and +/- 5.8 ° flap deflection will be obtained for a 36" flap using single crystal stack actuators.
Diffraction investigations have been performed ojn poled 0.75Pb(Mg1/3Nb2/3)O3-0.25PbTiO3 crystals of cubic shape, where each cube face was oriented along a (001)-type plane. Contour small area reciprocal space scans of the three (001) faces of the cube were found to be in-equivalent. The results demonstrate a high micro-domain density within the poled condition, where micro-domain averagign produces monoclinic symmetry.
Piezoelectric single crystals of lead magnesium niobate in solid solution with lead titanate have generated great interest in the Navy sonar community because of the potential they offer for enhanced transducer performance. Two material properties, in particular, make the piezoelectric single crystals unique; their high 33-mode coupling factor and their low short circuit Young's modulus. Measurements of the large signal electromechanical and mechanical properties on single crystal samples are presented in this paper. These measurements elucidate the behavior of piezoelectric single crystals, including the effect of bias field on the Young's modulus. The ramifications of the measured material properties on transducer design are also discussed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.