ABSTRACT
A large enhancement of the magnetic anisotropy of Ni nanowires (NWs) embedded in anodic aluminium oxide porous membranes is obtained as a result of an induced magnetoelastic (ME) anisotropy contribution. This unusual large anisotropy enhancement depends on the diameter of the NWs and exceeds the magnetostatic (MS) contribution. As a consequence, it leads to effective magnetic anisotropy energies as large as 1.4 × 10(6) erg cm(-3), which are of the same order of magnitude and comparable to the MS energies of harder magnetic materials like Co NWs. Specifically, from ferromagnetic resonance experiments, the magnetic anisotropy of the NWs has been observed to increase as its diameter is decreased, leading to values that are about four times larger than the corresponding value when only the MS anisotropy is present. Our results are consistent with the recently proposed growth mechanism of Ni NWs that proceeds via a poly-crystalline stage at the bottom followed by a single-crystalline stage with texture [110] parallel to the axis of the NWs. A strong correlation between reducing the diameter of the NWs with the decrease of the length of the poly-crystalline segment and the enhancement of the effective magnetic anisotropy has been shown. Magnetization curves obtained from alternating gradient magnetometry experiments show that the average ME anisotropy results from the competition between the magnetic anisotropies of both crystalline segments of the NWs. Understanding the influence of size and confinement effects on the magnetic properties of nanocomposites is of prime interest for the development of novel and agile devices.
ABSTRACT
The round window was studied in normal adult and infant temporal bones to provide a knowledge base for the study of congenital anomalies of the round window, and to determine whether the round window develops postnatally. Fifty-three temporal bones were studied. Specimens were processed histologically, sectioned horizontally, stained with hematoxylin and eosin, and studied under the light microscope and microprojector. A special method of graphically reconstructing the round window was developed for this study, and was used to define the contour, area, and angle of the round window. We found that the round window is fan shaped. The area of the superoposteriorly located horizontal part (three-sevenths of the round window) and of the inferoanteriorly located vertical part (four-sevenths of the round window) totals approximately 2.29 mm2. In addition the angle between the plane of the tympanic sulcus and the vertical part of the round window was measured, and found to average 73.3 degrees. Lastly, the round window was found not to develop postnatally.