Abstract
Spin-orbit torques emerge as a promising method for manipulating magnetic configurations of spintronic devices. Here, we show that these torques can induce a magnetization reversal via domain wall propagation which may open new ways in developing novel spintronic devices and in particular in realizing high-density multi-level magnetic memory. Our devices are bi-layer heterostructures of Ni0.8Fe0.2 on top of β-Ta patterned in the form of two or three crossing ellipses which exhibit in the crossing area shape-induced biaxial and triaxial magnetic anisotropy, respectively. We demonstrate field-free switching between discrete remanent magnetic states of the structures by spin-orbit torques induced by flowing electrical current through one of the ellipses. We note switchings induced by the coupling between the ellipses where current flowing in one ellipse triggers a reversal in a neighboring ellipse which propagates from the center outwards. Numerical tools successfully simulate the observed coupling-induced switching using experimentally extracted parameters.
Highlights
Spin-orbit torques emerge as a promising method for manipulating magnetic configurations of spintronic devices
Following the birth of spintronics and the emergence of magnetic random access memory (MRAM) as a promising non-volatile and fast memory, focus turned into the search of efficient and scalable methods to manipulate the magnetic state of one of the magnetic layers in the magnetic tunnel junction (MTJ) which constitutes a basic two-level memory bit of MRAM
It was soon realized that this method is detrimental for the MTJ5, paving the way for the use of spin-orbit torques (SOTs) which utilize the effect that flowing a charge current in a heavy metal layer adjacent to a ferromagnetic layer generates a spin current flowing perpendicular to the heavy metal/ferromagnetic (HM/FM) interface into the FM layer without accompanying charge current[6,7,8,9,10]
Summary
Spin-orbit torques emerge as a promising method for manipulating magnetic configurations of spintronic devices. In a recent report[31] we showed the efficiency of SOTs in inducing switchings in structures which exhibit non-uniform magnetization and effective shape-induced bi-axial magnetic anisotropy These structures when used as one of the magnetic layers in a MTJ may pave the way for novel multi-level MRAM with efficient write operation based on SOTs. Here we show a new type of magnetization switching induced by SOTs. Commonly, magnetization switching induced by SOTs is studied where the entire studied magnetic device experiences the same injection of spin currents. The spin current affects only a small part of the structure; the magnetization reversal propagates away from the region subject to spin currents until a full switching is achieved Such type of reversal makes the switching of multi-level MRAM more efficient, but it paves the way for novel spintronic devices. We show switchings between discrete magnetic remanent states of the structures by flowing current through individual ellipses where the current flowing in the Ta layer generates torques on the
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