Papers by Keyword: Magnetisation

Abstract: The Weiss model is extended by substituting the molecular field coefficient lwith a short-range-ordering coefficient g valid around and above Tc. The temperature variations of susceptibility of fcc Fe are calculated with a band model. Based on the above models, the phase equilibrium diagram of Fe-C binary system under a magnetic field is calculated.

Abstract: In this paper, the influences of depositing angles on TbFe film magnetic and magnetostrictive characteristics were discussed. TbFe films were deposited by DC magnetron sputtering. With the decrease of depositing angles from 900 to 150, TbFe film in-plane magnetization measured at 1600kA.m-1 external field is greatly increased. With the decrease of depositing angles from 900 to 150, the magnetostrictive saturation field is decreased. TbFe film in-plane magnetostriction is improved when depositing angles are changed from 900 to 150. Magnetic domain structures detected by MFM indicates that film easy magnetization direction is gradually changed from perpendicular to parallel with the decrease of depositing angles. The variation of film magnetic and magnetostrictive performances can be explained by the oblique anisotropy associated with columnar grain morphology of the films.

Abstract: 185 nm-thick Ni76Fe24 films were deposited on SiO2/Si(100) substrates at room temperature by DC magnetron co-sputtering and they were annealed in a vacuum of 5×10-4 Pa at 300 , 400 and 480 °C for 1 hour, respectively. The as-deposited film grows with thin columnar grains and has void networks in the grain boundaries. As the annealing temperature increases, the grain size gradually increases and the void networks decrease. Besides, the void networks shorten and widen with annealing temperature. The resistivity of the film decreases with increasing annealing temperature. The magnetic hysteresis loop of the as-deposited film shows a hard magnetization requiring a saturation field of 1050 Oe while that of the film annealed at 480 °C represents an easy magnetization. For the film annealed at 480 °C the coercivity is 78 Oe and the ratio of remanent magnetization to saturation magnetization is 0.72. The as-deposited and annealed films have an isotropic magnetization characteristic.

Abstract: In this paper, the spin configuration and the configurational anisotropy of the clusters were studied by Monte Carlo simulations. An easy magnetization directions and a configurational anisotropy were found for the clusters using the hysteresis and spin configurations in different magnetization processes, and the simulated natural angle and energy distribution. It is considered that the configurational anisotropy is mainly attributed to the non-uniformity in spin configurations.

Abstract: We have investigated the magnetic properties and magnetostriction of ZnxNi1-xMnSb compounds prepared by solid state reaction method. It is found that for x less than 0.6 the magnetization of ZnxNi1-xMnSb almost remains unchanged. However, when x is larger than 0.6 the magnetization starts to drop linearly. Experimental result indicates that at low Zn concentrations, x < 0.7, the Curie temperature (TC) decreases with increasing Zn concentration x. However, when x > 0.7, the Curie temperature increases distinctly with increasing x. The Zn concentrartion dependence of magnetostrictive ceofficient is also studied. The experimental curve shows that when x < 0.6 the value of magnetostriction coefficient for ZnxNi1-xMnSb decreases linearly with the increasing Zn concentration x. However, when x is above 0.6, the magnetostrictive ceofficient raises distinctly. By analyzing the XRD pattern, the structures of the materials are examined and the relationship between the properties and the structures are discussed. A structural phase transition is observed. It has been indicated that the structure plays an important role in the magnetic and magnetostrictive properties of the system.

Abstract: The effects of grain-size in La0.7Ca0.3MnO3-δ (LCMO) system have been studied in connection with the magnetic and electronic properties. LCMO system prepared by the solid-state reaction was annealed in air at 1200, 1300 and 1400°C. The grain sizes of LCMO samples become larger with increasing of annealing temperature (TA ). The magnetization in LCMO samples increased while the coercive field decreased with increasing TA. The conductivity increased and the metal-insulator transition temperature TM-I decreased with increasing of TA. These physical properties are due to the oxygen deficiency caused by the increase of grain size. Finally, it was found that the grain size and the mechanical connection between grains play an important role in determining the electronic and magnetic properties.

Abstract: The double perovskites Ca_2-xSr_xMnWO₆ (x = 0.0, 0.5, 1.0, 1.5, 2.0) have been prepared as pure phases by a conventional solid-state reaction process. Stoichiometric amounts of CaCO₃,SrCO₃, MnO and WO₃ were mixed, ground and calcined in a nitrogen atmosphere. X-ray and neutron powder diffraction (NPD), together with magnetisation measurements were carried out in order to characterise the materials. The NPD and magnetisation measurements, performed at different temperatures, were made in order to correlate the materials structural and magnetic properties. Susceptibility- Temperature (ϰ-T) curves were measured between 2K and 200K in field cooled (FC) and zero-field-cooled (ZFC) modes with an applied field (H) up to 3T. Rietveld analysis of NPD data shows that the samples were B-site ordered perovskites with different types of lattice symmetry. Magnetisation measurements at low temperatures indicate an antiferromagnetic ordering of the magnetic moments.