Nanophotonic optomechanical devices allow observation of nanoscale vibrations with sensitivity that has dramatically advanced metrology of nanomechanical structures [1][2][3][4][5][6][7][8][9] and has the potential to impact studies of nanoscale physical systems in a similar manner [10,11]. Here we demonstrate this potential with a nanophotonic optomechanical torque magnetometer and radiofrequency (RF) magnetic susceptometer. Exquisite readout sensitivity provided by a nanocavity integrated within a torsional nanomechanical resonator enables observations of the unique net magnetization and RF-driven responses of single mesoscopic magnetic structures in ambient conditions. The magnetic moment resolution is sufficient for observation of Barkhausen steps in the magnetic hysteresis of a lithographically patterned permalloy island [12]. In addition, significantly enhanced RF susceptibility is found over narrow field ranges and attributed to thermally assisted driven hopping of a magnetic vortex core between neighboring pinning sites [13]. The on-chip magneto-susceptometer scheme offers a promising path to powerful integrated cavity optomechanical devices for quantitative characterization of magnetic micro-and nanosystems in science and technology.Torque magnetometry has seen recent resurgence owing to miniaturization of mechanical devices [14]. The high detection sensitivity of resonant nanomechanical torque sensors has allowed for minimally-invasive observations of magnetostatic interactions and hysteresis in a variety of magnetic materials including thin films [15], mesoscale confined geometries that are deposited [16] or epitaxially grown [17], and small aggregates of nanoparticles [18]. Going beyond the static limit, nanomechanical torque magnetometry has been extended to timescales allowing for detection of slow thermally-activated dynamics [12], AC susceptibility [17], and magnetic resonance [19,20].This powerful technique relies upon detection of the deflection of a mechanical element by angular momentum transfer originating from magnetic torques τ = µ 0 m×H, generated as the magnetic moments in the system, m, experience an orthogonally-directed component of the applied magnetic field, H. So far, improvements to torque magnetometers have been driven primarily by enhancements to the response of nanomechanical resonators resulting from their low mass and high mechanical quality factor (Q m ). Readout of magnetically driven motion has involved detection through free-space optical interferometric methods with very low optical quality factor (Q o ≈ 1) Fabry-Perot cavities formed between the nanomechanical resonator its supporting substrate [16]. However, as device dimensions scale down, and the number of magnetic spins become too small or the dynamics too fast, the mechanical deflections become more difficult to detect. Migration to a more sensitive readout scheme is essential. The integration of a nanoscale optical cavity offers a natural path for improvement. Nanocavity-optomechanical devices enhance mechanarXiv:...

23The measurements of magnetic hysteresis for aggregates of nanoparticles 24 deposited on a surface are reported. Magnetite nanoparticles derived from 25 magnetotactic bacteria are studied using nanomechanical torque magnetometry. 26The nanoparticles are deposited on high-stress Si3N4 membranes, to allow 27 inspection by electron microscopy, followed by focused ion-beam milling of 28 torsional resonators precisely located to capture selected aggregates within the 29 membrane area. Torque magnetometry is performed using the resonators. We 30 investigate also the magnetic torque-driven AC resonant modes of the modified 31 supporting membrane. The observations are compared to numerical simulations of 32 the mechanical modes, and to micromagnetic modeling of the hysteresis of a specific 33 measured cluster of ~ 350 nanoparticles.

No abstract

The thermal conductivity, thermal diffusivity and heat capacity per unit volume of dunite rocks taken from Chillas near Gilgit, Pakistan have been measured simultaneously using transient plane source technique. The temperature dependence of thermal transport properties is studied in the temperature range 83-303 K. Different relations for the estimation of thermal conductivity are also tested. Thermal conductivity data obey the modified Eucken’s law in the temperature range of measurements

No abstract

We report a highly compliant process for patterning nanoparticle arrays on micro- and nanomechanical devices. The distinctive step involves the single layer self-assembled nanoparticles on top of released nanomechanical devices. We demonstrate the process by fabricating sizable arrays of nanomechanical devices on silicon-on-insulator substrates, acting as nanomechanical torque magnetometers. Later, the nanoparticles were self-assembled in geometrical shapes on top of the devices by a unique combination of top-down and bottom-up methods. The self-assembled array of nanoparticles successfully showed a magnetic torque signal by magnetic actuation of the magnetometer. This patterning process can be generalized for any shape and for a wide range of nanoparticles on the nanomechanical resonators.

Mg-doped TlBa2(Ca2-xMgx)(Cu2.2Ti0.8)O10-δ (x = 0, 0.05, 0.15, 0.25, 0.35) superconductors Effect of paramagnetic Mn ion on the superconductivity of Cu0.5Tl0.5Ba2Ca2−xMnxCu3O10−y J. Appl. Phys. 112, 073920 (2012); 10.1063/1.4757405 Effect of Sn substitution on the para-conductivity of polycrystalline Cu 0.5 Tl 0.5 Ba 2 Ca 2 Cu 3 − y Sn y O 10 − δ superconductors

No abstract