The influence of external magnetic fields on the bending vibration of a one-side clamped iron filled carbon nanotube (CNT) has been analyzed theoretically and experimentally, with particular consideration given to the changes in the resonance frequency. The model involves the application of a modified Euler-Bernoulli-beam to analyze the zero field oscillatory behavior, as well as a magnetostatic approach used to determine the influence of any external field distributions. The experiments were conducted in situ in a scanning electron microscope. The measured magnetic moment of the nanowire at room temperature was μ = 2.1 × 10−14 Am2. Due to the favorable geometry of the CNT oscillator, the raw signal obtained using this approach is significantly more favorable than that with state of the art cantilever magnetometry. The obtained good agreement between model and experiment provides a valuable basis for the development of nanoelectromechanical systems in which magnetic interactions are relevant.
We present a bimodal magnetic force microscopy sensor consisting of a conventional cantilever beam, a spacer element, and an iron-filled carbon nanotube. Depending on the mode of the cantilever's resonant flexural vibration, the sensor is sensitive to magnetic field derivatives parallel and perpendicular to the sample's surface. This multifunctionality is supported by the scalar-type behavior of the magnetic monopole-like end of the iron-filled carbon nanotube.
This paper reports grain-size-dependent magnetic susceptibility data on nanocrystalline bulk Tb. We find that at small grain size Curie–Weiss behavior is not present for temperatures up to about 80K above the transition temperature and that the helical antiferromagnetic phase is absent. Possible origins for the suppression of the helix phase in nanoscaled Tb are discussed in terms of internal magnetostatic fields and competing length scales (grain size versus wavelength of the helix phase).
We report on the results of grain-size and temperature-dependent magnetization, specific-heat, and neutron-scattering experiments on the heavy rare-earth metals terbium and holmium, with particular emphasis on the temperature regions where the helical antiferromagnetic phases exist. In contrast to Ho, we find that the helical structure in Tb is relative strongly affected by microstructural disorder, specifically, it can no longer be detected for the smallest studied grain size of D = 18 nm. Moreover, in coarse-grained Tb a helical structure persists even in the ferromagnetic regime, down to about T = 215 K, in agreement with angle-resolved photoelectron spectroscopy (ARPES) data, which reveal a nesting feature of the bulk Fermi surface at the L point of the Brillouin zone at T = 210 K. As samples for the ARPES measurements, we used 10-nm-thick single-crystalline Tb films that show a bulk electronic valance-band structure. Thus, our ARPES measurements are used to discuss temperature-induced effects observed in the coarse-grained samples.
An iron filled carbon nanotube (FeCNT), a 10-40 nm ferromagnetic nanowire enclosed in a protective carbon tube, is an attractive candidate for a magnetic force microscopy (MFM) probe as it provides a mechanically and chemically robust, nanoscale probe. We demonstrate the probe's capabilities with images of the magnetic field gradients close to the surface of a Py dot in both the multi-domain and vortex states. We show the FeCNT probe is accurately described by a single magnetic monopole located at its tip. Its effective magnetic charge is determined by the diameter of the iron wire and its saturation magnetization 4πM(s) ≈ 2.2 × 10(4)G. A magnetic monopole probe is advantageous as it enables quantitative measurements of the magnetic field gradient close to the sample surface. The lateral resolution is defined by the diameter of the iron wire and the probe-sample separation.
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