Application Of Transverse Field Research Articles

Laser induced local modification of magnetic domain in Co/Pt multilayer

Manipulation of magnetic system by the use of laser has drawn the attention of contemporary research. We demonstrate here the modification of magnetic domain in perpendicularly magnetized Co/Pt multilayer by using ultrashort laser pulse. The as-prepared sample shows an out-of-plane saturation magnetic field of 803.4mT and almost zero remanence with a labyrinth-like domain pattern at room temperature. Atomistic simulation showed that interaction with femto-second laser results in demagnetization of the material in 200fs followed by a slower recovery. As it indicates a net loss in magnetization, so magnetic force microscopy is carried out to investigate the equilibrium state after the system is relaxed. Demagnetized random domains appeared at the centre of the laser spot with having a rim at the boundary which signifies a deterministic switching with respect to the neighbouring area. Rotation of domains at the central area with the application of small transverse field (100mT) proves the region to be magnetically weaker. Systematic 3D micromagnetic simulation has been performed to model the laser induced change by selective reduction of anisotropy which is discussed in detail. This shows shrinking of domains to a near circular pattern to minimize the magnetostatic energy. 50% reduction in anisotropy energy is observed with increasing the total energy of the system and a sharp increase in demagnetization energy also takes place simultaneously. This also satisfies the anisotropy in domain rotation with the application of transverse field.

Role of Bias Electric Field for X-ray Diffraction Intensity by TGS Crystal in Transverse Electric Field

X-ray diffraction intensity of triglycine sulfate single crystals influenced by the transverse electric field has been measured in the bias electric field. Polarity of domains in the sample can be judged by variation in intensity associated with polarity of the bias field. Polarity of the domains does not change by the bias field after prolonged transverse field application. There seems to be still positive domains even in the negative bias field and vice versa. Polarity of the domains seems to be randomly aligned without any relation to polarity of the bias field after the prolonged application.

Magnetoimpedance in La 0.67Pb 0.33MnO 3 manganite prepared by sol–gel method

In the present work, manganite La 0.67Pb 0.33MnO 3 was prepared by the sol–gel method. The difference between metal–insulator transition temperature T MI (217 K) and Curie temperature T c (342 K) in the sol–gel nanocrystalline manganite is mainly due to the grain boundary effect. The breaking of Mn–O–Mn bonds and strong scattering at the grain boundary cumber the transport. At room temperature 300 K, impedance and resistance increase with increasing frequency of ac currents. The observed dc magnetoresistance in sol–gel La 0.67Pb 0.33MnO 3 is related to the spin-polarized inter-grain tunneling and spin-dependent scattering at grain boundaries. The sol–gel manganite shows the magnetoimpedance characteristics, which are different from those of traditional sintered manganites and metallic giant magnetoimpedance materials. For sol–gel La 0.67Pb 0.33MnO 3 at low frequencies, the impedance experiences a peak under a low longitudinal field. In contrast, at high frequencies the peak phenomenon disappears, and the impedance drops sharply with low fields, which is due to the inter-grain or grain boundary effect. The permeability also sensitively varies with an application of transverse field. The magnetoimpedance effect in sol–gel nanocrystalline manganite is influenced by both field-induced permeability change and dc magnetoresistance.

Magnetic remanence properties of particulate recording media: comparison of barium ferrite with acicular materials

The magnetic remanence properties of barium ferrite particulate media were studied and compared with those of acicular particulate materials to understand better the differences in recording properties. The loss of remanence after the application and removal of an applied magnetic field was measured for fields opposite and transverse to the direction of initial magnetization. The loss of remanence after application of a reverse field gives information about the distribution of switching fields; this distribution is narrower in barium ferrite than in acicular materials. The loss of remanence after the application of transverse fields gives information about the magnetic anisotropy; barium ferrite is much more resistant to demagnetization by transverse fields than are acicular materials, but only in oriented media. All results are analyzed in terms of their dependence on relevant magnetic squareness parameters to account for the differing degrees of particle orientation in the samples and thus to observer fundamental differences in material properties. >

Creep in magnetic films, a phenomenological theory

A phenomenological theory of creep is proposed which relates the threshold for creep and the creep distance per cycle of applied transverse field to film material parameters. The model accommodates both quasi-static and dynamic effects. Key parameters in the theory relate to wall energy, material inhomogeneity, and the variation of wall contour, shape, and width with the application of transverse fields. The model assumes an abrupt creep threshold, a creep distance per cycle of transverse field which is typically a fraction of the wall width, and a creep distance per cycle of transverse field which is linear in the magnitude of the transverse field in the neighborhood of the threshold fields. A mechanical analog of the simple linearized theory has been constructed to demonstrate creep properties. In the model energetic binding of a wall to film inhomogeneities is replaced by mechanical friction, the energy storage properties of the walls by elastic bodies, and the driving fields by mechanical forces. The mechanical analog clearly demonstrates many of the aspects of creep.