In order to investigate grain size effects on ferro–antiferromagnetic coupling in NiFe/FeMn systems, samples of glass/Cu zÅ/NiFe 75 Å/FeMn 150 Å/Ta 30 Å were made and the grain size of FeMn was changed by changing the Cu thickness z. Increasing z from 0 to 315 Å, the mean grain size increases from 18 to 50 Å. The blocking temperature, at which the coupling field NiFe/FeMn disappears, increases from 330 to 430 K with the increase of the mean grain size. The curve shape of the temperature dependence of the coupling field changes from a concave type to a convex type with the increase of the mean grain size. Temperature dependence of the coupling field were calculated using a thermal fluctuation model of antiferromagnet. The calculated curve of the temperature dependence of the coupling field agrees with the experiment qualitatively. However, the calculated curves of the temperature dependence of coercivity does not agree with the experiment.
The complementary nature of the exchange bias field and the coercivity enhancement in ferromagnetic (F) -antiferromagnetic (AF) exchange-coupled layer systems is explained based on an extended Fulcomer & Charap's model, in which the directional distribution of the easy axes plays a decisive role in governing the magnetization behaviors. The model was further extended to deal with the AF-layer thickness ranging from zero to infinity taking into account of NCel's spin fanning model. A comprehensive explanation of the influence of exchange coupling on the
magnetization behavior of the F-layer is given. It is shown that a rotationalAlthough there have been controversies about the microscopic mechanism causing the unidirectional anisotropy, the interfacial uncompensated AF-spins seem to be responsible for the manifestation of exchange biasing in most cases [4,5,6]. The enhancement of the coercivity, AHc, can often be understood as the effect of irreversible changes in the AFspin directions accompanying the switch of the F-magnetization, M. Other mechanisms, in which some incoherent magnetization process is taken into consideration, have also been proposed [7]. This paper will give a comprehensive magnetization procesi is inherent for the samples in which the explanation of the effect of the exchange coupling on the exchange coupling effect is dominant. The same model explains magnetization behavior of soft F-layers stressing the the temperature dependence Of the exchange bias field and complementary nature of Heb and H,. The role of AF-spincoercivity and the memory effect observed after annealing. The fanning along the thickness direction, the rotational nature of the magnetization reversal process and the temperature varieties of phenomena are mostly ascribed to the existence of distribution in the magnetic properties, net spin moment at the dependence of Heb and Hc will also be explored. AF-grain surface and AF-grain size.
The pinning field Hp (the amount of the shift of the hysteresis loops) and the coercivity Hc of the samples of the form glass/Ta 120 A/(Cu 100 A)/NiFe 75 A/FeMn 150 A/Ta 50 A increase almost linearly with decreasing temperature down to 20 K, below which Hc increases sharply. The observed strong positive correlation between Hp and Hc, seems to be reasonably explained by a combination of a newly developed model in which a directional distribution of the pinning field caused by a random distribution of the crystalline orientations in the antiferromagnetic FeMn layer is taken into account and Hoffmann’s ripple theory in which the local anisotropy is assumed to be proportional to Hp, although the sharp increase in Hc at very low temperatures remains to be explained.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.