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Magnetization reversal in Ni/FeF 2 heterostructures with the coexistence of positive and negative exchange bias

2012; American Physical Society; Volume: 86; Issue: 22 Linguagem: Inglês

10.1103/physrevb.86.224414

1550-235X

Miroslavna Kovylina, R. Morales, A. Labarta, X. Batlle,

Metallic Glasses and Amorphous Alloys

Magnetization reversal mechanisms are studied in Ni/FeF${}_{2}$ heterostructures with the coexistence of positive and negative exchanged bias (PEB/NEB), showing single and double hysteresis loops (DHL) in magnetoresistance measurements. Micromagnetic simulations show that PEB and NEB domains of a minimum critical size must be introduced in order to reproduce the occurrence of DHLs. The simulations reveal that different magnetic configurations and, hence, different magnetization reversal processes take place in a ferromagnet (FM) on top of minority PEB domains that are either greater or smaller than the critical size. In particular, for the case of DHLs, core reversal of a depthwise domain wall is observed over minority PEB domains when the magnetic field is decreased from positive saturation. As the field is further decreased, a complex domain-wall evolution takes place in the FM, including the dependences of the domain-wall width and domain size on the magnetic field and distance from the antiferromagnet (AF). These effects should be taken into account when the domain size is estimated from data measured by depth-dependent techniques since they average the distribution of domain sizes in the FM for different distances from the AF.