Angular Dependence Of Magnetic Properties Research Articles

Growth and Magnetic Characterization of 1D Permalloy Nanowires Using Self Developed Anodic Aluminium Oxide Templates.

1D Permalloy refers to arrays of nanowires (NWs) made of an alloy of Ni and Fe with 80 and 20 at% composition respectively. In the present work 1 D Permalloy NWs arrays were fabricated into the pores of self engineered Anodic Aluminium Oxide (AAO) templates by a simple electrodeposition technique (EDT). By varying the anodization voltage and parameters of the electrolyte solutions we developed AAO templates with different average pore diameters (40 nm to 70 nm) and developed 1D Permalloy NWs within them. Structural characterization of AAO templates and 1D Permalloy NWs were performed by Transmission and Scanning Electron Microscopy (TEM and SEM respectively). X-ray diffraction (XRD) studies of 1D Permalloy NWs showed their fcc crystalline structure and the AAO template was found to be amorphous in nature. Magnetic studies showed the 1D Permalloy NWs arrays to have strong shape anisotropy, and the easy axis was found to be parallel to the NWs axis. We studied the angular dependence of magnetic properties of the NWs. Coercivity (Hc) and remanence (Mr/Ms) measured along the NWs axis were found to be higher than those measured in a direction perpendicular to the NWs axis. 1D Permalloy NWs developed in this work have the potential to be used in magnetic recording devices.

Angular dependence of coercivity with temperature in Co-based nanowires

The magnetic behavior of arrays of Co and CoFe nanowire arrays has been measured in the temperature range between 100 and 300K. We have paid particular attention to the angular dependence of magnetic properties on the applied magnetic field orientation. The experimental angular dependence of coercivity has been modeled according to micromagnetic analytical calculations, and we found that the propagation of a transversal domain wall mode gives the best fitting with experimental observations.That reversal mode holds in the whole measuring temperature range, for nanowires with different diameters and crystalline structure.Moreover, the quantitative strength of the magnetocrystalline anisotropy and its magnetization easy axis are determined to depend on the crystalline structure and nanowires diameter. The evolution of the magnetocrystalline anisotropy with temperature for nanowires with different composition gives rise to an opposite evolution of coercivity with increasing temperature: it decreases for CoFe while it increases for Co nanowire arrays.

Effect of field cooling process and ion-beam bombardment on the exchange bias of NiCo/(Ni, Co)O bilayers

The research on exchange coupled ferromagnetic/antiferromagnetic (FM/AF) bilayers has been the foundation of spintronic applications such as hard disk reading heads and spin torque oscillators. In order to further explore the exchange bias behavior of NiCo/(Ni, Co)O bilayers, effect of field cooling process, magnetic angular dependence, and ion-beam bombardment was investigated. The difference in film composition resulted in remarkable distinction in crystalline structures and domain patterns. The exchange bias field (Hex) in the bilayer systems exhibited a strong angular dependence. The negative Hex after a field cooling process indicated that the polarity of Hex can be defined by aligning the magnetization orientation of the FM NiCo layer with the applied field. Moreover, enhanced exchange bias effect was observed in the NiCo/(Ni, Co)O bilayers that resulted from the surface of the (Ni, Co)O layers bombarded with different Ar+ ion-beam energies using End-Hall voltages from 0V to 150V. The interface spin structures as well as the surface domain patterns were altered by the ion-beam bombardment process. These results indicated that the exchange bias field of NiCo/(Ni, Co)O bilayer systems could be tailored by field cooling process, angular dependence of magnetic properties, and post ion-beam bombardment.

Anisotropic magnetic properties of bi-layered structure of ordered Co nanowire array: Micromagnetic simulations and experiments

The angular dependence of magnetic properties was investigated in Co nanowire (NW) array with varying length grown by pulse electrochemical route. In these investigations, three different NW lengths, 200, 400, and 1000 nm were considered. Detail structural investigation revealed the formation of hcp (002) texture for NW of length 200 nm. However, the existence of both hcp (002) and hcp (100) oriented texture was observed in longer NW of length 1000 nm. It was established that these two phases were well separated along the axis of the NW with lower segment having hcp (002) and upper segment with hcp (100) oriented texture. Micromagnetic simulation was carried out to correlate the experimentally obtained angular dependent magnetization reversal results with simulated data considering the different crystallographic structures as a function of NW length, and with the variation of angle between the applied magnetic field and NW axis. Inference was drawn from these correlations that the magnetization reversal occurs by coherent rotation in case of NW with sole hcp (002) structure, whereas vortex state formation plays an important role for hcp (100) structure. In case of bilayer structure, the interaction between these two states leads to a gradual crossover from a coherent state to a vortex one along the NW axis. Effort has also been made to explain the angular dependence of coercive field by micromagnetic simulation irrespective of the NW length.

A strong angular dependence of magnetic properties of magnetosome chains: Implications for rock magnetism and paleomagnetism

Single‐domain magnetite particles produced by magnetotactic bacteria (magnetosomes) and aligned in chains are of great interest in the biosciences and geosciences. Here, we investigated angular variation of magnetic properties of aligned Magnetospirillum magneticum AMB‐1 cells, each of which contains one single fragmental chain of magnetosomes. With measurements at increasing angles from the chain direction, we observed that (i) the hysteresis loop gradually changes from nearly rectangular to a ramp‐like shape (e.g., Bc and remanence decrease), (ii) the acquisition and demagnetization curves of IRM shift toward higher fields (e.g., Bcr increases), and (iii) the FORC diagram shifts toward higher coercivity fields (e.g., Bc,FORC increases). For low‐temperature results, compared to unoriented samples, the samples containing aligned chains have a much lower remanence loss of field‐cooled (δFC) and zero‐field‐cooled (δZFC) remanence upon warming through the Verwey transition, higher δ‐ratio (δ = δFC/δZFC) for the measurement parallel to the chain direction, and lower δ‐ratio, larger δFC and δZFC values for the perpendicular measurement. Micromagnetic simulations confirm the experimental observations and reveal that the magnetization reversal of magnetosome chain appears to be noncoherent at low angles and coherent at high angles. The simulations also demonstrate that the angular dependence of magnetic properties is related to the dispersion degree of individual chains, indicating that effects of anisotropy need to be accounted for when using rock magnetism to identify magnetosomes or magnetofossils once they have been preserved in aligned chains. Additionally, this study experimentally demonstrates an empirical correspondence of the parameter Bc,FORC to Bcr rather than Bc, at least for magnetite chains with strong shape anisotropy. This suggests FORC analysis is a good discriminant of magnetofossils in sediments and rocks.

Modelling the angular dependence of magnetic properties of a fully processed non-oriented electrical steel

Two different ways to approach the anisotropy of magnetic losses are compared, one of them based on texture and particles distribution and the other on a graphical subdivision of the hysteresis loss in two components. We have found an excellent quantitative correlation between the anisotropy of the “particles” and “low-induction” components, and a good qualitative correlation between the anisotropy of “texture” and the “high-induction” components.

Angular dependence of magnetic properties of 2% silicon electrical steel

In this work, we studied the anisotropy of the magnetic properties of a 2% silicon steel. Permeability, core losses, remanence and coercivity were analyzed in Epstein strips cut at 0°, 15°, 30°, 45°, 60°, 75° and 90° from the rolling direction. Coercive force monotonically increased from 0° to 90°, accompanied with a remanence decrease. On the other hand, a minimum in B 50 and B 25 was observed between 45 o and 60 o. This behavior can be explained by the steel sheet crystallographic texture, that shows a strong (1 1 0) [0 0 1] component, which develops the best properties in rolling direction (0 0 1) and is worse at 54°, where 〈1 1 1〉 lies. Losses behavior is more complex.

Implementation of vector moving Preisach model using texture coefficients as easy axis distribution

Vector moving Preisach model was applied to the untextured Co thin film media. The out-of-plane easy axis distribution of the particles was derived directly from the texture coefficient phkl obtained from x-ray diffraction analysis, which corresponds to the fraction of the grains that have {hkl} plane lying parallel to in-plane direction. In order to validate this variable, angular dependence of magnetic properties of CoCrPPt/Cr/glass thin films with two different composition was measured by using a vibrating-sample magnetometer. Simulated results showed little difference from the measured data.

Orientation and angular dependence of magnetic properties for Ba-ferrite tapes

It is shown that Ba-ferrite tapes have a different angle dependence for H/sub c/ and squareness ratio than acicular particulate tapes. Large perpendicular-to-longitudinal ratios for H/sub c/ and squareness, and small switching field distribution (SFD) values are expected to contribute to the excellent high-density recording capability of Ba-ferrite tapes. It is clarified that Ba-ferrite tapes composed of about 3.5 aspect ratio particles have smaller SFDr values over a range of squareness ratios in the longitudinal direction from 0.5 to 0.85 than conventional acicular particulate tapes. This means that Ba-ferrite particles are a suitable material for use in high-density recording media.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Angular Dependence of the Magnetic Properties of Steels Under the Action of Uniaxial Stress

ABSTRACTAngular dependence of structure sensitive magnetic properties such as coercivity and permeability has never been adequately explained by a quantitative physical model or theory. The present study investigates the angular dependence of magnetic properties of materials with different microstructures. Measurements were taken under compressive and tensile uniaxial stress. The materials investigated were plain carbon steels with compositions of 0.1 % -0.8% carbon. Alloy steels with compositions of 2.25 % Cr and 1.0 % Mo were also investigated. The effects of uniaxial stress on permeability along the direction of the stress can be described by including an effective field Hσ given by:Experimental results are compared to model using Hσ.