Current distribution and giant magnetoimpedance in composite wires with helical magnetic anisotropy

The giant magnetoimpedance effect in composite wires consising of a non-magnetic inner core and soft magnetic shell is studied theoretically. It is assumed that the magnetic shell has a helical anisotropy. The current and field distributions in the composite wire are found by means of a simultaneous solution of Maxwell equations and the Landau-Lifshitz equation. The expressions for the diagonal and off-diagonal impedance are obtained for low and high frequencies. The dependences of the impedance on the anisotropy axis angle and the shell thickness are analyzed. Maximum field sensitivity is shown to correspond to the case of the circular anisotropy in the magnetic shell. It is demonstrated that the optimum shell thickness to obtain maximum impedance ratio is equal to the effective skin depth in the mahnetic material.Comment: 23 pages, 7 figure

Determination of chlorophyll and carotenoids present in the seeds of the plant family apiaceae and the impact on seed quality

In this study, we assessed the content of chlorophyll a and b, β-carotene and lutein in seeds of carrot, celery, dill, parsley and parsnip commercial varieties by spectrophotometric method. It was determined that the content of chlorophyll a was higher than chlorophyll b and both differed significantly between plant species and varieties. The highest amounts of chlorophyll a, chlorophyll b, β-carotene and lutein were detected in parsley "Olomoucka dlouha". The lowest amounts of chlorophyll a, chlorophyll b, β-carotene and no lutein were detected in celery "Nuget", however, very low amount of lutein was detected in the parsley cultivars "Atika" and "Orbis". The content of β-carotene was higher than that of lutein in most varieties. The individual pigment contents were compared to seed quality parameters such as standard laboratory germination and seedling emergence. Negative correlation between energy of germination and pigments and positive correlation between seedling emergence and pigments in the parsnip and parsley varieties was observed. Determination the content of pigments and correlations observed the possibility to use spectrophotometry to evaluate the pigments present in the seeds as an indicator of seed quality.O

Temperature dependence of the coercive field in single-domain particle systems

The magnetic properties of Cu97Co3 and Cu90Co10 granular alloys were measured over a wide temperature range (2 to 300K). The measurements show an unusual temperature dependence of the coercive field. A generalized model is proposed and explains well the experimental behavior over a wide temperature range. The coexistence of blocked and unblocked particles for a given temperature rises difficulties that are solved here by introducing a temperature dependent blocking temperature. An empirical factor gamma arise from the model and is directly related to the particle interactions. The proposed generalized model describes well the experimental results and can be applied to other single-domain particle system.Comment: 7 pages, 8 figures, revised version, accepted to Physical Review B on 29/04/200