Magnetic hysteresis

About: Magnetic hysteresis is a research topic. Over the lifetime, 12665 publications have been published within this topic receiving 253100 citations.

Switching mechanisms in cobalt-phosphorus thin films

Abstract: Studies have shown that although the interactions between grains in magnetic thin-film recording media can enhance the squareness, these interactions are also responsible for media noise. The authors made measurements on Co-P thin films that give a simple and practical way of investigating the role of interactions in the magnetic processes that occur in these films. All magnetic measurements were made on a PAR 155 vibrating sample magnetometer with a resolution of 10/sup -5/ EMU. The field measurements were made with a Bell-Gauss Hall probe calibrated with a proton magnetometer to give an accuracy of >

Modelling hysteresis of interacting nanowires arrays

Abstract: Hysteresis loops of two-dimensional arrays of magnetic nanowires have been micromagnetically modelled. The calculations focus on magnetostatic interactions in addition to Zeeman and magnetic anisotropy energy terms. Starting from an ideally ordered hexagonal array, the generation of local disorder is first modelled and subsequently, hysteresis loops are calculated by Monte Carlo and iterative methods considering dipolar and higher-order multipole effects. The main conclusions of the modelling are: (i) distortion of the hexagonal ordering results in an increasing effective field to reach magnetic saturation while roughly maintaining coercivity, and (ii) an increase of the average distributed coercivity of individual nanowires gives rise to enhanced coercivity and anisotropy field. The results of these simulations are analysed in view of experimental loops of arrays of Ni nanowires filling nanoporous alumina membranes with different degrees of 2D-polycrystalline arrangement. After a careful analysis by image processing, it is concluded that fluctuations in the diameter and cross-section of individual nanowires play an important role in a deep correlation between modelled and experimental hysteresis loops.

Physical limits of hyperthermia using magnetite fine particles

Abstract: Structural and magnetic properties of fine particles of magnetite are investigated with respect to the application for hyperthermia. Magnetic hysteresis losses are measured in dependence on the field amplitude for selected commercial powders and are discussed in terms of grain size and structure of the particles. For ferromagnetic powders as well as for ferrofluids, results of heating experiments within organic gels in a magnetic high frequency field are reported. The heating effect depends strongly on the magnetic properties of the magnetite particles which may vary appreciably for different samples in dependence on the particle size and microstructure. In particular, the transition from ferromagnetic to superparamagnetic behavior causes changes of the loss mechanism, and accordingly, of the heating effect. The maximum attainable heating effect is discussed in terms of common theoretical models. Rise of temperature at the surface of a small heated sample as well as in its immediate neighborhood in the surrounding medium is measured in dependence on time and is compared with solutions of the corresponding heat conductivity problem. Conclusions with respect to clinical applications are given.

Study of diluted magnetic semiconductor: Co-doped ZnO

Abstract: We report on the high-temperature ferromagnetism in Co-doped ZnO films fabricated by the sol–gel method above 350 K. The lattice constant of c axis of wurtzite Zn1−xCoxO follows Vergard’s law for 0

Room temperature ferromagnetic properties of (Ga, Mn)N

Abstract: Dilute magnetic semiconductor GaN with a Curie temperature above room temperature has been achieved by manganese doping. By varying the growth and annealing conditions of Mn-doped GaN we have identified Curie temperatures in the range of 228–370 K. These Mn-doped GaN films have ferromagnetic behavior with hysteresis curves showing a coercivity of 100–500 Oe. Structure characterization by x-ray diffraction and transmission electron microscopy indicated that the ferromagnetic properties are not a result of secondary magnetic phases.