We report model calculations of the hysteresis loops of exchange-coupled ferromagnet/ antiferromagnet bilayers with monolayer-scale roughness and show that the loops are affected by the combined effect of the interface field strength, the degree of magnetic roughness and magnetostatic effects. The magnetization reversal may occur via domain-wall nucleation at the edges of monoatomic interface steps or coherent magnetization rotation. A magnetic phase diagram is constructed for a 10-nm-thick Fe film, subjected to nanometer-scale interface roughness.

We show that confinement in small volumes affects the interplay of exchange and dipolar interactions and the magnetic phases of hard and soft spherical core-shell nanoparticles. Large variations in the magnetization of thin shells may occur due to the core dipolar field gradient within the shell. The reversal field is tunable by the trends imposed by the dipolar and core-shell interface exchange energies. We show, for instance, that the reversal field of a CoFe 2 O 4 (30 nm)@MnFe 2 O 4 (6 nm) particle ranges from 15.5 kOe for antiferromagnetic coupling down to 2.5 kOe for ferromagnetic coupling.

We report a theoretical investigation of interface effects in the magnetic order of interface biased iron and Permalloy™ elliptical nano-elements. Contrary to intuition, there is a partial pinning of the interface layer, favoring double vortex states along the hysteresis loop. Interface biasing affects the relative chirality and the distance of the vortices. Unbiased nanoelements may nucleate vortex pairs with the same chirality separated by an antivortex. For interface biased nanoelements the vortex pair forms with opposite chirality separated by a magnetic domain.

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We report a theoretical study of the coercivity and bias of iron dots exchange coupled with an antiferromagnetic substrate. We show that flat dots, with height close to the iron exchange length, and lateral dimensions of a few exchange lengths, exhibit large enhancement of coercivity and exchange bias. For small interface field strength the magnetization reversal is nearly a coherent rotation with symmetrical loops. Interface pinning leads to large reduction in coercivity and asymmetrical loops, if the interface field strength is comparable to the value of the iron exchange field. We discuss the impact of geometrical confinement and interface pinning on the magnetization reversal mechanisms. We show that small area dots with height larger than the exchange length display stronger interface effects.