Exchange bias model for Fe/FeF ₂ : Role of domains in the ferromagnet

Abstract

Exchange bias (EB) is a shift of the hysteresis loop from its normal position, symmetric around H = 0, to H E = 0. It occurs when thin ferromagnetic (F) films are deposited on a variety of antiferromagnetic (AF) materials. EB is also associated with several additional remarkable features: i) the bulk magnetizations of the F is orthogonal to the AF easy axis; ii) H E is of similar magnitude for compensated and uncompensated AF interface layers; iii) the sign of H E can assume both positive and negative values; and, iv) the magnetizationwhere Hc is the coercive field. Here we propose a model that describes the EB phenomenon for a compensated interface. Based on the experimental evidence, and extensive computer simulations, we suggest that close to the Néel temperature a canted spin configuration in the AF interface freezes into a metastable state. As a consequence, the EB energy is reversibly stored in a spring-like magnet, or incomplete domain wall (IDW), in the F slab. The results we extract from our model, both analytically and through simulations, are qualitatively and quantitatively compatible with the available experimental information.

Large anomalous enhancement of perpendicular exchange bias by introduction of a nonmagnetic spacer between the ferromagnetic and antiferromagnetic layers

“…The actual value of H E could then be related to the energy stored in these partial domain walls in the FM, similar to what has been suggested by some recent exchange bias models. 18 Moreover, since FM-AFM exchange bias is mainly a short-range interaction, H E tends to exponentially decrease when increasing the nonmagnetic spacer layer thickness. 4 Hence, the curves presented in Fig.…”

Effect of Interface Roughness on Exchange Bias of an Uncompensated Interface: Monte Carlo Simulation

“…The last term describes the interfacial exchange coupling with an exchange constant, J INT , between the FM and AFM spins. The parameters used in this paper are taken from previous literature [18,19]. Our simulations are carried out using a Monte Carlo method with the Metropolis algorithm [20].…”

Origin of the Magnetic Proximity Effect

“…Moreover, Koon also showed that the magnetic moments in the AF interface layer exhibit canting; in fact, the minimum energy is achieved with the AF spins adopting a relatively small canting angle (0 < 10') relative to the AF bulk easy axis, with a component opposite to the cooling field Hld direction. However this canting, which is the manifestation of the MPE, has a significant magnitude only in the AF layer closest to the interface [21][22][23].…”