Influence of demagnetization in remanence curves of magnetic thin films
Remanent magnetization curves of perpendicular magnetic thin films are simulated and measured. The simulations are used to investigate the theoretical influence of the strong demagnetizing field present in these films. Conclusions are drawn from this on how remanence curves should be measured and how they should be corrected for the demagnetizing influence. The experimental part consists of measurements on Fe‐Alumite, Co‐Pt–based multilayers, and Co‐Cr. In addition the latter material is also artificially patterned into microstrips in order to investigate the influence of demagnetization on remanence curves experimentally.
Magnetic relaxation process determination in the Co/Au nanoparticle system
Nonequilibrium magnetic dynamics has been investigated in the Co/Au bimetallic nanoparticle system. The system exhibits typical superparamagnetic behavior at higher temperatures and unequivocal hallmarks of magnetic relaxation process at $T\ensuremath{\sim}7\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. Since different scenarios of magnetic transition can be hypothesized here, detailed analysis of magnetization ac and dc experimental data has been performed. Specific methods have been employed in order to reveal the nature of the examined process. The observation of critical dynamics [power-law divergence of the relaxation time at ${T}_{g}$; dynamic scaling of ${\ensuremath{\chi}}^{\ensuremath{'}\ensuremath{'}}(T,f)$ data] and aging effects in the presence of strong interparticle interactions provide evidence that the system undergoes a transition to a super-spin-glass state rather than to a super-spin-blocked state.
Increasing pulp yield in kraft cooking of softwoods by high initial effective alkali concentration (HIEAC) during impregnation leading to decreasing secondary peeling of cellulose
Abstract Pulp yield can be improved by a more homogeneous delignification of the chips, achieved by improved impregnation prior to the cooking stage. Complete and efficient impregnation is obtained by increasing the diffusion rate by means of an impregnation liquor with a high initial effective alkali concentration (HIEAC). In the present study, the effect of HIEAC in the impregnation was evaluated and compared to a reference impregnation procedure and a prolonged impregnation. After the various impregnation scenarios, the alkali concentration was always adjusted to the same level in the beginning of the cooking stage. Impregnation with a HIEAC resulted in yield improvements by 1–1.5% units, due to a higher cellulose yield and possibly also to higher yield of glucomannan. The HIEAC with an even alkali distribution within the chips prior to the cooking stage resulted in a more uniform delignification carbohydrate degradation. Yield increase obtained by uniform delignification is due to both decreased shives content as well as less secondary peeling.