Dynamic selective switching in antiferromagnetically-coupled bilayers close to the spin reorientation transition

Abstract

We have designed a bilayer synthetic antiferromagnet where the order of layer reversal can be selected by varying the sweep rate of the applied magnetic field. The system is formed by two ultra-thin ferromagnetic layers with different proximities to the spin reorientation transition, coupled antiferromagnetically using Ruderman-Kittel-Kasuya-Yosida interactions. The different dynamic magnetic reversal behavior of both layers produces a crossover in their switching fields for field rates in the kOe/s range. This effect is due to the different effective anisotropy of both layers, added to an appropriate asymmetric antiferromagnetic coupling between them. Field-rate controlled selective switching of perpendicular magnetic anisotropy layers as shown here can be exploited in sensing and memory applications.

Symmetry-breaking interlayer Dzyaloshinskii–Moriya interactions in synthetic antiferromagnets

“…However, none of these contributions is able to create a biased switching in extended structures and under Bx only (26), requiring the IL-DMI as a symmetry-breaking mechanism. The reversal of CoFeB will be in reality strongly influenced by defects and inhomogeneities of the layers (27), and driven by domains of very small sizes for thicknesses around the SRT (28), making their direct observation using magneto-optical methods as those used here very challenging (25). Despite these, the macroscopic bias observed experimentally indicates that a clear reversal asymmetry for both branches is present.…”

“…The presence of IL-DMI has been experimentally investigated in our SAFs by making use of a magnetic field protocol that exploits the different reversal behavior of the two layers under vector magnetic fields (20,25). First, a strong unipolar -either positive or negative-(~0.4 T) Bz field is applied, saturating both layers, and defining the magnetic state of the Co layer for the rest of the field sequence.…”

Генерация неравновесных зародышей намагниченности в быстро нарастающем магнитном поле в синтетических ферримагнетиках Pt/Co/Ir/Co/Pt

“…Важной характеристикой, определяющей скорость работы датчика, является время отклика на изменение внешнего магнитного поля. В [11] наблюдалось значительное изменение формы петли магнитного гистерезиса асимметричного синтетического антиферромагнетика от скорости развертки магнитного поля, однако авторы не сообщали о неравновесных состояниях намагниченности в диапазоне скоростей развертки магнитного поля от 20 Oe/s до 40 kOe/s. Исследуемые в данной статье образцы отличаются от образцов из [11] тем, что оба ферромагнитных слоя имеют перпендикулярную магнитную анизотропию.…”

Critical switching curves of FeCoB synthetic antiferromagnets

“…In the static regime, SAF switching properties have been investigated by the method mentioned above. More recently, these properties have been studied by manipulating layer thick nesses to alter the layer switching order as a function of field sweep rate and direction [23]. Further, the microwave proper ties of SAF have been well investigated through ferromagn etic resonance (FMR) spectroscopy to characterize a number of features including linewidth, absorption position, coupling strength, intensity, angle and temperaturedepend ence of resonant absorption, and manipulation of resonant modes [24][25][26][27][28][29][30][31].…”