Influence of perpendicular magnetic field on angular dependent exchange bias of [Co/Pd]₅/CoFeB Electrodes

In perpendicular magnetic anisotropy (PMA) multilayers electrode system, the low spin polarization and large lattice mismatch between traditional PMA electrodes ([Co/Pt]_n, [Co/Pd]_n) and spin-filter barrier MgO make it difficult to obtain large tunneling magneto-resistance (TMR) ratio [1]. One of several possible solutions is to insert a magnetic electrode between MgO barrier and PMA multilayers electrodes, forming composite magnetic electrodes [2]. Therefore, it is critical to understand magnetic behavior of composite magnetic electrodes. Cain et al early found exchange bias like effect in NiFe/TbCo (FM-FM) bilayers [3]. They explained that tilt of spins at the interface between TbCo and NiFe is responsible for the observed exchange bias like effect. Recently, by applying a large in-plane magnetic field, B. Dieny et al initialized exchange bias in NiFe/[Pt/Co] (FM-FM) bilayer [4] and explained exchange bias like effect using closure domain model [5, 6]. People believe that closure domain formed at the interface is responsible for observed exchange bias. But few works were studied to figure out how perpendicular magnetic field affect closure domain and exchange bias like effect.