3,877 research outputs found
Nanoindentation of bone: Comparison of specimens tested in liquid and embedded in polymethylmethacrylate
Elastic modulus of bone was investigated by nanoindentation using common methods of sample preparation, data collection, and analysis, and compared to dynamic mechanical analysis (DMA: three-point bending) for the same samples. Nanoindentation (Berkovich, 5 μm and 21 μm radii spherical indenters) and DMA were performed on eight wet and dehydrated (100% ethanol), machined equine cortical bone beams. Samples were embedded in polymethylmethacrylate (PMMA) and mechanical tests repeated. Indentation direction was transverse to the bone long axis while DMA tested longitudinally, giving approximately 12% greater modulus in DMA. For wet samples, nanoindentation with spherical indenters revealed a low modulus surface layer. Estimates of the volume of material contributing to elastic modulus measurement showed that the surface layer influences the measured modulus at low loads. Consistent results were obtained for embedded tissue regardless of indenter geometry, provided appropriate methods and analysis were used. Modulus increased for nanoindentation (21 μm radius indenter) from 11.7 GPa ± 1.7 to 15.0 GPa ± 2.2 to 19.4 GPa ± 2.1, for wet, dehydrated in ethanol, and embedded conditions, respectively. The large increases in elastic modulus caused by replacing water with ethanol and ethanol with PMMA demonstrate that the role of water in fine pore space and its interaction with collagen strongly influence the mechanical behavior of the tissue
Triple-Resonant Brillouin Light Scattering in Magneto-Optical Cavities.
An enhancement in Brillouin light scattering of optical photons with magnons is demonstrated in magneto-optical whispering gallery mode resonators tuned to a triple-resonance point. This occurs when both the input and output optical modes are resonant with those of the whispering gallery resonator, with a separation given by the ferromagnetic resonance frequency. The identification and excitation of specific optical modes allows us to gain a clear understanding of the mode-matching conditions. A selection rule due to wave vector matching leads to an intrinsic single-sideband excitation. Strong suppression of one sideband is essential for one-to-one frequency mapping in coherent optical-to-microwave conversion.Engineering and Physical Sciences Research Council (Grant ID: EP/ M50693X/1), European Research Council (Grant ID: 648613), Hitachi (Research Fellowship), Royal Society (University Research Fellowship), Winton Programme for the Physics of SustainabilityThis is the author accepted manuscript. The final version is available from the American Physical Society via https://doi.org/10.1103/PhysRevLett.117.13360
Identification of spin wave modes in yttrium iron garnet strongly coupled to a co-axial cavity
We demonstrate, at room temperature, the strong coupling of the fundamental and
non-uniform magnetostatic modes of an yttrium iron garnet (YIG) ferrimagnetic
sphere to the electromagnetic modes of a co-axial cavity. The well-de ned eld pro le
within the cavity yields a speci c coupling strength for each magnetostatic mode. We
experimentally measure the coupling strength for the di erent magnetostatic modes
and, by calculating the expected coupling strengths, are able to identify the modes
themselves.We would like to acknowledge support from Hitachi Cambridge Laboratory, and EPSRC Grant No. EP/K027018/1. A.J.F. is supported by a Hitachi Research fellowship.This is the author accepted manuscript. The final version is available from AIP at http://scitation.aip.org/content/aip/journal/jap/117/5/10.1063/1.4907694#fulltextAbstract
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Magneto-optical coupling in whispering-gallery-mode resonators
We demonstrate that yttrium iron garnet microspheres support optical
whispering gallery modes similar to those in non-magnetic dielectric materials.
The direction of the ferromagnetic moment tunes both the resonant frequency via
the Voigt effect as well as the degree of polarization rotation via the Faraday
effect. An understanding of the magneto-optical coupling in whispering gallery
modes, where the propagation direction rotates with respect to the
magnetization, is fundamental to the emerging field of cavity optomagnonics.Engineering and Physical Sciences Research Council (Grant IDs: EP/M50693X/1, EP/L027151/1), European Research Council (Grant ID: 648613), Hitachi (research fellowship), Royal Society (University Research Fellowship), Winton programme for the Physics of SustainabilityThis is the author accepted manuscript. The final version is available from the American Physical Society via http://dx.doi.org/10.1103/PhysRevA.92.06384
Cavity-mediated coherent coupling of magnetic moments
We demonstrate the long range strong coupling of magnetostatic modes in spatially separated ferromagnets mediated by a microwave frequency cavity. Two spheres of yttrium iron garnet are embedded in the cavity and their magnetostatic modes probed using a dispersive measurement technique. We find they are strongly coupled to each other even when detuned from the cavity modes, and investigate the dependence of the magnet-magnet coupling on the cavity detuning. Dark states of the coupled magnetostatic modes of the system are observed, and ascribed to mismatches between the symmetries of the modes and the drive field.We would like to acknowledge support from Hitachi Cambridge Laboratory, EPSRC Grant No. EP/K027018/1 and ERC Grant No. 648613. A.J.F. is supported by a Hitachi Research Fellowship. A.C.D. is supported by the ARC via the Centre of Excellence in Engineered Quantum Systems (EQuS), Project No. CE110001013.This is the author accepted manuscript. The final version is available from the American Physical Society via http://dx.doi.org/10.1103/PhysRevA.93.02180
The Influence of Natural Organic Matter on the Fate and Effects of Carbon Nanomaterials
2008 S.C. Water Resources Conference - Addressing Water Challenges Facing the State and Regio
Controlled enhancement of spin-current emission by three-magnon splitting
Spin currents—the flow of angular momentum without the simultaneous transfer of electrical charge—play an enabling role in the field of spintronics1, 2, 3, 4, 5, 6, 7, 8. Unlike the charge current, the spin current is not a conservative quantity within the conduction carrier system. This is due to the presence of the spin–orbit interaction that couples the spin of the carriers to angular momentum in the lattice. This spin–lattice coupling9 acts also as the source of damping in magnetic materials, where the precessing magnetic moment experiences a torque towards its equilibrium orientation; the excess angular momentum in the magnetic subsystem flows into the lattice. Here we show that this flow can be reversed by the three-magnon splitting process and experimentally achieve the enhancement of the spin current emitted by the interacting spin waves. This mechanism triggers angular momentum transfer from the lattice to the magnetic subsystem and modifies the spin-current emission. The finding illustrates the importance of magnon–magnon interactions for developing spin-current based electronics
Exchange magnon induced resistance asymmetry in permalloy spin-Hall oscillators
We investigate magnetization dynamics in a spin-Hall oscillator using a direct current measurement as well as conventional microwave spectrum analysis. When the current applies an anti-damping spin-transfer torque, we observe a change in resistance which we ascribe mainly to the excitation of incoherent exchange magnons. A simple model is developed based on the reduction of the effective saturation magnetization, quantitatively explaining the data. The observed phenomena highlight the importance of exchange magnons on the operation of spin-Hall oscillators
Experimental observation of the breaking and recombination of single Cooper pairs
We observe the real-time breaking of single Cooper pairs by monitoring the radio-frequency impedance of a superconducting double quantum dot. The Cooper pair breaking rate in the microscale islands of our device decreases as temperature is reduced, saturating at 2 kHz for temperatures beneath 100 mK. In addition, we measure in real-time the quasiparticle recombination into Cooper pairs. Analysis of the recombination rates shows that, in contrast to bulk lms, a multi-stage recombination pathway is followed.A.J.F. would like to acknowledge the Hitachi Research fellowship, support from Hitachi Cambridge Laboratory and support from the EPSRC grant EP/H016872/1. B.W.L. is supported by a Royal Society University Research Fellowship. F.A.P. would like to thank the Leverhulme Trust for fi nancial support.This is the author accepted manuscript. The final version is available from APS via http://dx.doi.org/10.1103/PhysRevB.90.14050
Complementary spin-Hall and inverse spin-galvanic effect torques in a ferromagnet/semiconductor bilayer.
This is the author accepted manuscript. The final version is available from NPG at http://www.nature.com/ncomms/2015/150331/ncomms7730/abs/ncomms7730.html.Recently discovered relativistic spin torques induced by a lateral current at a ferromagnet/paramagnet interface are a candidate spintronic technology for a new generation of electrically controlled magnetic memory devices. The focus of our work is to experimentally disentangle the perceived two model physical mechanisms of the relativistic spin torques, one driven by the spin-Hall effect and the other one by the inverse spin-galvanic effect. Here, we show a vector analysis of the torques in a prepared epitaxial transition-metal ferromagnet/semiconductor-paramagnet single-crystal structure by means of the all-electrical ferromagnetic resonance technique. By choice of our structure in which the semiconductor paramagnet has a Dresselhaus crystal inversion asymmetry, the system is favourable for separating the torques due to the inverse spin-galvanic effect and spin-Hall effect mechanisms into the field-like and antidamping-like components, respectively. Since they contribute to distinct symmetry torque components, the two microscopic mechanisms do not compete but complement each other in our system.The authors acknowledge support from EU European Research Council (ERC) advanced
grant no. 268066, from the Ministry of Education of the Czech Republic grant no.
LM2011026, from the Grant Agency of the Czech Republic grant no. 14-37427G and
the Academy of Sciences of the Czech Republic Praemium Academiae. A.J.F. acknowledges
support from a Hitachi research fellowship. H.K. acknowledges financial support from the
Japan Science and Technology Agency (JST)
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