Coercivity and exchange bias near the compensation temperature for inhomogeneous Fe/Gd ferrimagnets

Abstract

We investigate the coercivity and exchange bias effect in Fe/Gd multilayers. Antiferromagnetically coupled (Fe 4 nm/Gd 4 nm)4 multilayer has a compensation temperature (Tcomp) of approximately 90 K. We observe that the coercivity of the inhomogeneous Fe/Gd ferrimagnet makes a local minimum near the Tcomp. When a 16-nm-thick Gd layer is deposited over a (Fe 4 nm/Gd 4 nm)4 multilayer, exchange bias emerges due to the interfacial interaction of the thick Gd overlayer and the Fe surface of the multilayer. Negative and positive exchange bias were observed below and above the Tcomp, respectively. In addition, there is a continuous transition from negative exchange bias to positive exchange bias across the Tcomp where coercivity makes the local minimum.

Anomalous temperature and interfacial‐coupling dependence of exchange bias in antiferromagnetic (core)/ferromagnetic (shell) nanoparticles

“…Recently, the reports on the sign reversal of H E due to the change in temperature in the systems, such as Co (FM)/CuMn (spin glass) bilayers [27], Fe (FM)/Gd (FM) multilayers [28], and the core/shell-type La 0.2 Ce 0.8 CrO 3 nanoparticles [29], have been steadily increasing. Nogués et al [30] studied the FeF 2 /Fe bilayer system and proposed qualitatively that one necessary condition for the occurrence of a positive EB is the AFM interfacial coupling.…”

MOKE study of Co/Ti/(Gd–Co) multilayers near the magnetic compensation state

“…7). Other authors [33] observed a local minimum of coercivity of the [Fe(4 nm)/Gd(4 nm)] 4 multilayer around the T comp indicating a difference between this multilayered structure and a homogeneous ferrimagnet (for the latter the coercivity diverges as 1/M s when the ferrimagnet goes through the T comp due to the vanishing net magnetic moment). The comparison of these two results confirms that, unlike RE/TM multilayers, Co/(Gd-Co) multilayers can be considered to be very similar to homogenous ferrimagnets.…”

Thickness dependence of oscillatory exchange bias

“…Since then various antiferromagnets (AF), which are exchange coupled to ferromagnets (F), have shown H EB [2][3][4][5][6]. There are well written reviews on the subject listing possible configurations [2,[7][8][9] and there are several theories [10][11][12][13][14] which give reasonable values in agreement with experiment.…”

“…Magnetic phase relations are currently under theoretical investigation to understand the exchange bias-like and training effects [39]. Previous experiments [5] showed that negative and positive H EB are associated with the Gd-and Fe-aligned states respectively. In Fig.…”